The Meat Animal and its Products Symposium documents... · CARCASS EVALUATION Beef, lamb and mutton carcass classification and grading in South Africa R.T. NAUDÉ, J.F.G. KLINGBIEL*

Proceedings6th Meat Symposium

The Meat Animal and itsProducts

25 April 1990

Contents

Introduction - The meat animal and its productsJ.H. HOFMEYR 1

Meat production and meat qualityH.R. CROSS 5

GROWTH MANIPULATION

The role of nutrition in integrated growth managementN. SLABBERT 19

Quantitative and qualitive aspects of beef production by some beef cattle breeds inthe RSA

J.F. DE BRUYN, R.T. NAUDÉ, J.H. HOFMEYR, W. BOK, J.A. VERMEULEN & M.C. BASSON* 41

The application of anabolic growth promoters for sheep under intensive feedlot conditionsP.E. STRYDOM, J.F. DE BRUYN, R.T. NAUDÉ, G.E. KRUGER & S.M. VAN HEERDEN 53

CARCASS EVALUATION

Beef, lamb and mutton carcass classification and grading in South AfricaR.T. NAUDÉ, J.F.G. KLINGBIEL* & G.G. BRUWER* 61

The development of a new classification system for pig carcassesG.G. BRUWER*, P.H. HEINZE, I.B. ZONDAGH, A. GEE** & R.T. NAUDÉ 77

PRODUCT QUALITY

Electrical stimulation and meat qualityP.H. HEINZE 93

Wholesale and retail packaging systems in the South African meat industryE.M. Scholtz 105

A comparison of the quality characteristics of goat and sheep meatH.C. Schönfeldt, R.T. Naudé, E. Boshoff*, S.M. van Heerden, W. Bok, M.C. Smit &L.S. Sowden 117

Proceedings of the 6th Meat Symposium: The Meat Animal and its Products25 April 1990, ADSRI, Irene, South Africa

2nd Revised Printing 21 October 2014

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SINCERE THANKS TO THE FOLLOWINGSPONSORS FOR THEIR GENEROUS SUPPORT

Bakke Packaging IMC Pitman-Moore

Blue Ribbon Meat Corporation Imperial Cold Storage (Renown Fresh Meat)

B T Enterprises Kanhym Fresh Meat

Checkers Meat Market Karoo Ochse

Crown Mills Meat Board

Darex Africa Red Meat Producers’ Organisation (RPO)

Enterprise Foods Rumevite

Eskort Bacon Co-op Supreme Meat Products

Freddy Hirsch Bizerba Scales The South African Agricultural Union

Haarmann & Reimer S.A. The Transvaal Pork Development Association

Hoechst S.A. (Animal Health) Woolworths

THE MEAT ANIMAL AND ITS PRODUCTS

J.H. HOFMEYR

Animal and Dairy Science Research Institute, Private Bag X2, Irene, 1675 Republic of South Africa

INTRODUCTION

The theme chosen for this symposium is much broader thanthat of the six preceding symposia held by the Institute. Thishas been done deliberately to make a clear statement on ourapproach to and philosophy on research relating to the meatanimal and its products.

We recognise and accept that research on the meat animaland its products must be aimed at improving the industry'sability to satisfy consumer demand. We believe that such aresearch programme starts on the farm with the predeterminedgenetic potential of the meat producing animal. It thenproceeds from conception, through growth and development,management, production systems, nutrition, along pre- andpost-slaughtering procedures, through the cold chain ofchilling, processing, packaging and displaying right up to theconsumers table.

Our scientists are, therefore, concerned with the interests ofthe producer, processor or manufacturer and the consumer. Ina highly competitive market this close link must be in themutual interests of those involved in the meat animal trade.

The future of the meat market lies in the improvement of thequality of the end product. Quality cannot be inspected intomeat - it has to be built in along the production and processingline.

Neither the time nor the occasion permits a detailedelaboration of the Institute's research on the meat animal andits products. However, research is such a critical element ofthe meat industry's production, education and promotion effortsthat a few comments in passing on the required research maynot be amiss.

MARKET INFORMATION

A centre of this kind should become more involved in obtainingmarket knowledge. Information on food markets here andabroad, and the policies and events which exercise significanteffects on the meat trade and product market is becoming ofmore importance in the formulation of domestic researchpriorities, production, marketing and pricing policy andstrategy.

Such a survey and impact study would require thedevelopment of a computer model. The model should alsoinclude by-products (hides, skins, tallow, carcass meal, blood,etc) to assist in forecasting demand, supply and prices. Moreinformation on by-products could induce greater investment inthis fifth quarter of the animal. This in turn, could be one of themost effective ways of ensuring a significant increase inincome and profitability to the producer and the industry.



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JAN HOFMEYR is the Director of the ADSRI, Irene. He was educated and trained at theUniversities of Pretoria and Uppsala (Sweden). He holds two honorary professorships - one inthe Department of Genetics and one in the Department of Veterinary Ethology. He has servedwidely on many scientific and research advisory committees within and outside theDepartment of Agriculture. He has represented the RSA at 18 International Congresses,Symposia and specialist meetings. He has been involved in several international projects andrepresents the RSA on four international organisations and one Regional body. He haspublished more than 100 scientific and popular scientific articles and technical reports. He ispresently President of the Joint Council of Scientific Societies of the RSA, President of the SAGenetics Society, Chairman of the Standing Committee for Animal Production of SARCCUSand Chairman of the Statutory Advisory Board for Animal Production.

IMPROVING EFFICIENCY OF PRODUCTION

The relatively low efficiency with which the ruminant meatanimal uses feed energy is the underlying biological reason forthe poor com-efficiency of animal populations is an increasedreproduction rate.

There are three major approaches which can be consideredindependently or combined to increase fertility in herds andflocks.

- Firstly, through the development or implementation of �im-proved or optimum environments� - this includes betterproduction and loss control systems, increased nutritionallevels, better herd health programmes, etc.

- Secondly, through the selection or creation of more suit-able (productive) genotypes for the �improved (optimum)environment�.

- Thirdly, through the judicious application of new reproduc-tion technology which has been proved to be functionallyeffective and financially feasible in practice.

Much more research work is required on delayed conception insome South African beef cattle breeds. Besides, basic geneticstudies could enable us to investigate the possibility ofdeveloping immunization against natural inhibitors, e.g.,inhibin, which causes delayed conception after calving. It isalso possible that immunisation in early life against gonadalsteroids may lead to accelerated sexual development andovarian function.

REDUCING HERD/FLOCK COSTS

Poor management has been identified in most cases as theunderlying cause for major livestock losses, low productionlevels and small profit margins. Remedial measures throughimproved managerial practices have been well establishedthrough research. However, in most instances, thedisproportionate increase in input costs in recent years hasoften proved prohibitive to the application of such methods.The most urgent research required here is the development ofsuitable models which would enable individual farm cost-analysis, offering alternatives with regard to availabletechnology and managerial procedures.

GENETIC SELECTION AND IMPROVEMENT

The main advantage of genetic improvement lies in itsfavourable cost:benefit ratio and the fact that the improvementis permanent.

Genetic improvement of any component of performance underany particular set of environmental conditions, is, therefore, an

effective method of reducing herd or flock production costs.Designing national breeding programmes for beef cattle andsheep to meet the demands of future production systems andmarkets is complicated for the following reasons-

In contrast to most other livestock, where production con-ditions and environment can be maintained within accept-able limits and where the existence of a universalgenotype is conceivable, this is not the case for beef cat-tle and sheep. The situation is further complicated by theexistence of negative correlations between important pro-duction traits - a major cause of contradictions and con-flicting breeding situations.

This topic is obviously one of the universally explored re-search avenues and the Institute has also been engagedin extended investigations on the subject for the past twoand a half decades. Much of the conceptual thinking andwork on the development of male and female lines in theindustry has been initiated by researchers of the Institute.The current work on sexual dimorphism in livestockbreeds offers a potential alternative for particular circum-stances.

The unique and diverse genetic pool in this country offersan excellent opportunity to identify sources of potentiallyvaluable genetic material for future genetic engineering.More support is needed to encourage and expand the ani-mal gene mapping work started recently here at the Insti-tute. This is important and necessary to facilitate genetransfer in the future.

RESEARCH AT ABATTOIRS

The erection of modern and well equipped abattoirs in theRSA has probably left many in the industry with the impressionthat little is left for further improvement in the pre- and post-slaughtering process.

Continued research is required on the following topics:

- Reducing bruising.- Humane and automated (robot) slaughtering procedures.- Fully automated carcass splitting, grading/classification(computer image processing techniques and measuringlean-to-fat ratios by absorption indices of microwave sig-nals, etc.) hot deboning, chilling, wrapping and packagingof beef, etc.

- Alternatives to messy and unaesthetic ink strip markinge.g., through possible laser or electric burn branding, etc.

- Automated monitoring, prevention of contamination andmethods of decontamination of carcasses at abattoirs.



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- Carcass surface coating to improve appearance, retainbloom, prevent loss through evaporation, dripping, etc.

- By-products have already been mentioned earlier but al-though abattoirs are involved in the handling of theseproducts there is little downstream processing. They pre-fer selling most of these products in a crude and earlystage and concentrate only on large volume, low value-added products such as meat meal, tallow, hides and of-fal. This leaves the by-product industry fragmented andwith a significant loss of potential income to the industry.

- Advanced processing offers excellent scope to the serumand cell culture industries.

Another problem at abattoirs are more cost-effective effluentand waste disposal methods.

IMPROVEMENT IN THE QUALITY AND

MARKETABILITY OF MEAT PRODUCTS

The modern food market is highly competitive and meat andits products will only remain in the market place if it is sold onquality, wholesomeness, safety, proper labeling and aestheticpresentation - all based on sound scientific information.

Consumer health sensitivity and demands for improved qualityof meat and meat products have already initiated manyresearch programmes on lean meat production and thepresence of certain polyunsaturated fatty acids which areclaimed to lessen heart disease in rats. Research appears tobe inadequate in the following -

- Methods in animal nutrition to manipulate the levels ofpolyunsaturated fats in meat.

- Notwithstanding all efforts to develop a practical and effec-tive measurement of tenderness - the most important qual-ity parameter of meat - we still cannot predict and meas-ure it for the consumer at the abattoir or counter.

- Although range-finished cattle are less exposed to anor-ganic and organic chemicals of some kind e.g., antibiotics,feedlot systems have increased the incidence of thesechemical residues in meat. A vocal minority of consumergroups have made this a sensitive issue in most countriesand the matter requires suitable action. Besides definingthe �problem�, the development of techniques to detectand accurately identify such substances in meat, is a mat-ter of priority.

NEW PRODUCTS

It is important to recognise the changing lifestyle of the urbanconsumer. The food market has lost its conservatism and newproducts are finding much greater acceptability than a decadeago. The meat industry must respond with products that meetnew consumer desires.

New market trends are developing e.g., fat-free meat,microwave fast food products, restructured meat products, etc.

These developments demand new research e.g., -

- new processing techniques;- new packaging methods;- improved storage life for refrigerated products, particularlyafter opening; and

- retention of colour stability, etc.

CONCLUSION

In order to understand the meat industry, it is necessary toappreciate the long chain of sequential and interrelatedprocesses which starts even before the birth of the meatanimal. This continues throughout the growth and finishingphases, slaughtering, handling, processing, storage, marketingright up to the final preparation for consumption. Research onthe meat animal and its products should, therefore, be plannedand conducted accordingly.

The best way to counter the increasing opposition andcompetition in the food market successfully is to design anational animal production strategy which is based on such asupportive, relevant and problem-orientated researchprogramme directed at the end-product. This should besupported by a dynamic system of information and technologytransfer to industry. It is also of the utmost importance thatmore effective communication and information systems beemployed to create public confidence in the wholesomenessand food value of meat and its products.

While conceding that many of the problems in the industry areso formidable that they demand major inputs and seriousefforts by scientists, there is sufficient reason to believe thatscientific developments and emerging technologies, will lead totheir solutions.



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N O T E S

MEAT PRODUCTION AND MEAT QUALITY

H.R. CROSS

E.M. Rosenthal Chair, Department of Animal Science, Texas A & M University, College Station,Texas, United States of America

INTRODUCTION

There is a golden rule in the food business that states, �If youare not consumer-driven, you will not survive!� I wouldguess that most of you would respond by stating that you areconsumer-driven and that you do respond to your consumer. Icould perhaps challenge you by asking a series of questions:

- Do you know what your consumer wants?- How does your consumer determine the value of product-price, taste, appearance, portion size, nutritional andsafety traits, convenience, etc.?

- Is this knowledge based on attitude studies and actual be-havior research, or do you just �know� your consumer?

- How many consumer segments do you have, and are youresponding to them?

- Have you changed any of your production systems to re-spond to changes in consumer demands?

- Are you being rewarded in the marketplace for producingwhat the consumer wants?

- Do you have a functioning value-based marketing systemthat is sending clear signals from the consumer back-grounds through the marketplace?

If your industry can answer �yes� to all of these questions,then you truly do have a consumer-driven industry. If youranswer is �yes�, you are in much better condition than the redmeat industries in the United States. We thought we had aconsumer-driven industry but had a harsh and rude awakeningin the 1970s. Perhaps it would be to your benefit if I were torelate some of the positive and negative experiences of theU.S. beef industry over the past decade. It all began with themeat boycotts in the late 1970s coupled with a sharp declinein the demand for beef.

U.S. INDUSTRY DILEMMA

Between 1977 and 1985, according to the National Academyof Sciences report, �Designing Foods�, 1 of 7 men and 1 of 8women in the United States stopped eating beef. In 1976 94,4pounds of retail beef disappeared per U.S. consumer; by 1988less than 70,0 pounds of beef were sold, per person, at U.S.retail outlets. Is something wrong with beef, as a food? TheBurger King Corporation, in 1987, after determining that 26 %of the U.S. population was eating less beef, surveyed thosewho had changed their consumption patterns. In the responseto the question, �Why have you reduced beef consumption?�the most frequent answer to Burger King's enquiry was �toavoid hormones/chemicals�. It is obvious that the U.S.



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RUSSELL CROSS is a Professor and Associate Head of the Department of Animal Science atTexas A & M University and is the current holder of the E.M. Rosenthal Chair in Animal andFood Science. He has been recognized for this leadership and research accomplishments. In1983 he came to Texas A & M University as Section Leader of the Meats & Muscle BiologySection. He was the leader of the National Consumer Beef Study which received majorsupport from the beef industry. His research is now concentrating on the value discoverysystem so that the proper value signal can be sent through the marketing chain in order forthe industry to avoid the continued overproduction of fat. He was also the co-project leaderwith Dr Antonio Gotto on the recently completed project to evaluate the effect of fat level inbeef, fish and chicken on lipoprotein profiles in humans.

consumer has changed - more, in the last dozen years, thanat anytime in history; the consumer is perplexed, confusedand, in some ways, frightened about foods and with respect torelationships between diet, nutrition and health.

It became obvious to U.S. cattle producers, about seven yearsago, that beef had to be repositioned in the diet and itsphysical and chemical composition changed, if its consumptionin desired quantity were to be reconciled with consumers'wants and wishes, with the recommendations of healthprofessionals, and with the plethora of advice (sometimessubtle; often scary) being offered by media personnel.

In 1983 the U.S. beef industry was faced with a dilemma. Witha food product that was out-of-vogue because it was too fat,the beef industry and its spokespersons had to (a) argue thatit is okay to eat more fat, (b) strive to reduce the fatness of itsproducts, or (c) give up on selling beef until cattle orconsumers (or their advisors - physicians, dietitians, scientistsor others in the health professions) had changed enough tocreate demand for the kind of beef the industry wanted to (andinsisted it must) produce. It quickly became obvious that (a)and (c), above, were not viable options - and so, fortunately,the industry moved rapidly, decisively and aggressively. Theyset about to modify the product, to reposition it in themarketplace, and to prove that beef belongs in the U.S. diet.The U.S. beef industry began its shift from a strictlyproduction-oriented business to much more of a consumer-driven industry. They began to ask the consumer what he/shewanted.

NATIONAL CONSUMER RETAIL BEEF

STUDY

The National Consumer Retail Beef Study (NCRBS),conducted jointly by Texas A & M University, the NationalCattlemen's Association (and sponsored by 29 state beefcouncils, 3 major packers, 2 breed associations and others),was an industry-wide research study aimed toward identifyingconsumer preferences for beef. The NCRBS found thatconsumers identified taste price, fatness and cholesterol asour most important factors in determining their purchases ofbeef. Consumers perceived the closer, or completely, trimmed(of fat) retail cuts of beef as being more appetizing, bettertasting and more nutritious (lower in fat and/or cholesterol).The most significant finding of the NCRBS was thatconsumers believed that beef products were too fat. Theconsumers' definition of leanness was related to �plate waste�and not to differences in marbling score or USDA qualitygrade. In that study, consumers purchased more beef, and thediet and health image improved, as more trimmable fat wasremoved.

As a direct result of the findings of the NCRBS, which werereleased in January, 1986, several national and regional retailsupermarket chains - most notably Kroger and Safeway -implemented closely trimmed (7 mm external fat maximum)programs for retail cuts of beef. A meat packer, the EXCELCorporation, reduced the amount of external fat (from theformer 20 mm, to a new 10 mm, average) left on the subprimalcuts of their �Perfect Trim� line of beef, and the NationalCattlemen's Association and the American Meat Institutepetitioned the USDA to �uncouple� the quality and yield grades(to allow the two kinds of grades to be applied independently)to make possible the removal of external fat from carcassesduring the slaughter/dressing operation.

Meanwhile, 81 % of U.S. citizens (according to studiesconducted by the American Meat Institute and the BeefIndustry Council) were trimming away all or some of the border(external or subcutaneous) fat from cooked beef beforeconsuming it, 86 % of U.S. food retailers were leaving no morethan 7 mm of external fat on beef cuts, and healthprofessionals were admitting that drastic reductions inconsumption of calories (from 480 to 134) and milligrams ofcholesterol (from 120 to 60) occurred if none of the 13 mm ofthe border fat surrounding a beef steak weighing 5,3 ounces(before trimming and cooking) was ingested (based on studiesby Texas A & M University).

Attempts by the beef industry to convince the U.S.Departments of Agriculture (USDA) and of Health and HumanServices (USDHHS) that existing food consumption data (andrecommendations to the public therefrom) were in errorbecause beef cuts at retail now had 7 mm, rather than 13 mm,of border fat were not successful. To determine whether therecent industry data was accurate (which said that the nationalaverage for fat thickness on retail beef was now 7 mm) andcould be substantiated, the USDA, NCA and BIC sponsoredthe National Beef Market Basket Study (NBMBS).

NATIONAL CONSUMER BEEF MARKET

BASKET STUDY

Conducted by Dr Jeff Savell and Dr Russell Cross of theTexas A & M University the NBMBS involved measuring thefatness of retail cuts followed by purchase of a prescribed listof retail beef items from 50 supermarkets in 12 cities (Seattle,Denver, Los Angeles, Dallas, Houston, Chicago, Detroit,Atlanta, Tampa, New York, Philadelphia, Washington, D.C.)and subsequent measurements of physical and chemicalfatness. Results of the NBMBS revealed that the averageborder-fat-thickness of beef cuts in the U.S. was 3 mm andthat there was, in 1988, 27 % less trimmable fat in the nation'scollective retail case than had been there in 1986. It was clearthat beef has �lost most of its ugly fat�. Unfortunately thoughmost of the loss has been occasioned by use of a knife



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(trimming away the excess portions). Following the release ofthe NBMBS, USDA agreed to revise its nutritional data onbeef. The revised Handbook 8-13 is due out this fall.

TASTE FAT vs WASTE FAT

The National Academy of Sciences, in 1985, formed acommittee called �Technological Options to Improve theNutritional Attributes of Animal Products�. One of the chargesof the committee was to investigate the role of fat in animalfood products in both palatability and nutrition. Jeff Savell andI were asked by the committee to explore the relationshipbetween fat (intramuscular) in beef, pork and lamb steaks androasts and palatability. Our goal was to find the least amountof fat that could be present in steaks and roasts beforepalatability would suffer. We also looked at the maximumamount of fat that could be present in red meat beforenutritional merit was compromised.

We looked at major grade-palatability studies conducted sincethe mid-1960s at the Texas Agricultural Experiment Stationthat primarily involved beef, but also included pork and lamb.Almost to a study, when intramuscular or marbling fat wasbelow 3 % (determined chemically) in raw meat, palatability ofbroiled rib and loin steaks, as evaluated by trained sensory orconsumer panels, dropped off sharply (In young beef, theredoes not seem to be a minimum amount of intramuscular fatnecessary for acceptable palatability in cuts from the chuckand round). When intramuscular fat increased above 3 %(minimum Slight marbling in minimum U.S. Select), there wasa slight increase in palatability with further thresholds occurringat 5 % (Small marbling or low Choice). We concluded that itwas necessary to have at least 3 % fat or minimum Slightmarbling to ensure acceptable palatability for broiling cuts fromthe middle meats - rib and loin; for markets that needed higherlevels of palatability, 5 % fat (for the Choice market) and 7 %fat (for the Prime market) were identified.

To determine the maximum amount of fat that could beincluded in steaks and roasts and still fit strict dietaryguidelines, we used the following information and assumptions:

(1) A 2 000 Kcal daily diet.

(2) According to the American Heart Association, no morethan 30 % of calories from fat (thus, 600 calories per dayfrom fat).

(3) Only 25 % (our estimate) of the calories from fat shouldcome from meat fat (thus, 150 calories per day from meatfat).

(4) Two servings (112 grams each, uncooked) from the meatgroup per day.

(5) 150 calories per day from meat fat divided by 9 Kcal pergram of fat = 16.6 grams of fat in meat per day.

(6) 16,6 grams of fat in meat per day divided by 225 grams ofuncooked meat per day = 7,3 % fat or mid-point Moderatemarbling (mid-point high Choice).

The �Window of Acceptability� chart was then constructed toshow the relationship between intramuscular fat andpalatability and to indicate the point where fat stops being anasset in taste and becomes a liability in nutritional merit. Eventhough the qualifications for the upper limit for maximum fat fornutritional merit are more severe than it would have been ifsmaller or fewer servings were used, the �window� is amplywide for most beef from U.S. Select through the mid-point ofhigh U.S. Choice to be used by almost everyone in the UnitedStates.

The �Window of Acceptability� concept has been demonstratedto the American Heart Association, the National Heart, Lung,and Blood Institute, numerous dietetic groups and has beenthe basis for establishing minimum and maximum fat levels forbeef products by the Nutritional Effects Foundation and forseveral private-label light or heart-healthy beef products. Beefcan be low in fat and still taste great. This window has beenaccepted by the beef industry as their �target� for the future.Enough fat in the muscle for taste, but no waste fat.

VALUE-BASED MARKETING

Following the dramatic fat reduction at the retail level, the U.S.beef industry was poised to respond to the retailer's demandfor a trimmed primal cut. That signal has not come from theretailer; thus, the packer has had no incentive to either trim theexcess fat or buy leaner (less outside fat) cattle. Becausethese value signals were not traveling from the consumer tothe producer, the industry is still producing a product (fat) thatthe consumer does not want. It was recognized by the leadersin the beef industry that the value-based marketing systemwas not functioning as it should be in a consumer-drivenmarket; thus, the U.S. beef industry formed the Value-BasedMarketing Task Force.

The U.S. beef industry has identified the study of �value-basedmarketing� as one of its highest priorities. The industry'sleaders realize that little progress will be made until theimpediments to a strong and viable value-based marketingsystem are removed. Value-based marketing could be definedas follows:

A marketing system that will encourage - at every stage ofproduction/distribution - a product with less trimmable fat.Because there is strong consumer preference for leaner meat,the beef marketing system must reward those who breed,



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feed pack, process, purvey and retail beef with minimalexternal/seam fat and optimal intramuscular fat - it must bevalue-based.

Because of the importance of this problem to the beefindustry, the National Cattlemen's Association and the BeefIndustry Council have formed a blue ribbon task force onvalue-based marketing. This 12-member task force iscomprised of the leaders from the seed stock, cow/calf, feeder,packing, foodservice and retail segments of the meat industry.Their charge is to identify the impediments to value-basedmarketing and identify research already underway orcompleted that can be used to remove these impediments.Their approach has been to begin with the consumer and workbackwards through the marketing system. Their task is justbeginning, but a few of the major impediments are listedbelow:

(1) Failure of the retailer to recognize value differences fortrimmer beef primal cuts. The retailer is currently sendinga weak signal to the packer to trim the fat.

(2) Average live trading where poor cattle are mixed with thegood cattle to yield an �average price�. The right kind ofcattle is receiving the discounts while the wrong kind is re-ceiving the premiums.

(3) Lack of an objective system to establish the value of indi-vidual animals/carcasses.

(4) Genetic predictors for carcass merit are not available.

To date, the task force feels that the most critical impedimentis the weak signal from the retailer to the packer. The taskforce agrees that work should begin to find solutions for all of

the major impediments since some will require more time andeffort than other (instrument grading and the genetics ofcarcass merit).

INDUSTRY TARGETS?

The U.S. beef industry now realizes that they have at leastthree major targets:

(1) Very High Quality Beef - U.S. Prime plus the upper halfof the U.S. Choice grade fits the needs of the hotel/restau-rant/institutional and food-service trades. The ultimate intaste and tenderness is deserved by those clientele whoare most able and willing to pay very high prices for ourproduct.

(2) Intermediate Quality Beef - U.S. Choice beef is featuredin 75 % of the retail markets in this country. The NationalConsumer Retail Beef Study demonstrated that there areconsumers willing to sacrifice some leanness in order toachieve the desired taste/texture of beef. The beef indus-try must strive for choice marbling in one-half to three-quarters of the feedlot cattle generated in the U.S. butwith far less external and seam fat than is generally pres-ent in carcasses of that grade.

(3) Acceptable Quality Beef - The National Consumer RetailBeef Study further revealed that there are consumers will-ing to sacrifice some taste/texture in order to be able topurchase leaner beef. Of the approximately 25 % of retailoutlets in the U.S. presently dealing in beef of less-than-Choice grade, almost all of them purchase �No-roll� car-casses. Unfortunately, the �No-roll� (not identified forUSDA quality grade) category can, and often does, con-



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FIGURE 1: Window of acceptability for fat in meat (palatability versus grams of fat (Two servings)) (Savell, J.W. & Cross,H.R., 1987. The role of fat in the palatability of beef, pork and lamb. National Academy of Sciences,Washington, D.C.)

tain beef of U.S. Select, U.S. Standard and U.S. Commer-cial grades; as a result it can be highly variable in eatingqualities. It is the hope of some in our industry that an offi-cial change in USDA grading nomenclature, exchangingthe name �Select� for �Good�, will encourage consumersto ask for it and retailers/restaurateurs to stock it. Selectgrade beef would provide slightly leaner beef than Choiceand would be more consistently �acceptable� in palatabilitythan is No-roll beef.

THREE PRIMARY TARGETS FOR

PROCESSED BEEF

Almost half of the beef carcass is presently sold as groundproduct or stew meat. Although that accomplishes the task ofmoving the product, it does so at a price - the lowest priceachieved for any retail-cut component of the carcass. It isimperative that research and development, science andtechnology make good the promise of value-added conceptsfor merchandising beef muscle. There is need to produce: (1)Finger Foods - The enormity of the McNugget (McDonald's)has not escaped the scrutiny of those who believe that thebeef industry must immediately launch into a campaign to dosimilar things with beef. �Grazers�, the name for consumerswho almost never eat a meal and who, instead, munch andsnack at all times of the day or night (�Grazers� are called�munchsters� in other circles), demand finger-foods and arequite willing to pay the price to procure them. (2) Snack-Foods- No snack food - ever - has had the impact that accompaniednational introduction of �fajitas�. A Tex-Mex snack food namedfor the Spanish word meaning �little belt� anddeveloped/merchandised originally in the Rio Grande Valley ofTexas was parlayed into �the� success story of the 1980s inbeef marketing. Use of an obscure, unobtrusive muscle fromthe short-plate or of the wing of the diaphragm muscle as fajitameat and effective, nationwide merchandising of the fajita as asnack food increased the value of average beef carcass in1986 by at least $2,50. This industry needs 3 or 4 �new�products, like fajitas, per year. The logical first extension of theconcept at retail has been the �stir-fry�. Identification of a newsnack food from beef amenable to promotion by a fast-foodfranchise has incredible impact on beef demand. (3) HealthfulFoods - The Louis Harris Poll in 1985 conducted for the FoodMarketing Institute revealed that 59 % of retail consumerswere �very concerned about nutritional content of foods� (fatswere perceived to be �a serious health hazard� by 40 % ofthose polled). The percentage of the U.S. population classifiedin the Yankelovich study of consumer segments as �Health-Oriented� increased by 7 percentage points (from 17 %, to24 %, of the total) between 1983 and 1985. Great clarity in adefinitive target emerges when it is realized that nearly 1 ofevery 4 U.S. consumers is health-oriented per se and thatanother 3 or 4 of every 10 in the population is �veryconcerned� about nutritional qualities of their food. It is

essential that we develop beef products with less total fat,saturated fat and/or cholesterol if we are to capitalize on thishuge potential market.

THREE PRIMARY TARGETS FOR NICHE-

MARKETING OF BEEF

Although the sizes of niche markets for beef are presentlyunknown and the subject of considerable controversy insideand outside the industry, such potential is well-documented inthe fact that U.S. citizens paid $1 billion for bottled water in1985. Several entrepreneurial operators have capitalized on atheme of targeting niche-markets and have made a real end-run on the more reticent in the beef industry. There is need toproduce: (1) Lite Beef - Consumers scared of fat, in fear ofcalories, and/or afraid of cholesterol will pay to avoid them, yetstill be able to eat a favorite protein source. Originallypromulgated by a breed association - Chianina - yetcapitalized upon first and foremost by an opportunistic, brightand brave producer - Roy Moore - �lite� (or �light� or �low-cal�,etc.) beef has found substantial demand and at a significantpremium. It is, unquestionably, in the best interest of the beefindustry, that lite beef be made available for consumers whomight not otherwise buy beef at all. (2) Natural Beef - The1984 Harris Poll for Food Marketing Institute determined that82 % of those surveyed were �very concerned� or �somewhatconcerned� about antibiotic and hormone residues in meat.That being the case, an innovative cattleman from Colorado -Mel Coleman - capitalized on what he perceived to be anpotential niche-market for beef by making certain that hiscattle, from conception to consumption, were never exposed toantibiotics (in subtherapeutic doses) or to hormone-containinggrowth promotants. His �Coleman Natural Beef� capitalized onthe ambiguity of what consumers think of the word �natural�and of what the government defines as �natural�, which aredrastically different, and developed a substantial market for hisproduct. The USDA has now developed programs wherebyvirtually all cattle feeders will be able to designate theiranimals as �residue-safe� and is presently seeking a means forclarifying regulations regarding use of the word �natural�;development of either or both as official, regulated protocolsmay well remove most of the steam from �natural� as aconcept amenable to promotion. Until such is, in fact, thecase, it is in the best interest of the beef industry to provide aunique product for residue-conscious consumers. (3) Beefwith Modified Fatty Acid Composition - When the currentcontroversy regarding dietary vs. medical intervention to lessenthe threat of disease settles out, which is likely to occur in thenext two years, it is most likely that the Public HealthApproach (universal dietary modification based onepidemiological data) will win out over the High-Risk Strategy(seeking out patients at high risk and modifying their riskfactors by appropriate medical intervention). If that is theoutcome, then all of the food industry must provide palatable



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choices of foods that are low in cholesterol, saturated fattyacids and total calories. The recent interest of the beefindustry in development of low-fat meat is an example of howthe food industry can alter its products in response to publiceducation about possible prevention of coronary heart disease,potential lessening of danger from colorectal cancer and,certainly, reduction of caloric intake for body weight control.Because consumers define leanness in terms of �plate waste�and not as differences in marbling, in as much as the amountof marbling is positively related to taste appeal of beef andsince taste appeal is the basis for popularity of beef in the diet,caution must be exercised in regard to how low we go inmaking beef leaner. (Savell and Cross of Texas A & MUniversity have recently described levels of intramuscular fat -marbling - associated with palatability/nitritional merit in beefthat will serve as useful industry guidelines to prevent beeffrom becoming �too lean� of �too fat�.) In general, people likethe taste of fat and, if possible, they would like to continue toeat it. One means to make that a reality would be to modifythe fat so that it contains fewer saturated fatty acids and moremonounsaturated fatty acids; the latter are neutral in terms ofpromoting incidence of coronary heart disease and cancer.Research must be conducted to identify genetic and/orenvironmental means for modifying fatty acid composition ofbeef so health professionals will feel comfortable inrecommending public consumption of such product.Development of beef with higher than normal content of oleicacid (a monounsaturated fatty acid) and lessened percentageof palmitic acid (a saturated fatty acid) would allow niche-marketing of a more healthful form of beef. After early attemptsby the entire beef industry to �play ostrich� on thediet/health/nutrition issues, there is presently considerableinterest in making/molding/modifying the product to fit real orperceived needs of a health-oriented population of U.S.consumers.

Which of the nine biggest markets for beef can be brought tobear specific kinds (breeds or crossbreeds) of cattle?Assuredly, kinds of cattle can be exploited to produce differentqualities of beef. The American Angus Association hastargeted �Very High Quality Beef� and capitalized on abilities oftheir breed to deposit marbling; their Certified Angus Beef(CAB) program has grown from a $5 million to a $40 millionbusiness in six short years. Success of the CAB programshould encourage Angus breeders to place extremely heavyselection pressure on their cattle to maintain and even toincrease the inherent ability to deposit marbling. Other breedswith genetic ability to produce heavily-marbled beef includeGalloway, Shorthorn, Brown Swiss, Jersey, Texas Longhornand, perhaps, Salers; the time is ripe for development of asynthetic breed based on crosses of Black or Red Angus withbreeds listed above to combine production traits, leanness andability to deposit marbling.

To satisfy needs for �Intermediate Quality Beef� for the taste-conscious retail supermarket trade will also require cattle withenough inherent propensity to deposit marbling that they willgrade 65-to-75 % Choice after 100-to-140 days of highconcentrate feeding. Obviously, breeds identified above - butalso specific line-strains of numerous other breeds (e.g., thereare data, including in some cases, USDA Carcass DataService records which reveal that there are groups of Brangus,Hereford, Simmental, Santa Gertrudis, Polled Hereford,Tarentaise, Charolais, Holstein and other breeds of cattle thatwill produce 65 % Choice carcasses) and crosses of specificbreeds (most notably the �black baldy� - Angus x Herefordcross - and the �gray smokey� - Angus x Charolais cross - butalso crosses of Angus with several other Exotic breeds, e.g.,Limousin, Chianina, Maine-Anjou, Simmental, Gelbvieh andothers) - will need to be propagated to produce IntermediateQuality Beef. If more cattle had �built-in� genetic potential todeposit marbling, the amount of fat in the carcass could becontrolled or manipulated through feeding and/or feeding time.

Production of �Acceptable Quality Beef� is, by far, the mosteasily attained goal in the U.S. beef industry; the majority ofour cattle - breeds and crossbreeds - fed appropriately, canproduce beef for the diet/nutrition/health-oriented, lean-conscious retail supermarket trade. Chianina breederscapitalized upon genetic leanness of their cattle in developing,and gaining label approval from USDA for, Key-Lite Beef.Because it is possible for cattle of nearly all breeds andcrossbreeds to be managed (on forage and/or grain diets ofappropriate duration and energy content) to produce lean, lightand low-cal beef, the cattlemen who will benefit most fromproduction of beef of this quality level (U.S. Select grade) willbe those who can do it 95 % or more of the time and mostefficiently (from a production cost standpoint). It must beemphasized, however, that not grading Choice and gradingSelect - 95 % of the time - are not equivocal. There are plentyof cattle that will produce carcasses of less than Choice qualitybut too often they will produce beef of Standard and evenUtility quality. That will not do! Remember - �AcceptableQuality Beef� is defined as that with 3 % intramuscular fat,Slight or more marbling, and grading at least U.S. Select asthe minimum; beef with 2,9 % or less fat in the muscles, tracesor practically devoid marbling, and grading U.S. Standard oflower won't usually be �acceptable� in flavour, juiciness andtenderness. Steers and heifers of almost all of the breeds andcrossbreeds mentioned above will, if managed properly,produce carcasses grading 95 % Select or higher but not all ofthem can do it efficiently or at a size large enough or, in somecases, small enough to fit the grade. Breeds with excellentpotential to dominate in efficient production of AcceptableQuality Beef from steers and heifers include Braler, Braford,Simbrah, Beefmaster, American Brahman, Charolais, Chianina,Limousin, Sahiwal and, perhaps, Piedmontese. Attempts toproduce young bulls (bullocks) that will grade Select or higher



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95 % of the time are likely to be successful only if cattle of�small�, or the lower half of �medium� frame sizes, are used;bullocks of �large� frame size will produce 40 % or higherpercentages of U.S. Standard grade carcasses at conventionalweights, and if fed to grade 95 % U.S. Select, their carcasseswill often exceed 900 pounds - far too heavy, by about 150pounds, for the retail trade.

There are many who believe that niche-marketing will increaseand that branded beef will replace federally graded product.That has already started to happen with both �lite� and�natural� beef being capitalized upon by a breed (Chianina)and/or two producers (Coleman and Moore). Certainly,production of �Lite Beef�, �Natural Beef� and �Beef withModified Fatty Acid Composition� can best be accomplished byproducers who are in control of the beef production sequence- through complete vertical integration or partial verticalintegration plus forward contracting - from conception toconsumption. There does not appear to be enough variabilityamong cattle in cholesterol content to attempt breed promotionof a low-cholesterol product; differences between breeds indegree of saturation/unsaturation of fat have not beenthoroughly researched, but modification of fatty acidcomposition by feeding changes by genetic engineeringappears to be plausible and, assuredly, worth trying toaccomplish. �Lite Beef�, �Natural Beef� and �Beef with ModifiedFatty Acid Composition� can be produced using cattle of any -and every - breed or crossbreed; all that is needed is theknowledge and desire to do so.

Likewise, �Finger Foods�, �Snack Foods� and �Healthful Foods�can be made from muscle of any of the breeds or crossbreedsof cattle. It is in the best interest of the entire beef industry totry to produce all three of these forms of processed beef, but itis not likely that specific producers of specific breeds orcrossbreeds of cattle would be able to corner such market orcapitalize upon a concept of product-form for a long-enoughperiod of time to make pursuit of that means for merchandisingtheir beef worthwhile.

There are at least nine specific identifiable U.S. markets forbeef and approximately 70 breeds and innumerablecrossbreeds with which to produce beef to fit a targetedmarket. For 7 of the 9 markets, production of beef to fit thetarget is not impacted by breed; production of �AcceptableQuality Beef�, �Lite Beef�, �Natural Beef�, �Beef with ModifiedFatty Acid Composition�, �Finger Food�, �Snack Food� and�Healthful Food� is not likely to be in the exclusive purview ofany breed or crossbreed of cattle. Only the 2 markets whichare based on genetic ability to deposit fat as marbling - �VeryHigh Quality Beef� and �Intermediate Quality Beef� - areamenable to breed exploitation because there is no knownway to cause cattle to deposit marbling if the genes to causethat to happen are not present. For breeds of cattle that wish

to play in the entire ball game (all 9 markets) rather than three-quarters of it (7 of the 9 markets), it seems logical that theywould seek out, find and perpetuate lines or strains of cattle inthat breed with the ability to produce Choice carcasses. In allcases, however, the low-cost producer of a commodity forwhich there is substantial demand can survive and prosper.

SAFETY CONCERNS

Food safety is an essential element of quality and is ofparticular significance to modern consumers. Despiteprocessors' increasing ability to ensure safe food, consumerscontinue to have concerns about certain aspects of foodsafety. Consumers tend to be concerned about things theycannot see, smell or taste; as a result, they feel they have littlecontrol over things such as residues and microorganisms.Since 1984, �residues, such as herbicides and pesticides�,have been the leading answer to this type of question. In 198982 % of all shoppers considered residues to be a �serioushazard� and another 16 % considered them to be �somewhatof a hazard� - total of 98 %.

In the November, 1988 report of the Food and DrugAdministration Pesticide Program, Residues in Foods - 1987,is the conclusion: �Under the Total Diet Study, 936 foodsamples representing the diets of U.S. consumers wereanalyzed. The dietary intakes of pesticides were, in almost allcases, less than 1 % of acceptable levels set by Food andAgriculture Organization, World Health Organization�. DrCatherine Adams of FSIS, USDA, describing the NationalResidue Monitoring Program said, �In 1988 300,000 tests weremade, involving 400 chemicals; less than 1 % exceededF.D.A. tolerances, and F.D.A. tolerances have a 100-foldmargin of safety�. Dr Sanford Miller of the University of TexasHealth Science Center in San Antonio in 1989 said, �Theresimply is not a public health problem with pesticide residues.The real risks in the food supply are microbiological hazards�,actual risk for illness from microbes is 1 in 100, while risk ofillness from pesticides is 1 in 1 000 000�. Dr Frank Young,Commissioner of the Food and Drug Administration, in a 1989interview, stated, �Pesticides are perceived by many people asthe most dangerous health issue but contamination withmicrobes is much more important than are chemical/toxicresidues.�

Of those surveyed for TRENDS-1989, 61 % consideredantibiotics and hormones in poultry and livestock a serioushazard and another 26 % considered them something of ahazard - a total of 87 %. While the FMI study suggests a highlevel of concern about such issues, that study is based on�aided response� data in which the problem is specified anddegree of concern is then registered. In corollary studies byFMI involving �unaided responses�, in which consumers areasked to identify items of concern to them about red meat,



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13 % mention concerns about antibiotic and hormoneresidues.

According to Amy Barr of the Good Housekeeping Institute,scientists rank food safety hazards in the following order,illustrating that scientists' beliefs and the public's perceptionsare not always in agreement: (1) Microbiological, (2)Nutritional, such as over-consumption or poor food choices, (3)Environmental contaminants, (4) Natural toxicants, and (5)Hazards from pesticide residues or food additives. In the FMIstudy �microorganisms� were not given as an item forconsumers to equate in terms of concern.

�Safety� came to the fore with cyanide in a couple of grapes,Alar on some apples, front-cover publicity by TIME andNEWSWEEK articles in the spring of 1989 and the publicparanoia that causes rats and actresses to dictate U.S. foodpolicy. Nevertheless, such hype is cause for substantialconcern when realization of the impact and importance ofconsumer perception comes home to roost in the hearts andminds of those in the beef industry. That product, toot, isvulnerable. U.S. Representative Charles Stenholm (Dem-TX)has said that issues of food safety will be to the 1990s aswere issues of diet/health/nutrition in the 1980s in determiningthe mind-set and food selections of U.S. consumers. A 1987article (�Dangerous Chemicals in Meat�) in Gary Null'sNATURAL LIVING NEWSLETTER heightened consumeranxieties about potential problems with �antibiotics in animalcare, hormone treatments, pesticides, misapplication of animaldrugs and what animals eat� (items identified in that treatise).Of the 38 % of respondents to the TRENDS-1989 survey whoreported that they avoided certain foods �for safety reasons�,meat/red meat was the single most-often avoided food (by24 % of those who avoided some food). Such behavior pointsout that - with regard to food/meat/beef safety issues - there is�perception and there is �reality� and that the crux of thematter for long-term repositioning of a food in the diet centersupon making certain that facts (science-based) effect thesolution and decide the case.

The USDA's Meat and Poultry Hotline received a significantlyhigher number of enquiries about foodborne illness in 1987than in previous years. Call appeared to be directly related tomedia reports about foodborne microorganisms (e.g., 60MINUTES' report on Salmonellae in poultry). Consumers haveconcerns about foodborne microorganisms, but they are morelikely to direct those concerns toward food handlers - overwhich they have no control - such as restaurants and foodprocessors, than they are toward their own food-handlingpractices, where they have significant control.

Most experts agree that the U.S. has the safest (and mostabundant) food supply in the world. But, said Dr CatherineAdams (Food Safety and Inspection Service, USDA) in 1989,

�Perhaps we've done too good a job of convincing U.S.consumers that we have the safest food supply in the world ...because now they abuse it - especially with temperatureabuse�. In an article entitled �From Kitchen to Table� in TIMEmagazine (March 27, 1989) consumers were cautioned aboutproper refrigeration and handling of meat and mayonnaise;yet, later in that article, they say, �but, ifpackers/processors/retailers would do a better job - keepingpathogens off the meat in the first place - consumers couldhandle it inappropriately without fear of the consequences�.

The meat-packing industry is making great strides in the latterarena. Dr Rod Bowling of Con-Agra recently reported that theMonfort of Colorado, Inc. plant at Greeley, Colorado, had -from 1984 to 1989 - reduced total bacteria on beef cuts by80 % and reduced pathogens (Listeria, Salmonella, E. coli,Yersinia, Campylobacter, S. aureus and Clostridia) by 95 %.Dr Bowling attributed 90 % of their success to employment ofGood Manufacturing Practice and 10 % of their success to useof acetic acid sprays. Good Manufacturing Practice in beefslaughtering/dressing protocol emphasizes prevention ofcontact of the dressed carcass with hide, hair, feces orgastointestinal tract contents, in as much as those are theprimary sources of food pathogens. Rinsing of the carcass witha weak solution of an organic acid (like acetic acid - theprimary functional component of vinegar) kills some bacteriaand injures other bacteria, yet cannot be tasted or smelled bythe consumer of the end product.

The most commonly reported foodborne illnesses are causedby bacteria. Ironically, these are also the easiest types offoodborne illness to prevent - by thoroughly cooking foodsto destroy bacteria, by keeping raw and cooked foodsseparate and by refrigerating cooked food promptly inshallow containers.

Even though food-borne illness is by admission the greatestfood-safety threat, it is interesting to note that Dr David A.A.Mossell of the University of Utrecth (Netherlands) hasquantitated relative risks of death - to the average person, incomparison to the risk of death from Salmonellosis at 1 in 100million. Does that mean the beef industry should not worryabout keeping food pathogens off of beef? Not on your life.Constant vigilance must be maintained to reduce bacterialcontamination on beef during slaughter/dressing, fabrication,wholesaling and retailing.

The issue of antibiotic residues in beef is very poorlyunderstood by consumers. There is little or no dangerassociated with ingestion per se of antibiotics that might occurin beef; the danger is that in feeding antibiotics to livestock,certain strains of pathogenic (to humans) bacteria will developthat are resistant to that antibiotic. If a human then wasexposed to those resistant strains of bacteria, he/she could not



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be treated with that antibiotic for therapeutic purposes. Nodocumented case of such occurrence has even beenauthenticated.

Centers for Disease Control (in 1986) tracked a case in theMidwest and the news media reported �The smoking gun atlast? A new study points the finger at antibiotics in meat -again�. Because of public concern over this issue, then-President of the National Cattlemen's Association - Jo AnnSmith - urged U.S. cattle feeders to stop feedingsubtherapeutic-levels of antibiotics. And, they did (97 to 99 %of them by industry estimates). Shortly thereafter, however,four research studies conducted at either Harvard University ofLoma Linda University reaffirmed safety of subtherapeutic useof antibiotics in livestock. And in February 1989 the NationalAcademy of Sciences issued a report on subtherapeutic use ofantibiotics in animal feed stating that �there is no directevidence (this practice) creates an excess risk of disease ordeath in humans� and �The study (made at the request ofFDA) was unable to find data directly implicating thesubtherapeutic use of feed antimicrobials (antibiotics) in humanillness.� Nevertheless, the nation's cattle feeders have notresumed the practice of feeding low levels of antibiotics incattle rations.

Anabolic agents (some of which are steroid-type hormonessuch as estrogen) are sometimes implanted into the surface ofthe ear of cattle to effect repartitioning of energy consumed bythe animal so that more muscle, and less fat, is deposited. Asa result of that process, the average amount of estrogen isincreased in a 3-ounce serving of beef from 1,2 nanograms(one nanogram is a billionth of a gram) in a sample from anon-implanted steer, to 1,9 nanograms in a sample from asteer that was implanted (100 or so days prior to slaughter).When it is realized, however, that the average, nonpregnanthuman female produces 400 000 nanograms of estrogen eachday by normal physiological body processes, the increasedbody-load of estrogen occasioned by eating 3 ounces of beeffrom an implanted steer (total of 400 001,0) vs eating 3ounces of beef from a non-implanted steer (total of 400 001,2)is of no physiological or medical consequence to theconsumer. No documented case of any problem associatedwith ingestion of meat from an animal implanted with ahormonal repartitioning agent has ever been documented.

Present consumer fear of use of growth promotants in beefproduction arose when the European Community (EEC)banned importation of beef from the USA on grounds of ouruse of anabolic steroid hormones. In truth, the EEC - drowningat the time in excess beef - used the hormone issue to createa non-tariff trade barrier to preclude importation of our beefinto those 12 countries. Since imposition of the �EEC hormoneban�, a committee of scientists appointed by the EEC (andchaired by Professor Eric Lamming of the United Kingdom),

Codex Alimentaires, and the Food and AgricultureOrganization of the World Health Organization have all goneon record as stating, �there is no risk to the public health orwell-being as a result of properly administered growth-promoting, anabolic steroid hormones to beef cattle�. F.D.A.routinely monitors animal-food products for drug residues (inparts per million, billion and trillion); in 1987, beef topped thelist as the most residue-free meat.

NUTRITION

Average estimated U.S. ingestion of cooked beef and cookedred meats, per day, has been determined by Breidenstein andWilliams of the National Live Stock & Meat Board and is 25 g(Light Users), 60 g (Moderate Users) and 100 g (Heavy Users)for beef and 42 g (Light Users), 115 g (Moderate Users) and215 g (Heavy Users) for all red meats. Nutrient contribution oftotal cooked red meat ingestion in the diet of the average U.S.user amounts to the following percentage of the recommendeddietary allowances (RDA): 47 % for protein, 17 % for calories,25 % for iron, 31 % for zinc, 23 % for thiamin, 12 % forriboflavin, 28 % for niacin and 73 % for vitamin B-12. Redmeat is considered to be �nutrient-dense�, if muscle portionsonly (and not the deposits of external and seam fat) areconsumed - that is, for the amount of calories consumed(17 % of the RDA), the trade-off in protein (47 % of the RDA),vitamins (12 to 73 % of the appropriate RDA) and minerals (25to 31 % of the appropriate RDA), identified above, makes it ahighly desired source of essential nutrients in the diet. Again, itmust be emphasized that U.S. consumers, on average, do notconsume �too much� red meat or beef per capita per day. Ifconsumers will eat only the �red� (the muscles) and avoideating the �white� (the visible depots of fat), they will benefitimmensely from intake of essential nutrients at a very modestexpense in calorie intake.

Nutrient composition of beef cuts (100 gram portions,separable lean only) can be stratified by cut and USDA grade(or for ground beef - by leanness). For consumers who wish toreduce intake of calories and/or percentages of calories fromfat or from saturated fatty acid, cuts can be selected by grade,or exchanges between cuts can be made, or leaner kinds ofground beef can be chosen. As examples, (a) choosing Selectrather than Prime, top round steak would reduce calories by14 %, total fat by 39 % and saturated fatty acids by 40 % if100 grams of each were consumed, (b) eating 100 grams ofextra-lean, rather than regular, ground beef would save 9 % incalories, 11 % in calories from fat, 19 % in total fat and 19 %in saturated fatty acids, and (c) consuming eye-of-round steakrather than rib steak, both from the Choice grade, wouldreduce caloric intake by 21 %, total fat intake by 50 % andsaturated fatty acid intake by 55 %. Variations among kids ofbeef cuts allow the consumer to select different entrees fromwithin the bovine species that suit his/her requirements; it is



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not necessary to change species-origin (from beef to fish orchicken) to obtain meat of the desired nutrient and/or caloriecomposition.

It is difficult to compare nutrient composition of beef vs chickencuts because of differences in method of preparation andcookery, and because of lack of comparability in anatomicalorigin and parts actually eaten. Nevertheless, data in Table 1provide some insight regarding how beef (when only themuscle, and none of the visible deposits of fat, is eaten)compares to chicken (skin on or skin off, battered of not, friedor roasted); but, however it is prepared, all of it is eaten interms of four critical energy or lipid components. If the chickenbreast (without skin and roasted) is compared with either beefrib steak or top round steak (separable lean only and broiled),chicken has decided superiority in caloric content, total fat andsaturated fatty acids - with no appreciable difference incholesterol. On the other hand, if one compares chickenbreast, prepared by Kentucky Fried Chicken personnel (withskin, batter-dipped, fried), with beef top round steak (separablelean only, broiled), beef has decided superiority in caloriccontent, total fat and saturated fatty acids but it containsalmost 10 % more cholesterol. Suffice it to say that chicken vsbeef comparisons must be made on �apple:apple� bases forthe results to be meaningful; it is unfair to compare chicken inits worst light, to beef in its best light, or vice versa. It isimportant to note, however, that most people are nowingesting only the lean portions of a beef steak while far fewerpeople eat skin-off roast chicken. If the latter were true - andmost who eat chicken prefer it skin-on and fried - beef standsup well in the comparison.

For the present, U.S. cattle producers are taking comfort fromthe fact that their industry has changed the face of its future bymaking revolutionary - not evolutionary - changes in thefatness of beef products as they appear at the retail market.Dietitians, too, can be comfortable that by recommending toconsumers that if they eat the red (muscle) and not the white(fat), they can have their cake (enjoy beef's great taste) and

eat it too (without fear of diet/health/nutrition consequences).The beef industry now produces steaks, roasts and groundbeef that are contemporary in calorie-content.

CONVENIENCE

For more than 100 years, the component parts of the beefcarcass have been merchandised in four classical retail-cutforms - as steaks, roasts, stewing beef, or ground beef. To besure, there are broiling steaks, frying steaks and braisingsteaks, there are oven roasts and pot roasts, and there isground chuck, ground loin, ground round, ground beef(�regular� and �lean� and �extra-lean�), hamburger and even�Hamburger Steak�. Still the four classical forms are steaksand roasts, stewing beef and ground beef.

More than half of all married women now work outside thehome. Children lead extraordinarily active social lives. Morefathers travel extensively as a part of their job. The erosion ofthe family unit has resulted in more informal dining - fewerscheduled, sit-down, formal dining situations - and more�grazing� by a generation of �munchsters� has become thenorm. Consumption of away-from-home, fast-foods is growingand becoming progressively more acceptable as a regularmeal source; purchase of fast-foods for consumption off thepremises, at home (now 40 % of all fast-food sales) haveincreased dramatically as V.C.R. ownership and availability ofrental movies have soared. (People rent a movie, buy take-outfood and go home, rather than eating out). Convenience andpreparation ease have become critical components of mealplanning at home. Innovative and aggressive marketing offrozen foods, seafoods, poultry and pork (which has recentlydisassociated itself from red meat by proclaiming that it is �theother white meat�) has caused these industries to grow at theexpense of red meat consumption. Most recently, microwaveoven penetration - now at more than 70 % of U.S. households- has caused consumers to be assaulted with non-beefmicrowavable finger-food, entree, snack and complete-mealitems.



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CALORIES (kcal) TOTAL FAT (grams) SATURATEDFATTY ACIDS

(grams)CHOLESTEROL

(milligram)Choice Beef1, Rib Steak, broiled 233 13,55 5,70 82Choice Beef1, Top Round Steak, broiled 194 6,45 2,26 84Chicken Breast2, With Skin, batter-dipped, fried, from Kentucky Fried Chicken 336 20,94 5,76 76Chicken Breast2, With Skin, batter-dipped, fried, from USDA

Handbook 8-260 13,20 3,52 85

Chicken Breast2, Without Skin, roasted 173 4,51 1,27 851 Separable lean only2 As eatenSource: �Designing Foods�, National Academy of Sciences (1988)

TABLE 1: Nutrient composition per 100 grams of beef steaks and chicken breasts.

Almost half of the beef carcass is presently sold as groundproduct or stew meat. Although that accomplishes the task ofmoving the product, it does so at a price - the lowest priceachieved for any retail-cut component of the carcass. It isimperative that research and development, science andtechnology, make good the promise of value-added conceptsfor merchandising beef muscle.

Beef must be made progressively more convenient, to store, toprepare and to eat - if it is to measure-up to the competition. Itdoes not do that at present, and beef is falling progressivelyfarther behind in the matter of convenience of its productforms. The fajita is the beef industry's single success inpopularizing a finger-food.

�Competitively priced� is not synonymous with �cheaper� oreven �comparably priced�. U.S. consumers are quite willing toweigh quality and value and price so that for improved,enhanced or increased �quality� they perceive greater valueand understand that price will be commensurately higher.Obviously, that is why a BMW automobile can be equated ascompetitively priced in relation to a Buick and competitivelypriced with a Hyundai; they're not the same price, but theprice:value relationships are understandable, equitable andcompetitive.

With that in mind, beef does not need - necessarily - to sell forthe same price as chicken, if the eating experience associatedwith ingestion of a filet mignon is sufficiently superior to thepleasure occasioned by eating a drumstick. To be certain thatbeef maintains (and builds upon) its historic inherentsuperiority in perceived value, it is essential that the tasteperformance of bovine muscle be exemplary, 99 % of the time.

Most of the research relating beef palatability to livestockproduction practices suggests need to feed cattle for about100 days on a high-energy diet (usually, corn) prior toslaughter to assure that the resulting product is flavorful, juicyand tender. Most of the scientific studies relating ultimatecooked-beef palatability to carcass traits suggests strongrelationships between youthfulness and amount of marbling(intramuscular fat) and flavor, juiciness and tenderness. Fortaste performance to be exemplary in almost every eatingexperience, beef must come from cattle that have been fedright and be from a youthful animal with reasonably highpropensity to deposit marbling. At present, beef of the U.S.Choice grade (requiring a marbling score of �Small� and anintramuscular fat content of about 5 to 7 %) is the appropriatetarget for nearly all of the HRI and FS trade and for probably75 % of sales in supermarkets. Experience suggests that beefof that grade performs well (on the palate) in the appropriatesetting - in the home or in a restaurant, as a snack or entreeitem - and has perceived value commensurate with price.

There is strong present demand for beef of premium quality,and at a premium (to U.S. Choice beef) price. In 1989, 35million kg of Certified Angus Beef was sold to retail and foodservice outlets, and three other kinds of premium quality beef(Sterling Silver, Chef's Exclusive, Granada Certified Beef) arestrong forces in that market. Consumers have demonstratedwillingness to pay substantially higher prices for a morepleasureful eating-experience; such hedonism may result fromeither or both of the food quality of the environmentalatmosphere. If beef is to assure itself a place in suchexperiences, the very best beef products must be directed tothose markets that can capture and benefit from the addedvalue that accrues when people are �dining� and not just�eating out�. Repeat sales of high-priced food items will occuronly if product-performance is truly unique and/or substantiallysuperior to the average for that type of product. That being thecase, purveyors of premium quality beef depend on veryyouthful and highly marbled beef - average Choice to highPrime - to service needs for that clientele.

Price per kg of product in the retail case can be confusing tothe shopper and has deterred toward beef retail cuts with noexternal fat appearing in the marketplace. One hundred andfifty grams of muscle surrounded by an external covering of fatthat is 20 mm thick would sell for $9.00/kg, while that samequantity of muscle surrounded with 13 mm or 7 mm or zeromm of external fat might sell for $10.80, $12.60 and $14.40.Such increases in apparent cost cause �Sticker Shock� (thepsychological aversion by consumers to the apparently higherprice) and reluctance to purchase such an �expensive�product. Sticker Shock is very real and has been the majordeterrent to complete removal of external fat from all beefretail cuts (most retailers have moved, in progression, to 7 mmand then 3 mm fat-trim levels, to cushion the blow ofincreasing prices). Price per serving comparisons betweencuts with differing amounts of external fat reveal far lessdisparity in total cost per serving because as fat is removed,the cost per pound increases but the weight of the cutremaining goes down.

Beef is, depending on the quality-level desired and the amountof fat that can be tolerated, competitively priced. To remain�competitive� in price, beef must maintain a perception of realvalue that warrants its higher �real� price. That cannot occur ifboth waste fat and taste fat are removed in over-zealousattempts by industry to reposition the product only by making itprogressively more lean.

Nevertheless, in the summer of 1989, a panel of economistsreported to the National Cattlemen's Association that beef willfall farther behind alternative sources of animal protein (e.g.,poultry and pork) unless dramatic improvements can be madein efficiency of beef production, processing and marketing.



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CONCLUSIONS

When the U.S. beef industry decided to shift to a consumerdriven industry, they were a bit naive. They had little idea as towhom their consumer was or what they wanted. They arelearning rapidly. They are learning that there is no �one�consumer. They are learning that their product is not perfect.They have learned that if you wish to known what yourconsumer wants in regard to product, ask them, not someother segment of the marketing chain. This learning processdid not come cheaply to the U.S. beef industry. TheCattlemen's Beef Board has spent at least $20 000 000 in thepast five years on product and market research. At present,

their research budget is over $9 000 000 each year. Butresearch is only part of the answer - the various industrysegments must begin to implement the key findings of theseresearch studies.

Much of what I have discussed with you today is likely notnew. I suspect that your research laboratories and variousprivate sector companies are making similar investments andasking similar questions regarding their consumer. My closingadvice is again - if you are not consumer-driven, you probablyshould not be in the food business. Seek and ask yourconsumer and you shall learn. Be prepared to respond to thedemands of your consumer.



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17

N O T E S



18

N O T E S

THE ROLE OF NUTRITION IN INTEGRATED

GROWTH MANAGEMENT

N. SLABBERT


INTRODUCTION

Increasing consumer demand for high quality lean beef (VanNiekerk, 1989) and the sideways movement in red meat pricesover the short to medium term due to the probable surplus inred meat up to 1996 (Meat Board, 1990), stresses the needthat the primary objective of the beef industry must be theefficient production of high quality lean carcasses. Economicproduction of red meat in South Africa will require thedevelopment and application of marketing orientatedproduction strategies. This will require greater lean tissuedeposition throughout the production cycle and the redirectionof feed energy from fat to protein growth, through all phases ofgrowth. This can be accomplished only where availabletechnology is integrated to effectively manage growth. Thejudicious application of nutritional strategies play an importantrole in such an approach.

The major production trend currently is towards the use ofcattle of a larger mature size (large frame size) which usuallygain more rapidly and fatten at a heavier mass. The positivefeed margin within the growing feedlot industry during recentyears and the resulting differential pricing structure for differentframe types of feeder calves (Ford, 1988) stimulated this trend.Although the demand of the feedlot industry for feeder cattle ofa larger frame size is the traditional method of increasing lean

beef production, this can be in direct conflict with the nutrientrestrictions of natural pastures in many extensive productionareas. The extensive beef producer needs an adapted small tomedium frame type cow (small to medium mature mass) toachieve a regular and high calving rate (Meaker, 1988). Theprimary producer can maintain or improve herd cost efficiencyby using terminal crossbreeding (large offspring from smallbreeding animals) and by modifying patterns of growth in cattleto produce more beef from the breeds and/or cattle types(frame sizes) adapted to specific production environments. Thesecondary producer (feedlot industry) on the other hand mustmainly concentrate on the latter approach together with properfeed formulation and management to maximize feed marginsfrom all cattle types available.

This review concentrates mainly on the potential to manipulatethrough nutrition the composition of growth of growing animalsto market mass. Nutritional related methods to improve feedefficiency in intensive and semi-intensive production situationsare briefly discussed.



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NEETHLING SLABBERT is responsible for beef cattle nutrition research at the ADSRI, Irene.He received his BSc (Agric) Hons from the University of Pretoria and is presently registered atthe same University for his MSc degree. His research interests include feed grain processing,grain utilization in feedlot diets, growth and feed intake studies with beef cattle and limitfeeding of concentrate diets.

FACTORS INFLUENCING BODY

COMPOSITION

The current beef carcass grading system in South Africaaccepts 18 % carcass fat as the biological optimum amount offat (Klingbiel, 1984). This places an upper limit on the range ofcarcass fatness in which growth manipulation can take placewithin certain age classes (A, B, C). Visual evaluation of theamount and distribution of subcutaneous fat is an importantcomponent of the grading system, with the 5,0 cmsubcutaneous fat thickness measurement (5,0 cm off themidline of the dorsal aspect of the carcass at the junction ofthe 10th and 11th thoracic vertebrae) as a point of reference.Due to variability in this subcutaneous fat covering, the limitsfor fat thickness to obtain the traditional optimum grades ofSuper A, Prime B and Top C, are set between 3 and 7 mmsubcutaneous fat (Klingbiel, 1984). The upper limit of 7 mmcorresponds to a carcass fatness of about 21 %.

An understanding of how cattle grow is required to manipulateand identify the optimum slaughter stage (desirable ratio ofmainly muscle to fat) (Naudé, 1974; Berg & Butterfield, 1976)and to use nutritional management strategies effectively.These tissues (muscle:fat:bone) grow at different rates(patterns) and achieve their maximum growth rates at differentstages of maturity (Berg & Butterfield, 1976).

The quantity of fat in the empty body is equal to that of proteinwhen the fat content is between 17 and 19 % (Garrett, 1980).After this equilibrium is reached the fattening phase beginsand fat is deposited at an increasing rate while the protein isdeposited at a decreasing rate. Factors such as nutrition,breed (genotype), sex, growth promotors and compensatorygrowth can influence the mass at which this occurs. Fat is themost variable tissue in the body and manipulation of carcasscomposition depends largely on controlling the proportion andrate of fat deposition (Berg & Butterfield, 1976; Byers, 1982a,1982b; Robelin & Geay, 1983).

Nutrition

For most of the different breeds in South Africa an optimumslaughter mass on a typical feedlot diet for early-, medium-and late maturing genotypes (Naudé, 1982; Naudé et al.,1986) has been determined. However, little attention has beengiven to the extent to which nutritional factors such as dietaryprotein to energy ratios and concentrate to roughage ratios inthe diet, and feed intake levels, can be used to manipulategrowth and therefore live mass, at the point of optimumfatness.

Relation between protein and energy intake

With inadequate dietary protein intake, protein deposition isrestricted and extra energy is available for lipogenesis whichincreases the % carcass fat and decreases the efficiency ofgrowth (Campbell, 1988). Although a deficient protein intakecan have a measurable influence on the body composition ofbeef cattle, these differences are small and do not appear toinfluence the commercial value of the carcass (Garrett, 1978).However, a protein deficiency depresses growth rate(Tritschler et al., 1984; Abdalla, 1988; Newbold, 1988) to agreater extent. The NRC (1984) calculated that each gram ofdietary protein deficiency should decrease protein depositionby 1,7 g and rate of gain by about 10 g per day. In the studyof Tritschler et al. (1984) the steers fed a diet with 20 % lessnitrogen than the diet on which a maximum daily gain wasobtained, had a 32 % lower empty body gain. This resulted ina lower body mass over the same feeding period. Tissuegrowth can be increased by raising the protein concentrationof the diet or by increasing feed intake. In both cases theresponse is related to an associated increase in protein intake.A moderate protein deficiency influences body compositionand efficiency primarily through a decrease in the growth rate.

A lower body mass and thus also a lower lean tissue massdue to an earlier moderate protein deficiency, can be regainedcompletely in a realimentation phase of sufficient length, dueto compensatory growth (Martin et al., 1978, Merchen et al.,1987; Abdalla, 1988). However, care should be taken toprevent a protein deficiency during this realimentation periodwhich will increase the proportion of fat (Kauffman, 1978). Amore severe earlier deficiency, however, increases the fatproportion of gain due to a decrease in protein gain and thusdecreases the body mass where an optimum level of fatnessis reached.

With adequate dietary protein intake the partitioning ofenergy between protein and fat synthesis is determined by therelationship between energy intake and protein deposition(Black & Griffiths, 1975). The linear model proposes that leantissue growth is constrained primarily by energy intake. Thisimplies a linear change in energy deposited as fat and protein(Tyrrell et al., 1974 and Geay, 1984, as cited by NRC, 1985).Further proposals range from an asymptotic maximumdeposition of protein (Byers, 1982a), to a linear-plateaurelationship (Campbell, 1988), to a maximum proteindeposition followed by a decrease (Anrique, 1976, as cited byNRC, 1985). There is however, limited support in the literaturefor the various response relationships between energy intakeand protein deposition (Campbell, 1988).

Campbell (1988) suggested that growing ruminants, becauseof their inherently low appetite, cannot consume sufficientenergy to fully express their genetic potential for lean tissue



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growth and therefore operate essentially in the linear phase.Under these circumstances raising energy intake results in anassociated linear increase in the rate of deposition of fat,water, protein and ash and thus in growth rate. For animals inwhich the relationship between energy intake and proteindeposition is linear any factor which reduces feed intake or theutilizability of dietary energy will limit lean tissue growth.

In situations where feed intake capacity is sufficient in relationto protein deposition potential, lean tissue growth is restrictedeither by energy intake or by factors intrinsic to the animal. Onthe other hand, where energy intake of an animal is sufficientto maximize protein deposition any extra energy supplied isdeposited as fat, resulting in an overall decline in the rate andefficiency of growth and a marked increase in body fat content(Béranger, 1978; Geay & Robelin, 1979; Byers, 1982a, 1982b;Fox & Black, 1984). However, there is evidence (Campbell,1988) that lean tissue deposition is influenced by factors suchas live mass, sex condition, genotype and growth promotors orinteractions between them.

Dietary energy concentration

In Table 1 recent results of Slabbert & Campher (1989,unpublished data) illustrate to what extent terminal carcasscomposition (protein, fat and bone), of Zeranol implanted,medium frame weaner steers is influenced by divergent dietarytreatments at an equivalent carcass mass. A decrease in

concentrate to roughage ratio (80:20 to 30:70) corrected forlevel of intake, significantly decreased the percentage carcassfat from 19,1 to 14,8 % in a quadratic manner (P<0,01). This isin agreement with research reported by Bond et al. (1972),Byers (1982a), Meissner et al. (1982b) and McCarthy et al.(1985). A decrease in level of feed intake (ad libitum to 80 %ad lib), corrected for dietary energy concentration, significantlydecreased carcass fat content from 18,8 to 16,3 % (P<0,01) ina linear fashion. This agrees with results of Byers (1980a,1980b) and Byers & Rompala (1980).

Although the effect of divergent dietary treatments onpercentage carcass muscle (Table 1) is less pronounced thanfor carcass fat percentage, a decrease in concentrate toroughage ratio (80:20 to 30:70) corrected for level of intake,significantly (P<0,01) increased percentage carcass musclequadratically from 63,3 to 65,8 %. This is in agreement withresults of Bond et al. (1972) and Meissner et al. (1982b). Adecrease in feed intake level (ad libitum to 80 % ad libitum)significantly (P<0,05) increased the percentage carcassmuscle in a linear fashion from 63,5 to 64,4 %.

From the above mentioned discussion and results of Byers(1982b) and Lemieux (1988) it is clear that the effect ofvarying the feed intake level within the same diet has effectson carcass composition similar to that of varying dietaryenergy concentration. This indicates that the effects of level ofnutrition on composition are more related to energy intake per



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CONCENTRATE: ROUGH-AGE

ITEM FEED INTAKE LEVEL ROW AVERAGE

Ad lib 90 % Ad lib 80 % Ad lib80:20 Fat % 21,7dm 17,6an 17,8an 19,1a

Muscle % 61,4am 64,9dn 63,6an 63,3a

Bone % 16,6ax 17,0x 18,1dy 17,2a

55:45 Fat % 20,1ex 19,5bx 17,7ay 19,1a

Muscle % 62,8a 62,9e 63,5a 63,1a

Bone % 16,7am 17,2mn 18,2dn 17,4a

30:70 Fat % 14,5fm 16,5an 13,3bm 14,8b

Muscle % 66,2b 65,1d 66,3b 65,8b

Bone % 18,66mn 17,8m 19,5en 18,6b

COLUMN AVERAGE Fat % 18,8x 17,9y 16,3zMuscle % 63,5x 64,3xy 64,4yBone % 17,3m 17,3m 18,6n

1 Based on prime rib cut (Naudé, 1972); Cold carcass mass (203 kg) as covariate.Means in a column within an intake level with different superscripts abc differ (P<0,01Means in a column within an intake level with different superscripts def differ (P<0,05)Means in a row within diets with different subscripts mn differ (P<0,01)Means in a row within diets with different subscripts xyz differ (P<0,05).

TABLE 1: Estimated carcass composition of medium frame steers on divergent dietary treatments at an equal carcassmass1 (Least square means) (Slabbert & Campher, 1989 unpublished data).

se rather than to specific feed ingredients included in the diet.Suggestions of effects of grains vs forages on fat deposition(Smith et al., 1984) and of specific carbon sources onlipogenesis (Prior & Scott, 1980) have also been reported. Atthe same empty body gain steers fed a high grain diet tendedto have a higher fat gain than steers fed a forage diet (Smithet al., 1984; Lemieux et al., 1988) which is most likely due todifferences in substrate absorption. However, from Table 1 andresearch results of Reid et al. (1968), Byers (1980a, 1980b),Meissner (1983a, 1983b), Old & Garret (1987) and McCarthyet al. (1985) it is evident that carcass composition (carcassmuscle to fat) is not always affected by feed intake levels anddiet effects. The probable reason for this controversy toregulate the composition of the carcass by nutritional means isdue to the relationship between rate and composition ofgrowth.

The growth study of Slabbert & Campher (1989, unpublisheddata) where different growth rates were achieved with mediumframe steers by using different concentrate to roughage ratios(80:20; 55:45 and 30:70) and different feed intake levels (adlib; 90 en 80 % of ad lib) gives an indication of the relationshipbetween mean growth rate and composition of growth. Asindicated in Figure 1 muscle gain increased at a decreasingrate with an increase in carcass gain, while fat gain in-S forexample, significantly increase daily empty body protein gain(both rate and physiological limit) from 18 to 30,8 % and from24 to 46 % respectively, relative to non-implanted steers(Lemieux et al., 1988; Loy et al., 1988). This implies that at thesame carcass fat content (%) implanted animals have a highercarcass mass. Although anabolic growth promotors can differ

in their growth rate response (De Bruyn et al., 1984; Lemieuxet al., 1988; Loy et al., 1988; Meaker & Barnard, 1988) and intheir repartitioning potential (Unruh, 1986; Lemieux et al.,1988), the actual difference in the extent of repartitioningincreases with an increase in the rate of growth (Figure 2) andthus on the amount of energy available to be redirected fromfat deposition.

Body mass

There is a strong tendency for an animal to achieve a certaincarcass composition at a given mass. However, from theprevious discussion it is clear that the composition at a certainbody or carcass mass within a certain frame type, sex and/orgrowth promotor, is largely a function of rate of growth (Byers,1982b; Meissner, 1983b; Rompala et al., 1985). This meansthat elevating rates of gain would change body composition ata given mass only if the composition of gain is changed.Composition of gain is changed to a greater degree withincreasing body mass gain as body mass is increased, due tothe decrease in protein accretion (Byers, 1980b; Meissner etal., 1982b; Rompala, et al., 1985).

Compensatory growth

The phenomenon of compensatory growth tends to assure thata certain carcass composition is achieved at a given mass.However, the relationship of protein deposition rate with bodymass and body mass gain, is modified by the extent ofcompensatory gain during compensation (Rompala et al.,1985). Studies have shown that cattle exhibiting compensatory



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FIGURE 1: Rate and composition of growth in medium frame weaner steers fed diets of different dietary energyconcentrations and feed intake levels (Slabbert & Campher, 1989 unpublished data)

growth with increased rates of gain compared to the controls,tend to be of similar body composition when slaughtered atmasses similar to that of the control animals (Winchester &Howe, 1955 as cited by Rompala et al., 1985; Fox et al., 1972;De Bruyn, 1983). In contrast, steers realimented afterrestricted feeding showing rates of gain similar to controls,were leaner than controls when slaughtered at similar masses(Lawrence & Pearce, 1964 and Tudor et al., 1980 as cited byRompala et al., 1985; Rompala et al., 1985). Fox et al.(1972), using small-frame steers and Rompala et al. (1985),using large-frame steers, found that gain contained less fatduring early compensation but more during later stages ofcompensation than gains of cattle not subjected to a feedrestriction period.

Nutritionally related interactions

At a given body mass and body mass gain early-maturingcattle showed a greater degree of change in composition whencompared with later-maturing cattle due to differences inphysiological maturity. This is also applicable to bulls vs steersvs heifers and implanted vs non-implanted animals. It appearsthat a reduction in energy intake has a more depressing effecton protein retention and growth rate than on lipid deposition inlarge mature animals and bulls, but a more depressive effecton lipid retention than on growth rate and protein retention inearly maturing animals and heifers (Robelin & Geay, 1983).The results of Ferrell & Jenkins (1985) also indicate that at adlibitum intakes lean tissue (water and protein) gain of a late

maturing breed were greater than that of an early maturingbreed and that this advantage de-20 years have centeredaround the growing and finishing of cattle. Feed cost, exceptcattle purchase cost, is the most expensive component offeedlot costs and if managed effectively contribute greatly tothe success of any feedlot operation (Ford, 1988). Theapplication of knowledge in the following nutritionally relatedareas should be considered during the process of integratedgrowth management to improve feed efficiency:

Protein

Results of Zinn (1986a) and Sip (1988) indicate that growthperformance of steers is not influenced by a relatively widespectrum of crude protein levels (90 to 120 % of NRC 1984recommendations) which indicate that requirements may besomewhat over estimated in certain production situations.Results of Merchen et al. (1987), however, show that a smallprotein deficiency of 1,5 percentage units lower than the NRC(1984) recommendations, depresses the growth rate and feedefficiency of weaner calves during the growth phase by 8 %and 6 % respectively. Data from Anderson et al. (1988) alsoindicate that the NRC (1984) equations predict the crudeprotein requirements of bulls reasonably well. From thisdiscussion the inaccuracies of the factorial approach inaccounting for variation in animal performance is clearlydemonstrated. The NRC (1984) indicated, however, that theirlisted minimum requirements should be sufficient for a givenclass of cattle (frame type, sex condition, mass) in 50 percent



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FIGURE 2: The effect of anabolic agents on modifying priorities for empty body protein and fat gain in steers vs rate ofgrowth (Lemieux et al., 1988)

of the cases. To calculate adequate requirements for cattle in84 percent of the cases, an additional 14 percent must beadded (NRC, 1984).

Additional protein may be economically justified to increaseanimal performance early in a feeding period, although cattlefed a lower protein diet will make compensatory gains later.Fox et al. (1972) suggested that a higher protein:energy ratio(P:E; g crude protein/MJ ME kg-1 DM) may be required duringcompensatory growth. Results of Mader et al. (1989) suggeststhat a 16 % higher protein to energy ratio than indicated by theNRC (1984), was needed during the early phase ofrealimentation to achieve optimum gains. Cattle managedunder beef production systems to develop and take advantageof their compensatory gain potential, will usually respond tohigher levels of protein than that recommended by the NRC(1984). A high-energy finishing diet must, however, be fedduring the realimentation period immediately after an extendedperiod of nutritional restriction and at least a portion of thesupplemental nitrogen must come from natural proteinsources. If the feedlot period involves feeding lower energydiets during the initial realimentation period, additional proteinis not warranted.

Dietary energy concentration

Concentrate to roughage ratio and feed intake level

In Figure 3 the effect of different combinations of energyconcentrations and/or feed intake levels on efficiency ofmetabolizable energy utilization (MJ ME/kg carcass gain) forweaner steers slaughtered at the same live mass, are shown(Slabbert & Campher, 1989, unpublished data). The increasein efficiency with an increase in the dietary energyconcentration is clearly demonstrated on the ad libitumtreatments of the 30:70; 55:45 and 80:20 concentrate toroughage ratio's. This is due to an increase in energy intake(less physical limitation) and metabolizibility (Meissner & Roux,1983) which is associated with an almost linear increase ingain. The efficiency response at sub ad libitum feed intakelevels on the 55:45 and 80:20 diets, varied from slightly betterto slightly less than ad libitum. For the 30:70 diet, however, amarked decrease in efficiency with sub ad libitum feed intakelevels were obtained. Dietary treatments which induce adeclining growth pattern (as obtained by a decreasing energyconcentration at ad libitum or a decreasing feed intake level ofa particular dietary concentration) tend to be less efficient thanthose with an accelerating growth pattern obtained with theinverse dietary treatments.

Although net energy equations (NRC, 1984) indicate thatefficiency of feed utilization will be greater when feed intake ishighest, several recent studies have challenged thisassumption. Results discussed by Meissner (1983b), Hicks et

al. (1987, 1988a), Plegge (1986b) and Zinn (1986b) show thatfeed efficiency of feedlot cattle can be improved by restrictingor controlling feed intake. A review of the research conductedon controlled feeding would suggest that yearlings respondmore favourably than weaner calves, as all the studies usingyearlings have shown that controlled feeding increases feedefficiency. All the studies which have shown reduced feedefficiency with controlled feeding have been with calvessuggesting that compensatory growth may be responsible forthe better efficiency of yearlings. Based on more recent data,Hicks et al. (1988a) concluded that the optimum level of feedrestriction for typical feedlot diets appears to be between 90and 95 % of ad libitum.

Optimizing partial digestibility of starch

Starch is the primary source of energy in feedlot diets. Cattleconsuming starch in cereal grains ferment a portion of thestarch in the rumen and a variable portion, depending onprocessing method and type of grain, escapes ruminalfermentation and passes to the small intestine for enzymaticdigestion (Table 2). The general concept of grain processingand feed efficiency as presented in Table 2 suggests thatmaximum ruminal digestion is ideal. Steam flaking of grain, forexample, increases the extent of ruminal digestion andincreases feed efficiency (feed/gain). However, a regressionrelationship (Owens et al., 1986) between gain to feed ratios,an index of efficiency, and extent of digestion of starch in therumen and small intestine, indicates that an increasing extentof digestion at both sites is important, but of the two sites,fermentation of starch in the rumen was only 70 % as valuableas digestion of starch in the small intestine.

However, the amount of starch digested in the small intestinerelative to that fermented in the rumen is small andincomplete; only 5 to 17 % of the total dietary starch and from47 to 88 % of the starch reaching the small intestine isdigested. Several researchers such as Orskov (1986)suggested that enzyme activity limits the extent of digestion ofdietary starch in the small intestine. However, a plot of starchdisappearance from the small intestine obtained with varioustypes of grains and processing methods resulting in variouslevels of starch flow to the small intestine of steers indicate alinear relationship (Owens et al., 1986). Furthermore, attemptsto increase intestinal pH with dietary buffers have neversucceeded and no research to date has proven amylaseactivity or pH to limit intestinal digestion of starch (Owens etal., 1986). For whole, rolled and ground maize and sorghumgrain, particle size, and thus the surface area available forenzymatic attack, limits the extent and rate of starch digestion.Since the smaller particles and soluble starch have alreadybeen fermented in the rumen, surviving starch is moreresistant to solubilization and digestion (Owens et al., 1986).This means that little starch reaching the small intestine is



24

found in particles less than 500 microns (Kim & Owens, 1985).On the other hand postruminal digestion of maize grainparticles greater than 1 mm in diameter is virtually zero (Kim &Owens, 1985). More of the starch from unprocessed grainescapes digestion in the rumen and passes to the smallintestine, but only fine particles are well digested in the smallintestine. To optimize escape without sacrificing digestion,processing to achieve a particle size between 500 and 1000microns may prove useful to maximize efficiency (Owens etal., 1986).

Research results summarized by Brethour (1985, 1986)indicate a curvilinear relationship between feed efficiency andparticle size ( Table 3). The feed efficiency of finely rolled grainsorghum was respectively 6,8 % and 8,3 % better thancoarsely rolled or finely ground grain sorghum. Grain can beover-processed because cattle performance has been erraticand generally poorer with too finely ground grain. Other factorswhich alter rate of digestion and/or residence time in the smallintestine such as source of roughage, feed intake level, buffersand ionophores, can also be important.

Compounds within the small intestine may inhibit starchdigestion. Mahmoudzadeh et al., (1985) found that varioustannin and lignin components show anti-amylase activity.Reconstitution (Reicert et al., 1980) and termo-ammoniation(Slabbert & Leeuw, 1990) decrease the tannin content whichimproves feed efficiency of high tannin grain sorghum diets.

Generally, the more extensive the processing, the greater theextent of digestion within the rumen (Table 4). The extent ofruminal digestion is usually considered to be the multiple of therate of fermentation and time available for fermentation.Different feed grains differ in their rates of fermentation andthe fermentation rate of a given grain is influenced by theextent of processing (Table 4). Generally, any grain typeand/or processing method that will increase the rate andamount of starch fermented in the rumen increases thepossibility of acidosis. Acidosis is one of the most importantnutritional disorders in feedlots and is associated with anincrease in the total VFA concentration and ruminal lactateconcentration (Burrin & Britten, 1986) resulting in a drop ofruminal pH. To prevent and reduce the incidence of acidosisthe amount and rate of starch fermented in the rumen must bemanipulated through the regulation of starch intake and/orgrain fermentation rate as well as the use of ionophores,buffers and roughages.

Feeding a mixture of rapidly digesting grains (wheat, barley,high moisture maize) and slowly digesting grains (grainsorghum, dry maize) may reduce the incidence of acidosis andimprove over-all starch utilization. The complementary effectsof feeding a combination of early harvested high moisturemaize (HMM) with dry maize (whole or rolled) (Stock et al.,1987a) and with dry rolled grain sorghum (DRGS) (Stock etal., 1987b) were demonstrated in beef cattle diets. Cattle fed acombination of 67 - 75 % of HMM with 33 - 25 % DRGS or dry



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FIGURE 3: Efficiency of energy utilizataion of weaner steers on various nutritional management programmes, slaughtered atthe same live mass (Slabbert & Campher, 1989 unpublished data)

maize, gained 2,7 % faster and 4,6 % more efficiently thanpredicted from the performance of cattle fed either of thegrains alone. The greatest improvement in animal performanceoccurred during the adaptation period. Results further indicatethat the slope of expected gain and feed/gain differ for DRGSand dry maize (Stock, 1988).

The efficiency of utilization of cereal grains in high-concentrate fattening diets is usually improved by grainprocessing. However, whole maize grain can be utilizedsatisfactorily by beef steers if given with a limited amount of, oreven no roughage (Nixon et al., 1969; Van Niekerk & Tarr,1982; Campher et al., 1983b; Slabbert et al., 1988). The useof whole maize grain in feedlot diets is not very popularbecause of the variable results which have been obtained.Some of the important factors which influence the intake anddigestion of whole grain are the type, amount and physicalform of the roughage (Cole et al., 1976; Campher & Hofmeyr,1986) and/or the physical properties of whole grain (Toland,1976; Campher & Hofmeyr, 1985). In a feedlot studycomparing the grain of a softer high lysine (HL2) cultivar withthat of a hard normal cultivar, steers fed HL2 had asignificantly (P<0,01) higher carcass gain and feed efficiency.With the increased cost of grain processing, it could beadvantageous to use whole maize grain rather than processedmaize in feedlot diets (Slabbert et al., 1988). In contrast withmaize grain, grain sorghum must be processed to be efficientlyused in beef cattle diets (Slabbert, 1987).

Roughage source

Roughages (either grazed or harvested forages, crop residuesor byproducts) may be the most economical source of energy,protein and other nutrients when high levels of animalperformance are not required. In mixed diets, roughage toconcentrate ratios can be manipulated to achieve dietaryenergy concentrations appropriate for various levels of animal

productivity. Roughages are included in higher concentratediets, not so much for the nutrients they contribute, as for theirrole in stimulating feed intake and maintaining a rumenenvironment which lessens the incidence of acidosis (Swingle,1987). Associative effects between roughages andconcentrates may be due to a reduction in starch degradationor to depressed cellulolysis (Mould, 1988). Depressed starchdigestibility is the major contributor in higher concentrate diets,while the latter is more important on lower concentrate diets.Lower quality roughages, such as cereal straws andcottonseed hulls, have a much higher feeding value in high-concentrate diets than in high-roughage diets. This appears tobe due to the superior ability of these roughages to maintainrumen pH in a more desirable range, probably by stimulatingrumination, and also by enhancing starch digestion byalteration of digesta passage rate and site of digestion (Owenset al., 1986; Swingle, 1987). Studies of Meissner et al. (1982a)and Campher et al. (1983a) also indicate that peak intake andretention time of ground maize meal is a function of the type ofroughage, its particle size and mass to volume ratio.

Feed additives

Antimicrobial growth promotors

Ionophores

No other group of compounds has had such an important andwide ranging economic impact on ruminant production underboth intensive and extensive management conditions as theionophores (Bergen & Bates, 1984; Schelling, 1984; VanNiekerk, 1987). The following major areas of animal



26

FastWheatBarleySteam flaked maize, high moisture maize (storewhole, fed whole)Dry rolled maize, reconstituted grain sorghum,steam flaked grain sorhumDry whole maizeDry rolled grain sorghum

Slow1 Stock (1988)

TABLE 2: Grains categorized by rate of starchbreakdown in the rumen1.

ITEM COARSELYROLLED

FINELYROLLED

FINELYGROUND

Relative feed intake 104,2 100,0 97,0Relative average daily gain 97,1 100,0 90,5Relative feed conversion ratio 93,8 100,0 95,2Range in particle diameter(microns) -

Parcticle size distribution (% of total mass)

2000 - 4000 36 17 01000 - 2000 52 64 14500 - 1000 6 13 53<500 6 6 35Approximate mean particlesize

2 mm 1 mm 0,5 mm

1 Adapted from Brethour (1985, 1986)

TABLE 3: Acomparison of coarsely rolled, finely rolled,and finely ground sorghum on feedlotperformance of steers (Pooled results of 20trails)1

metabolism contribute to, or account for the noted animalperformance enhancement due to the selective inhibition ofrumen micro-organisms and coccidia by ionophores:

Health related benefits

The use of ionophores may dramatically reduce the incidenceof lactic acidosis and grain bloat which is the two mostimportant practical problems experienced during the use ofhigh energy feedlot diets. The inclusion of ionophores makethe use of concentrated diets far safer without the need forelaborate adaptation procedures (Van Niekerk, 1987). Theeffectiveness of the ionophores monensin and lasalocid inreducing the severity of acidosis is due to their inhibitory effecton the predominant lactate producing rumen bacteria (Denniset al., 1981; Bartley & Nagaraja, 1982). Both lasalocid andmonensin have been shown to be effective in preventing invivo feedlot bloat (Bartley et al., 1983), by a bactericidal effecton gram positive ruminal lactic acid producers, an anti-protozoal effect (Bergen, 1984) and a decrease in rumen fluidviscosity (Bergen & Bates, 1984). Ionophores can also controlcoccidiosis (Horton, 1982) and reduce the incidence oflaminitis (Van Niekerk, 1987).

Utilization of protein

Ionophores usually improve nitrogen metabolism in the rumenand/or animal. This is associated with a decrease in theruminal degradation of the dietary protein and amino acids bymonensin (Schelling et al., 1977), a decline in rumenammonia-nitrogen (Chalupa, 1980, Schelling, 1984), as well asa decrease in microbial protein synthesis by both monensinand lasalocid (Bartley & Nagaraja, 1982). The nett effect ofionophores is to reduce microbial protein reaching theabomasum while allowing more undegraded feed protein tobypass the rumen (Poos et al., 1979; Short et al., 1978; Zinn,1987a), which may increase both the quantity and/or quality ofprotein reaching the lower gastro-intestinal tract for digestionand absorption.

Improved feed efficiency

One of the primary reasons for the widespread use ofionophores in feedlot diets is the consistent markedimprovement in the efficiency of feed conversion resulting fromtheir use (Table 5). Generally, when diets containing highlevels of readily fermentable carbohydrates are fed, feedintakes are depressed while gains are maintained, therebyimproving feed conversion (feed/gain). This improvement isattributed to the increased efficiency of energy metabolism inthe rumen and/or animal which is related to a shift in ruminal



27

GRAIN AND PROCESSINGMETHOD

STARCH DIGESTIBILITYRumen Small intestines Large intestines Total tract Small intestines Large intestines Post ruminal Grain/gain2

% of starch in diet % of starch inputMAIZE

Whole 58,9 17,0 2,8 91,7 66,9 33,3 75,4 6,85Cracked 68,9 12,9 8,2 87,6 46,7 55,5 69,9Rolled 71,8 16,1 4,9 93,2 53,7 37,2 73,1 6,90Ground 77,7 13,7 4,3 93,5 56,3 37,0 66,8Ensiled 86,0 5,5 1,0 94,6 76,4 55,0 89,8 6,45Steam flaked 82,8 15,6 1,3 97,8 88,1 61,9 87,9 6,33

SORGHUMRolled 67,8 13,4 5,9 86,4 37,8 33,3 54,8 7,30Ensiled 86,2 9,5 1,1 93,6 69,2 29,5 78,1 6,29

1 Modified from Owens et al., 1986. Total tract digestibility does not necessarily equal the sum of digestion at individual sites because site of digestion was notmeasured in all trails2 From Hale and Prouty, 1980a Modified from Owens et al., 1986. Total tract digestibility does not necessarily equal the sum of digestion at individual sites because site of digestion wasnotmeasured in all trailsb From Hale and Prouty, 1980

TABLE 4: Recent measurements of site and extent of starch digestion with maize and sorghum grains processed byvarious methods1.

propionate production and a concomitant decline in acetateand methane production (Bergen, 1984). It is however obviousthat the improved energy efficiency together with other areasalready discussed (reduced incidence of bloat, acidosis andcoccidiosis as well as more efficient protein utilization)contribute to the overall improvement in efficiency. Recent dataindicating the ability of ionophores to alter the absorption andretention of minerals as well as to modify the availability ofnon-mineral and mineral nutrients to the animal cells suggeststhat these metabolic changes may contrib-ordinated with eachionophore fed to maximize their effect.

The use of ionophores under veld or pasture grazingconditions are not common and their potential application areneglected by researchers in this country. The results ofoverseas studies are variable, but generally show fairly markedpositive responses when monensin or lasalocid are fed onpastures or with high roughage diets (Van Niekerk, 1987). Onhigh roughage diets feed intakes are usually not depressedbut gains are generally increased which improve feedconversion (Bergen & Bates, 1984). However, there appearsto be an interaction between the intake response due toionophore supplementation and forage digestibility. Monensindepresses intake and thus animal performance on lessdigestible (45 %) forages (Ellis et al., 1988), while enhancingintake on forages with an intermediate digestibility. Ionophores(monensin in particular) are unpalatable and it is necessary touse palatable carriers to achieve the required ionophoreintake. The development of a ruminal delivery device, showspromise as a method of supplying monensin to grazing cattle(Davenport et al., 1989).

Recent pooled research results of 5 trials (Johnson, 1987)demonstrated that the rotation of ionophores (lasalocid witheither monensin alone or monensin plus non--ionophoreantibiotic tylosin), tend to improve gain and feed efficiency asopposed to either of the ionophores fed alone (Table 6).Ionophore rotation is based on the theory that there ismicrobial adaptation to ionophores and/or possible subtledifferences in their metabolic effects (Galyean & Owens,1987). In spite of inconsistencies in reported results (Johnson,1987; Galyean & Owens, 1987; Hicks et al., 1988b; Branine etal., 1989), results suggest that daily ionophore rotationprogrammes may optimize the benefits from ionophores.

Antibiotics

Antibiotics are primarily fed to finishing cattle for the control ofliver abscesses which results from feeding high energy dietsover extended periods. In a survey of experiments, Brink(1985) found that steers with several abscessed (A+) liversgained 11,5 % slower, consumed 3,9 % less feed and required9,7 % more feed per unit gain than steers with non--abscessed livers. Acidosis which is associated with the use of

high energy diets may damage the rumen wall causing micro--organisms to penetrate the gut wall from where they aretransported by the blood to the liver where abscesses areformed. The beef producers in South Africa are not directlypenalised for marketing abscessed livers. Probably for thisreason and because of the shorter feeding periods used, beefproducers are not particularly concerned about the preventionof liver abscesses (Van Niekerk, 1987). The use of feedadditives such as ionophores and other antibiotics as well asbuffers in high grain diets which help to prevent and reducethe severity of acidosis can be expected to contribute to thereduction of liver abscesses. Antibiotics have been shown toimprove gain and feed efficiency, but this response may beprimarily due to the reduction of liver abscesses. Commonlyused non--ionophore antibiotics such as zinc bacitracin andflavomycin, which act largely within the digestive track, cannotbe as effective as those antibiotics which can also act directlyupon the liver (Van Niekerk, 1987) such as tylosin.Combination feeding of ionophores and one or more non-ionophore antibiotics in feedlot diets has proven beneficial andis widely used.

Scheduled antibiotics such as tetracyclines, are increasinglybeing used as routine feed additives either in starter diets orthroughout the fattening period, as they reduce losses due torespiratory and other diseases (Van Niekerk, 1987).

The use of non-ionophore antibiotics, such as flavomycin andavoparcin, under veld and pasture grazing conditions areneglected. Results discussed by MacGregor (1988) indicatethat the inclusion of avoparcin in supplements to grazing cattleimproved daily gain from 9,6 to 11,6 %.

Vitamins

Under most circumstances vitamin deficiencies of grazingruminants should not be a major problem due to synthesis ofthe B-vitamins, vitamin D and vitamin K. Supplemental vitaminA and E are, however, required. In principle the same holdstrue for the fat-soluble vitamins in feedlot cattle. Due todifferent feeding practices, however, feedlot cattle may alsorequire vitamin B1 (thiamine) and niacin (Fröhli, 1987). Cattle



28

IONOPHORE AVG. DAILY GAIN2 FEED: GAINMonensin 96-100 88-95Lasalocid 99-107 90-96Narasin 87-100 84-90Salinomycin 102-106 931 Results are summaries across all types of diets (Owens, 1980); Ionophoreswere fed in the effective range to feedlot cattle2 All masses adjusted for 4 % shrinkage

TABLE 5: The effect of ionophores on performance offeedlot cattle1.

fed supplemental vitamin E (Adams & Zimmerman, 1984) andniacin (Robinson, 1986) showed improved mass gain and feedefficiency. Niacin supplementation benefits the adaptation ofcattle to feedlot diets (Robinson, 1986). The recommendedsupplemental vitamin levels for feedlot cattle according toFröhli (1987) are 40 000 - 60 000 IU/animal/day for vitamin A,100 - 200 mg/animal/day for vitamin E, 20 - 30 mg/animal/dayfor vitamin B1 and 1000 - 1500 mg/animal/day for niacin.

Buffers

The animal's need for buffers occurs primarily in situationswhere high concentrate diets are being fed or where themineral balance of the diet is not appropriate. In highconcentrate diets the need probably occurs because there isless chewing and regurgitation, in turn, causes less saliva anda reduced amount of bicarbonate coming into the rumen toprevent a decrease in rumen pH. Buffers may be usedespecially during the adaption process to high concentratediets. Calcium bicarbonate can increase starch disappearancein the small intestine on low calcium diets, without increasingthe ileal pH (Goetsch, et al., 1985). Concentrations of calciumup to 0,70 % of the diet often increase starch digestibility(Owens et al., 1986).

Nutritional management of newly arrived

feeder cattle

Newly received feeder calves or yearlings coming from a widevariety of production systems, and suffering from stresses ofweaning or inadequate nutrition, marketing and transportationmay be subjected to varying degrees of growth restrictioncaused by processing and handling procedures, disease leveland nutrition regimes during the critical first 4 weeks afterarrival (Lofgreen, 1983, as cited by Lofgreen & Kiesling, 1985).

Of utmost importance are diets that will be consumed andfurnish the essential nutrients. However, the appetite (orwillingness to eat) of newly arrived feeder cattle is low duringthe first weeks after arrival (Table 7) (Hutcheson, 1989a). Highenergy receiving diets consistently improved feed intake ofstressed calves. Results of Lofgreen & Kiesling (1985) clearlydemonstrate that calves fed a 75 % concentrate receiving dietplus hay limited to the first week only, ate more feed, gainedmore mass and required less feed per unit of gain (P<0,01),than those received on hay alone plus a 40 % proteinsupplement. Calves fed hay plus a protein supplement atemore feed, gained more mass and required less feed per unitgain than those fed hay alone. Nutrient specifications for newlyreceived calves are shown in Table 8.

Cattle subjected to the stresses of marketing and transportencounter many metabolic changes, one of which is live mass



29

VARIABLE TREATMENT 0-28 DAYS S0-56 DAYS 0-FINALDry matter intake (kg/day) Lasalocid 20,14a 21,14a 21,36ac

Monensin/tylosin 19,83a 20,38b 20,86b

Daily rotation 19,84a 20,84ab 21,45c

Weekly rotation 19,66a 20,49b 21,00bc

Bi-weekly rotation 19,54a 20,19b 20,71b

Average daily gain, carcass1 (kg/day) Lasalocid 3,87ab

Monensin/tylosin 3,80a

Daily rotation 3,99b

Weekly rotation 3,86ab

Bi-weekly rotation 3,87ab

Feed/gain, carcass (kg/day) Lasalocid 5,59a

Monensin/tylosin 5,55a

Daily rotation 5,43a

Weekly rotation 5,48a

Bi-weekly rotation 5,42aa,b,c Means in a column with different alphabetic superscripts differ, P<0,051 Adjusted masses calculated to constant dressing percentage of 63 %

TABLE 6: Ionophore rotation: Pooled analysis of 5 studies: Adjusted means for dry matter intake, average daily gain andfeed/gain (Johnson, 1987).

loss primarily due to dehydration caused by body and digestivetract water losses (defaecation and urinary loss). Duringdehydration or shrink, water is lost from within the cells of thebody and cellular deficiency of potassium (K) and sodium (Na)can occur. Results of Hutcheson et al. (1984) suggests thatadditional K to provide 1,2 to 1,4 % K in the diet for the firsttwo weeks is the most optimum level, based on mass gain, fornewly received calves fed hay pre-transport (Table 8).Hutcheson et al. (1984) observed a significant interactionamong the pre- and post-transport dietary treatments and Klevel for mass gain, as calves that had been fed a 55 %concentrate diet for 3 days pre-transport, did not show a massgain response to the 1,3 % K level. According to Hutcheson(1989a), additional K will give the largest response in thosecattle which have shrunk the most. If cattle shrink 2 to 4percent, additional K may not result in a gain response, butwith 7 or more percent shrinkage, a significant effect can beobserved when additional K is added. Potassium level had nosignificant effect on morbidity (Hutcheson et al., 1984) butadditional K significantly reduce mortalities and increasesaverage daily gain and feed efficiency (Hutcheson, 1989a).

In recent years it has been demonstrated that deficiencies intrace minerals; zinc (Zn), copper (Cu), selenium (Se), iron (Fe)and heavy metals impaired immunocompetence (Hutcheson,1989b). Trace mineral deficiencies and excesses can affectthe immune system, but specific levels and action have notbeen completely documented. However, based on literatureand research, Hutcheson (1989b) recommended the levels oftrace minerals listed in Table 8 for newly received stressedfeeder calves. These levels should be adequate for cattleconsuming 1,0 to 1,5 % of their body mass as dry matter.

The computer as management aid

The computer can be a successful management aid in thedecision making process, ranging from record keeping, dataevaluation, diet formulation, estimation of nutrientrequirements, feed intake and growth rate, to economicprojections. Accurate economic projections are dependent onaccurate predictions of performance, which in turn isdependent on the ability to describe and account for thevariables that influence requirements of cattle. The NRC(1984) nutrient recommendations for beef cattle haveinsufficient adjustments for variations in biological type andassume that cattle are fed in a no-stress environment. Theserequirements, determined under standardized conditions, areapplied indiscriminately to an infinite combination of breedand/or frame types, management and environmentalconditions. Fox et al., (1988) developed models to adjust thesenutrient requirements of growing beef cattle and beef cows forenvironmental variations and cattle types.

Several models (NRC, 1984; Fox & Black, 1984; Oltjen et al.,1986a as cited by Fox et al., 1988) appear to predict gainswith similar accuracy and in validation tests under commercialfeedlot conditions predictions within 1 to 5 % of actual gains(Fox et al., 1988) were obtained. The Oltjen model based onpredicting daily DNA and protein synthesis for a given maturesize and feeding system, however, has the highest precision insimulating body mass gain and composition (Fox et al., 1988).The addition of an environmental submodel and the use ofmore descriptive input data on animal and environmentalconditions can make this model an useful aid in evaluatingdifferent feed management strategies. Advances in non-linearprogramming now allow a method for optimally planning afeeding programme based on optimal-return-diets and least-cost-gain diets (Hertzler et al., 1988).

NUTRITIONAL STRATEGIES FOR GROWTH

MANIPULATION

The objective of growth management, within a specificproduction system, is to regulate growth and synchronizenutrient supplies with nutrient needs to support the desiredtype of growth, and/or to reach an optimum carcasscomposition at a specific slaughter date. This can beaccomplished through both endogenous mechanisms inherentto an animal i.e. castration, or through exogenous mechanismssuch as with anabolic repartitioning agents. The concept thatcarcass tissues (bone, muscle and fat) reach their maximumgrowth rate at different stages of maturity (Berg & Butterfield,1976; Elsley, 1976) together with the concept that growth rateinfluences the composition of the carcass (Byers, 1980a,1982a; Meissner, 1983b; Rompala et al., 1985; Lemieux et al.,1988), create the opportunity to apply various nutritional(energy) strategies for growth manipulation. Nutritionalconsiderations which should be used in growth managementstrategies (Byers & Schelling, 1986) include:



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ITEM HEALTHY CALVES MORBID CALVESFeed intake (% of bodymass)

1 - 7 Days 1,55 (0,51)1 0,90 (0,75)1 - 28 Days 2,71 (0,50) 1,84 (0,66)1 - 56 Days 3,03 (0,43) 2,68 (0,68)

Daily gain (kg/day)1 - 7 Days -0,95 (1,14)a -2,85 (1,32)1 - 28 Days 0,59 (0,40) 0,009 (0,59)1 - 56 Days 0,91 (0,14) 0,64 (0,18)

1 Standard deviation

TABLE 7: Feed intake and daily gain of newly arrivedfeeder calves (Hutcheson, 1989a)

a) The stage of growth vs nutritional schedule- Growing vs fattening stage.- Current vs earlier nutritional history (compensation).- Deferred vs advanced systems, and

b) Dietary energy concentration and feed intake level- Forage vs grain.- Restricted feeding in accordance to limits for lean tissuegrowth.

- Rate and composition of growth.- Substrates for tissue growth.

Nutrition is normally considered in relation to a specific phaseof growth such as preweaning, growing or finishing anddifferent ranges of nutritional levels are implied in each phase.However, the general relationship of rate to composition ofgrowth applies to all phases of growth; only the relativepriorities for protein vs fat deposition change with stage ofgrowth. Beef cattle feeding and management systems includea range of nutritional programmes including periods of rapid

and periods of deferred growth. All periods of deferred, butpositive growth, result in the restriction of fat deposition. Thisresults in an older animal, thus having more time to depositprotein and thus to accumulate more lean (muscle) tissue. Fig.4 (Slabbert & Campher 1989, unpublished data) indicates towhat extent implanted medium frame weaner steers whichwere managed to grow continuously at different rates, canchange terminal carcass mass to obtain a constant carcassfatness of 18 %. Different growth rates were achieved byvarying the metabolizable energy intake through differentdietary energy concentrations and/or feed intake levels.Nutritional programmes designed to optimize lean tissuegrowth during the growing and finishing phases can thus helpto prevent that the need for leaner beef is associated with theproduction of a lighter carcass. However, the application ofdeferred feeding strategies to produce a high quality supercarcass can be constrained by the age classes in the gradingsystem. Age is determined according to the number ofpermanent incisors (p.i.) counted prior to dressing the carcass.Carcasses are grouped into three age groups, namely A-agegroup (0 p.i.); B-age group (1-6 p.i.) and C-age group (morethan 6 p.i.).

Systems of deferred feeding include growing weaned calveson several alternative nutritional systems:

1. Using all-forage diets throughout the growing and finishingperiod with or without limited amounts of concentrate.

2. Using all-forage diets (pasture) throughout the growing pe-riod with or without limited amounts of concentrate.

3. Increasing the amount of roughage in mixed concentrate-roughage feedlot diets.

4. Restricting feed intake on mixed concentrate-roughagefeedlot diets.

5. Increasing the length of the growing phase on all-forage,high-roughage mixed diets or restricted concentrate-roughage mixed diets and shortening the length of thefeedlot phase on high-concentrate diets.

The duration of the period to grow weaned calves inalternatives 2 to 5 to yearling masses or masses preferred byfeedlots, depends on the average daily gains and/or theplanned slaughter date. These practices give greater flexibilityof marketing date with regard to the availability of weanercalves and seasonal price cycles. These cattle will be leaner atany slaughter mass than cattle fed to grow rapidly immediatelyafter weaning. Growing cattle on alternatives 1 and 2, shouldconsume the maximum possible amount of forage plus enoughsupplement to achieve management objectives in terms ofanimal mass and condition at some predetermined time. The



31

NUTRIENT SUGGESTED RANGEFOR RECEIVING DIET

TAES RECEIVING DIET

Dry matter % 80 - 85 88Crude Protein % 12,5 - 14,51 13,9Net Energy of Mainte-nance (MJ ME/kg)

6,4 - 6,9 6,6

Net Energy of Gain (MJME/kg)

3,4 - 3,7 3,6

Calcium % 0,6 - 0,8 0,7Phosphorus % 0,4 - 0,6 0,5Potassium % 1,2 - 1,41 1,3Magnesium % 0,2 - 0,31 0,3Sodium % 0,2 - 0,3 0,3Copper, ppm 10 - 15 15,7Iron, ppm 100 - 200 210,7Manganese, ppm 20 - 30 26,3Zinc, ppm 75 - 100 81,7Cobalt, ppm 0,1 - 0,2 0,15Selenium, ppm 0,1 - 0,2a 0,15Vitamin A, IU/kg 4400 - 66000Vitamin E, IU/hd/daya 50 - 1001 Research at the TAES beef cattle facility has verified these nutrients, othersare calculated

TABLE 8: Nutrient recommendation for receiving calves(Hutcheson, 1989a).

amount and composition of the supplement required isdetermined by animal gain and grade potential, quantity andquality of forage available, and interactions among thesefactors.

One of the major problems is the relative short time and massinterval during which an animal maintains a specific gradewhen approaching slaughter mass. Extending this intervalwould provide more flexibility in marketing. This can beachieved by inhibiting growth of the undesirable fat componentduring its most dynamic phase of growth and/or optimizinglean tissue growth through rate of growth during all stages ofgrowth. A high compensatory growth rate in the finishingphase as obtained on typical high energy feedlot dietsfollowing a deferred feeding period can, however, decreasethe time and mass interval during which cattle maintain aspecific grade due to the higher fat content of the gain. Theonly way of avoiding excessive fat deposition by nutritionalmeans is to reduce the dietary energy concentration and/orfeed intake level and thus the growth rate during the latefinishing phase. Such a decelerating growth pattern can,however, cause a decrease in the overall feed conversion ratiodue to a higher maintenance component.

Net energy equations predict rate and efficiency of gainsatisfactorily over a feeding period (Oltjen & Garrett, 1988;Zinn, 1987b, 1989), and programming feed intake to attain aspecific growth rate would be the simplest method to applyrestricted feeding of concentrate diets under feedlot conditions.This will require reasonable estimates of the limits of differentbreeds or cattle types for rate of gain and voluntary intake.Depending on the dose response curve for ionophores, achange in their dietary concentration can be used tomanipulate feed intake and/or rate of gain. Further advantagesand possible limitations of restricted feeding of highconcentrate diets is discussed by Zinn (1989) and Slabbert(1990).

The nutritional interaction with frame type, sex and growthpromotor as discussed, supports the contention that smallerbreeds of cattle and heifers are more suited for feedingsystems that utilize diets with low energy density (Byers1982a, 1982b; Rompala et al., 1985; Meaker, 1988) on a timeconstant basis. Cattle of large genotypes or bulls fed foragediets, summer veld grazing or pastures may not finish atreasonable masses or within an economical length of time withan acceptable fatness and/or age class, because most of thedietary energy consumed would be utilized for maintenanceand lean growth. This indicates the application of deferredfeeding programmes for smaller mature size cattle or heifersand high energy feedlot programmes for large mature sizecattle and bulls. The choice of maturity type, however, is moreof an economic consideration; for instance, the feeder calf type(frame size) favoured by the feedlot industry is determined by

the price margin to feed margin ratio. Although theeffectiveness of anabolic growth promotors increases with rateof growth, their use from birth to slaughter, even undersystems of deferred feeding, provides lifetime growthregulation and maximal redirection of nutrients from fat toprotein and lean tissue production.

Nutritional practices during the first few weeks after feedercattle arrive at feedlots can have a major influence onsubsequent performance and health of cattle (Hutcheson etal., 1984). The nutritional needs of these cattle variedaccording to the stresses that had been imposed. Therefore,different diets and management systems may be required fordifferent groups of cattle. Starting cattle smoothly and quicklyon high concentrate diets, decreases the cost of production(Hutcheson, 1989a). Creep feeding and the timing of weaning,vaccination, castration and dehorning significantly affected theanimal's growth rate before and after entering the feedlot(Peterson et al, 1989)

Rate and efficiency of lean tissue growth are criticalcomponents in enhancing lean beef production through cattlefeeding and management systems. Nutritional strategiesenhancing lean deposition, unfortunately have certainlimitations such as the availability and price of forage and feedgrain, the feed grain to beef price ratio and the length of timerequired for the animal to reach slaughter mass. As profitmargins in the beef industry are generally small, nutritionalmanagement must be integrated in each production system tobe successful. This process must consider the availablebreed/type, sex, stage of growth and growth promotors tosystematically develop growth management programmes tooptimize beef production. Other factors, such as beef pricecycles and the availability of weaner calves must also be takeninto account.

SUMMARY

The need to produce beef carcasses that will fit consumerdemands is clear. Nutritional strategies can be designed to aidin lean deposition. Nutritional level under conditions of proteinadequacy, either through roughage to grain ratio and/or intakelevel, influences the composition of growth primarily through anaccelerated rate of growth above priorities of protein growth,so that the fat fraction increases with rate of growth. Methodsto optimize partial digestibility and the efficiency of feedadditives, and to improved nutritional management of newlyreceived feeder cattle, must be considered to increase feedefficiency on high energy feedlot diets. Rate and efficiency oflean tissue growth are critical components in enhancing leanbeef production through cattle feeding and managementsystems. Nutritional strategies unfortunately have certainlimitations such as the availability and price of forage and feedgrain, the feed grain to beef price ratio and the length of time



32

required for the animal to reach slaughter mass. As profitmargins in beef production are generally small, nutritionalmanagement to be successful must be integrated in eachproduction system. This process must take into account theavailable environmentally adapted breed/type, sex condition,stage of growth and growth promotors to systematicallydevelop growth management programmes to optimize beefproduction. Other factors, such as market trends in beef pricesand the availability of weaner calves must also be taken intoaccount.

REFERENCES

ADAMS, C.R. & ZIMMERMAN, C.R., 1984. Update onsupplemental vitamin E in beef cattle rations. Feedstuffs, 4June.

ABDALLA, H.O., FOX, D.G. & THONNEY, M.L., 1988.Compensatory gain by Holstein calves after underfeedingprotein. J. Anim. Sci. 66, 2687.

ANDERSEN, H.R., 1978. Effect of energy level on growth andefficiency. In: Patterns of growth and development in cattle.Eds. H. de Boer & J. Martin. Martinus Nijhoff, The Hague.CEC. p 393.

ANDERSEN, H.R. & INGVARTSEN, K.L., 1984. The influenceof energy level, weight at slaughter and castration ongrowth and feed efficiency in cattle. Livest. Prod. Sci. 11,559.

ANDERSON, P.T., BERGEN, W.G., MERKEL, R.A. &HAWKENS, D.R., 1988. The effect of dietary crude protein

level on rate, efficiency and composition of gain of growingbeef bulls. J. Anim. Sci. 66, 1990.

BARTLEY, E.E. & NAGARAJA, T.G., 1982. Lasalocid: Mode ofaction in rumen metabolism. In: Bovatec Symp. Proc. Eds.R.L. Stuart & C.R. Zimmerman, Hoffman - La Roche Inc.,Nutley, N.J. p 4.

BARTLEY, E.E., NAGARAJA, T.G., PRESSMAN., E.S.,DAYTON, A.D., KATZ, M.P. & FINA, L.R., 1983. Effects oflasalocid or monensin on legume or grain feedlot bloat. J.Anim. Sci. 56, 1400.

BÉRANGER, C., 1978. Feed efficiency and genotype-nutritioninteraction in growing animals, particularly in cattle for beefproduction. In: Patterns of growth and development inCattle. Eds. H. de Boer & J. Martin. Martinus Nijhoff, TheHague. CEC. p 383.

BERG, R.T. & BUTTERFIELD, R.M., 1976. New concepts ofcattle growth. Sydney University press. University ofSydney. Letchworth, England.

BERGEN, G.B., 1984. Ionophores - Mode of action and role inbeef cattle production. Animal Nutr. Conf. Proc. 19thAnnual Pacific Northwest, p 111.

BERGEN, W.G. & BATES, D.B., 1984. Ionophores: Their effecton production efficiency and mode of action. J. Anim. Sci.58, 1465.

BLACK, J.L. & GRIFFITHS, D.A., 1975. Effects of live weightand energy intake on nitrogen balance and total Nrequirements of lambs. Br. J. Nutr. 33, 399-413.



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FIGURE 4: The estimated final carcass mass of medium frame weaner steers at a constant carcass fatness of 18 % due todivergent dietary energy concentrations and feed intake levels (Slabbert & Campher, 1989 unp

BOND, J., HOOVEN, N.W., WARICK, E.J., HINER, R.L. &RICHARDSON, G.V., 1972. Influence of breed and planeof nutrition on performance of dairy, dual purpose and beefsteers. II. From 180 days of age to slaughter. J. Anim. Sci.34, 1046.

BRANINE, M. E., LOFGREEN, G.P., GALYEAN, M.L.,HUBERT, M.E., GARCIA, D.R. & FREEMAN, A.S., 1989.Dai ly ionophore rotat ion improves feedlot catt leperformance. Feedstuffs, April 24, p 18.

BRETHOUR, J.R., 1985. Rolling and grinding milo for beefcattle. Report of progress 475. Roundup 72. Kansas StateUniversity, p 6.

BRETHOUR, J.R., 1986. Advancing sorghum to its fullpotential in beef cattle rations. Grain Sorghum Conference,February, Dallas, Texas.

BRINK, D.R., 1985. Elanco: Liver abscess. Technicalinformation No. 7/85. p 16.

BURRIN, D.G. & BRITTON, R.A., 1986. Response tomonensin in cattle during subactute acidosis. J. Anim. Sci.63, 888.

BYERS, F.M., 1980a. Effects of limestone, monensin andfeeding level on corn silage net energy value andcomposition of growth in cattle. J. Anim. Sci. 50, 1127.

BYERS, F.M., 1980b. Systems of beef cattle feeding andmanagement to regulate composition of growth to producebeef carcasses of desired composition. Beef cattle nutritionand growth. A summary of Research. Ohio Agri. Resh. andDevelopment Center, South Wooster, Ohio.

BYERS, F.M., 1982a. Protein growth and turnover in cattle:Systems for measurements and biological limits. In:Protein Requirements of Cattle. Ed. F.N. Owens. Divisionof Agriculture, Oklahoma State Univ. MP - 101, 141.

BYERS, F.M., 1982b. Nutritional factors affecting growth ofmuscle and adipose tissue in ruminants. Fed. Proc. 41,2562.

BYERS, F.M. & ROMPALA, R.E., 1980. Level of energy effectson patterns and energetic efficiency of tissue deposition insmall or large mature size beef cattle. In: EnergyMetabolism. Ed. L.E. Mount. Eur. Assoc. Anim. Prod. Pub.No. 26. Butterworth's Scientific Pub., London. p 141.

BYERS, F.M. & SCHELLING, G.T., 1986. Integratedmanagement for production of beef lean. SyntexSymposium. Producing Safe Wholesome Beef. October1986.

CAMPBELL, R.G., 1988. Nutritional constraints to lean tissueaccretion in farm animals. Nutr. Res. Rev. 1, 233-253.

CAMPHER, J.P., ROUX, C.Z. & MEISSNER, H.H., 1983.Influence of roughages on rumen retention time ofconcentrates. S. Afr. J. Anim. Sci. 13, 48.

CAMPHER, J.P. & HOFMEYR, H.S., 1985. The influence ofgrain softness on the digestibility of whole maize graindiets. Short paper delivered at the 24th Congress of theSouth African Society of Animal Production, 2 - 4 April,Stellenbosch (unpublished).

CAMPHER, J.P. & HOFMEYR, H.S. 1986. The influence ofroughage on digestibility of whole maize grain diets. S. Afr.J. Anim. Sci. 16, 54-56.

CAMPHER, J.P., SHELBY, T., MEISSNER, H.H. & JANSE VANRENSBURG, N., 1983. Whole maize versus ground maizein fattening diets for beef steers. S. Afr. J. Anim. Sci. 13,262-264.

CHALUPA, W., 1980. Chemical control of rumen microbialmetabolism. In: Digestive Physiology and Metabolism inRuminants. Eds. Y. Ruckelbush & P. Thivend. Avi.Publishing Company, Inc., Westport, CN. p 325.

COLE, N.A., JOHNSON, R.R. & OWENS, F.N., 1976.Influence of roughage level on the site and extent ofdigestion of whole shelled corn by beef steers. J. Anim.Sci. 43, 483-489.

DAVENPORT, R.W., GALYEAN, M.L., BRANINE, M.E., &HUBBERT, M.E., 1989. Effects of a Monensin ruminaldelivery device on daily gain, forage intake and ruminalfermentation of steers grazing irrigated winter wheatpasture. J. Anim. Sci. 67, 2129.

DE BRUYN, J.F. , 1983. Kompensator iese groei enweefselsamestelling by vleisbeeste. MSc (Agric) Thesis.Univ. Pretoria.

DE BRUYN, J.F., GALLOWAY, M. & NAUDÉ, R.T., 1984.Growth hormone trail with steers. Revalor symposium -Field trials in Southern Africa.

DENNIS, S.M., NAGARAJA, T.G. & BARTLEY, E.E., 1981.Effect of lasalocid or monensin on lactate - producing orusing rumen bacteria. J. Anim. Sci. 52, 418.

ELLIS, W.C., WYLIE, M.J. & MATIS, J.H., 1988. Dietary-digestive interactions determining the feeding value offorages and roughages. In: World Animal Science B4. Ed.Orskov, E.R. Feed Science. Elsevier Science Publishers. p177.



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ELSLEY, F.W.H., 1976. Limitations to the manipulation ofgrowth. Proc. Nutr. Soc. 35, 323.

FERRELL, C.L. & JENKINS, T.G., 1985. Energy utilization byHereford and Simmental males and females. Anim Prod.41, 53.

FORD, D., 1988. The feedlot industry in perspective. SASAPCongress, Bloemfontein, South Africa.

FOX, D.G., JOHNSON, R.R., PRESTON, R.L., DOCKERTY,T.R. & KLOSTERMAN, E.W., 1972. Protein and energyutilization during compensatory growth in beef cattle. J.Anim. Sci. 34, 310.

FOX, D.G. & BLACK, J.R., 1984. A system for predicting bodycomposition and performance of growing cattle. J. Anim.Sci. 58, 725.

FOX, D.G., SNIFFEN, C.J. & O'CONNOR, J.D., 1988.Adjusting nutrient requirements of beef cattle for animaland environmental variations. J. Anim. Sci. 66, 1475.

FRÖHLI, D.M., 1987. The importance of the vitamins A, E, B1and niacin in beef cattle diets. F. Hoffmann-La Roche &Co. Ltd., Basel.

GARRETT, W.N., 1978. Protein production by growingruminants as influenced by dietary nitrogen and energy. In:Prod. Publ. No. 22. Ed. S. Tamminga. Wageningen.Netherlands. pp 115-118

GARRETT, W.N., 1980. Factors influencing energetic efficiencyof beef production J. Anim. Sci. 51, 1434.

GALYEAN, M.L. & HUBBERT, M.E., 1989. Ionophoreselection, use dependent on various factors. Feedstuffs,May 8, 1989. p 22.

GALYEAN, M.L. & OWENS, F.W., 1987. Ionophore rotationprograms: possible mechanism(s) of action. RocheIonophore Rotation Program Symposium.

GALYEAN, M.L., WAGNER, D.G. & OWENS, F.N. 1981. Drymatter and starch disappearance of corn and sorghum asinfluenced by particle size and processing. J. Dairy Sci. 64,1804.

GEAY, Y. & ROBELIN, J., 1979. Variation of meat productioncapacity in cattle due to genotype and level of feeding:Genotype - nutrition interaction. Livest. Prod. Sci. 6, 263.

GOETSCH, A.L., OWENS, F.N. & BROWN, B.E., 1985.Calcium level and source and digestion of highconcentrate diets by steers. J. Anim. Sci. 61, 995.

GRAINER, R.B., BATES, D.B. & GREENE, L.W., 1989.Ionophore/mineral interrelationships in ruminantsexamined. Feedstuffs, February 13, p 14.

HALE, W.H. & PROUTY, F.L., 1980. Grain processing systemsfor milo and corn. Univ. Arizona Cattle Feeder's Day Rep.

HERTZLER, G., WILSON, D.E., LOY, D.D. & ROUSE, G.H.,1988. Optimal beef cattle diets formulated by nonlinearprogramming. J. Anim. Sci. 66, 1115-1123.

HICKS, R.B., OWENS, F.N., GILL, D.R., MARTIN, J.J. &STRASIA, C.A., 1987. Effect of controlled feed intake onperformance of feedlot steers and heifers. Okla. Agric.Exp. Sta. Res. Repr. MP - 119, 320.

HICKS, R.B., OWENS, F.N., GILL, D.R., MARTIN, J.J. &STRASIA, C.A., 1988a. Effects of programmed feed intakeon performance and carcass characteristics of feedlotsteers. Okla. Agric. Exp. Sta. Res. Rep. MP - 125, 147.

HICKS, R.B., OWENS, F.N., GILL, D.R., MARTIN, J.J. &STRASIA, C.A., 1988b. Effects of weekly or bi-weeklyrotat ional feeding of lasalocid and monensin onperformance of feedlot steers. Okla. Exp. Sta. Res. Rep.MP-125, 171.

HORTON, G.M.J., 1982. Efficacy of lasalocid against coccidiain cattle and sheep. In: Roche Bovatec Symp. Proc. Eds.R.L. Stuart & C.R. Zimmerman. Scottsdale, Arizona. May4. p 44.

HUTCHESON, D.P., COLE, N.A. & McLAREN, J.B., 1984.Effects of pretransit diets and post-transit potassim levelsfor feeder calves. J. Anim. Sci. 58, 700.

HUTCHESON, D.P., 1989a. Stress Management of newlyarrived feeder cattle. SAFA Congress, March 1989,Vereniging.

HUTCHESON, D., 1989b. Nutriotional factors effect immuneresponse in cattle. Feedstuffs, April 10, p 16.

JOHNSON, B.A., 1987. Ionophore rotation research results;pooled five day trail summary. Roche Ionophore RotationProgram Symposium.

JOUBERT, D.M. & DREYER, J.H., 1965. Bull versus steer ona moderate plane of nutrition in a group-feeding trial. Proc.S. Afr. Soc. Anim. Prod. 4, 151.

KAUFFMAN, R .G. , 1978 . Bov i ne compos i t i o na linterrelationships. In: H. de Boer (Ed.) Patterns of Growthand Development in cattle. Martinus Nijhoff, The Hague.CEC. p 13.



35

KIM, Y.K. & OWENS, F.N., 1985. Starch digestion by feedlotcattle: Influence of roughage and intake level and particlesize. Oklahoma Agr. Exp. MP-117, 298.

KLINGBIEL, J.F.G., 1984. Ontwikkeling van 'n graderingstelselvir beeskarkasse. DSc (Agric) Thesis. Univ. Pretoria.

LEMIEUX, P.G., BYERS, F.M. & SCHELLING, G.T., 1988.Anabolic effects on rate, composition and energeticefficiency of growth in cattle fed forage and grain diets. J.Anim. Sci. 66, 1824.

LOFGREEN, G.P. & KIESLING, H.E., 1985. Effects of receivingand growing diets on compensatory gains of stressedcalves. J. Anim. Sci. 61, 320.

LOY, D.D., HARPSTER, H.W. & CASH, E.H., 1988. Rate,composition and efficiency of growth in feedlot steersreïmplanted with growth stimulants. J. Anim. Sci. 66, 2668.

MACGREGOR, R.C., 1988. Growth promotors and theirimportance in ruminant livestock production. In: Recentdevelopments in Ruminant Nutrition II. W. Haresign &D.J.A. Cole (Eds.), Butterworths, London. p 308.

MADER, T.L., TURGEON, O.A., KLOPFENSTEIN T.J., BRINK,D.R. & OLTJEN R.R., 1989. Effects of previous nutrition,feedlot regimen and protein level on feedlot performanceof beef cattle. J. Anim. Sci. 67, 318.

MAHMOUDZADEH, H., MUTIFERING, R.B., MITCHELL, G.E.JR. & TUCKER, R.E., 1985. Starch digestion in theprecence of lignin monomers. J. Anim. Sci. 61 (Supp. 1),483.

MARTIN, T.G., PERRY, T.W., BEESON, W.M. & MOHLER,M.T., 1978. Protein levels for bulls: Comparison of threecontinues dietary levels on growth and carcass traits. J.Anim. Sci. 47, 29.

McCARTHY, F.D., HAWKINS, D.R. & BERGEN, W.G., 1985.Dietary energy density and frame size effects oncomposition of gain in feedlot cattle. J. Anim. Sci. 60, 781.

MEAKER, H.J., 1988. Doeltreffende vleisbeesproduksie onderekstensiewe toestande. SASAP Congress. Bloemfontein.

MEAKER, H.J. & BARNARD, J.C., 1988. Beef steersimplanted with short, medium and long-acting anaboliccompounds grazing natural pastures and finished infeedlot. S. Afr. J. Anim. Sci. 18, 68.

MEAT BOARD, 1990. Expectations in the red meat industry.Agricultural Outlook Conference, February 1990, Pretoria.

MEISSNER, H.H., 1983a. Effects of energy concentration andfeeding level on growth and efficiency of beef steers. S.Afr. J. Anim. Sci. 13, 80-83.

MEISSNER, H.H., 1983b. Feeding standards for ruminants: Aprogress report of research under controlled conditions inSouth Africa. S. Afr. J. Anim. Sci. 13, 267.

MEISSNER, H.H., CAMPHER, J.P., VAN STADEN, J.H. &SHELBY, T., 1982a. Patterns of intake and digestibilty bycattle and sheep of feed mixtures with roughage source,particle size and level of inclusion as variables. S. Afr. J.Anim. Sci. 12, 319-329.

MEISSNER, H.H., VAN STADEN, J.H. & ELMA PRETORIUS,1982b. The description of growth in beef bulls andinterpretation of genotypic differences on two dietarytreatments. S. Afr. J. Anim. Sci. 12, 331.

MEISSNER, H.H. & ROUX, C.Z., 1983. Growth and feedintake patterns: 2. Application to feed efficiency. In:Herbivore Nutrition in the Sub-tropics and tropics, Eds.F.M.C. Gilchrist & R.I. Mackie. The Science Press,Johannesburg.

MERCHEN, N.R., DARDEN, D.E., BERGER, L.L., FAHEY,G.G., TITGEMEYER, E.C. & FERNANDO, R.L., 1987.Effects of dietary energy level and supplemental proteinsource on performance of growing steers and nutrientdigestibility and nitrogen balance in lambs. J. Anim. Sci.65, 658.

MOULD, F.L., 1988. Associative effects of feeds. In: WorldAnimal Science B4. Ed. E.R. Orskov. Feed Science.Elsevier Science Publishers. p 279.

NAUDÉ, R.T. , 1974. In tens iewe vle isproduks ie u i tmelkrasbeeste. DSc (Agric) Thesis. Univ. Pretoria.

NAUDÉ, R.T., 1982. Die invloed van die nuwe graderingstelselop beesvleis produksie. Simmentaler 7(1) 6, 8-10, 12-15.

NAUDÉ, R.T., HOFMEYR, J.H., DE BRUYN, J.F., ROSSOUW,E.J. & CLOETE A., 1986. The Brahman carcass andconsumer requirements. 3rd Brahman World Congress,South Africa.

NEWBOLD, J.R., 1988. Nutrient requirements of intensivelyreared beef cattle. In: Recent developments in RuminantNutrition II. Eds. W. Haresign & D.J.A. Cole), Butterworths,London. p 323.

NIXON, D.L., HATFIELD, E.E. AND LAMB, P.E., 1969.Comparison of whole shelled corn with cracked corn incattle finishing diets. J. Anim. Sci. 29, 161 (Abstract).

NRC., 1984. Nutrient Requirements of Beef Cattle. (6th Ed.)National Academy Press, Washington, DC.

NRC., 1985. Ruminant Nitrogen Usage. National AcademyPress, Washington, DC.



36

OLD, C.A. & GARRETT, W.N., 1987. Effects of energy intakeon energetic efficiency and body composition of beefsteers differing in size at maturity. J. Anim. Sci. 65, 1371.

OLTJEN, J.W. & GARRETT, W.N., 1988. Effects of bodyweight, frame size and rate of gain on the composition ofgain of beef steers. J. Anim. Sci. 66, 1732.

ORSKOV, E.R., 1986. Starch digestion in ruminants. J. Anim.Sci. 63, 1624.

OWENS, F.N., ZINN, R.A. & KIM, K.Y., 1986. Limits to starchdigestion in the ruminant small intestine. J. Anim. Sci. 63,1634.

PETERSON, E.B., STROBEHN, D.R., LADD, G.W. &WILLHAM, R.L., 1989. Effects of preconditioning onperformance of beef before and after entering the feedlot.J. Anim. Sci. 67, 1678-1686

PLEGGE, S.D., 1986. Restricting intake of feedlot cattle. FeedIntake Conference Proceedings, Okla. Agr. Exp. Sta. Misc.Publ. MP-121, 297.

POOS, M.I., HANSON, T.L. & KLOPFENSTEIN, T.J., 1979.Monensin effects on diet digestibility, ruminal proteinbypass and microbial protein synthesis. J. Anim. Sci. 48,1516.

PRIOR, R.L. & SCOTT, R.A., 1980. Effects of intravenousinfusions of glucose, lactate, propionate or acetate on theinduction of lipogenesis in bovine adipose tissue. J. Nutr.110, 2011.

REICHERT, R.D., FLEMMING, S.E. & SCHWAB, D.J., 1980.Tannin deactivation and nutritional improvement ofsorghum by anaerobic storage of H2O- HCl- or NaOH-treated grain. J. Agric. Food Chem. 28, 824.

REID, J.T., BENSADOUN, A., BULL, L.S., BURTON, J.H.,GLEESON, P.A., HAN, I.K., HOO, Y.D., JOHNSON, D.E.,McMANUS, W.R., POLADINES, O.L., STROUD, J.W.,TYRRELL, H.F., VAN NIEKERK, B.D.H. & WELLINGTON,G.W., 1968. Some peculiarities in the body composition ofanimals. In: Body composition in animals and man. Nat.Acad. Sci. 1698, 19.

ROBELIN, J. & GEAY, Y., 1983. Body composition of cattle asaffected by physiological status, breed, sex and diet. In:Herbivore Nutrition in the Subtropics and Tropics. Eds.F.M.C. Gilchrist & R.I. Mackie. The Science Press,Johannesburg.

ROBINSON, J.R., 1986. Niacin in beef cattle nutrition. Anim.Health & Nutr. April 1986, p 9.

ROMPALA, R.E., JONES, S.D.M., BUCHANAN-SMITH, J.G. &BAYLEY, H.S. , 1985. Feedlot per formance andcomposition of gain in late maturing steers exibiting normaland compensatory growth. J. Anim. Sci. 61, 637.

SCHELLING, G.T., SPIRES, H.R., MITCHELL, C.E. &TUCKER, R.E., 1977. The effect of various anti-microbialson amino acid degredation rates by rumen microbes. Fed.Proc. 36, 411.

SCHELLING, G.T., 1984. Monensin mode of action in therumen. J. Anim Sci. 58, 1518.

SIP, M., 1988. Feeding of limited high-concentrate diets mayincrease steer backgrounding profits. Feedstuffs. August22, p 16.

SHORT, D.E., BRYANT, M.P., HINDS, F.C. & FAHEY, G.C.,1978. Effect of monensin upon fermentation end productsand cell yields of anaerobic micro-organisms. J. Anim. Sci.47 (Suppl), 44.

SLABBERT, N., 1987. Graansorghum se potensiaal asvoergraan vir vleisbeeste. In: Ruminant Information Day,ADSRI, 15 September 1987, Irene.

SLABBERT, N. , LEEUW, K.J . , 1990 . Termies ge-ammoniseerde graansorghum in afrondingsdiëte vanvleisrasosse. 27-29 March 1990, SASAP Congress,Stellenbosch.

SLABBERT, N., 1990. Nutritional manipulation of growth toproduce beef carcasses of a desired composition. In,Technical communication. Dep. Agri. Development. ADSRIInformation Day, 27 September 1989, Irene. (to bepublished).

SLABBERT, N., BOLT, M.J., SHELBY, T. & CAMPHER, J.P.,1988. The utilization by beef steers of a soft high lysineand a hard normal maize cultivar in whole grain feedlotdiets. Anim. Feed Sci. and Tech. 21, 31-34.

SMITH, S.B., PRIOR, R.L., FERRELL, C.L. & MERSMAN,H.J., 1984. Inter-relationships among diet, age, fatdeposition and lipid metabolism in growing steers. J. Nutr.114, 153.

STOCK, R.A., 1988. Methods of improving feed efficiency incattle reviewed. Feedstuffs, October 10, p 18.

STOCK, R.A., BRINK, D.R., BRANDT,R.T., MERILL, J.K. &SMITH, K.K., 1987a. Feeding combinations of highmoisture corn and dry corn to finishing cattle. J. Anim Sci.65, 282.

STOCK, R.A., BRINK, D.R., BRITTON, R.A., GOEDEKEN,F.K., SINDT, M.H., KRIEKEMEIER, K.K., BAUER, M.L. &



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SMITH, K.K., 1987b. Feeding combination of high moisturecorn and dry-rolled grain sorghum to finishing cattle. J.Anim. Sci. 65, 290.

SWINGLE, R.P & MOORE, JEANNETTE A., 1987. Interactionsbetween level and tipe of roughage influence utilization ofruminant diets. In: Southwest Nutrition and ManagementConference, February 5-6, Tempe Arizona.

TOLAND, P.C., 1976. The digestibility of wheat, barley or oatgrain fed either whole or rolled at restricted levels with hayto steers. Aust. J. Exp. Agric. Anim. Husb. 16, 71-75.

TRITSCHLER, J.P., SHIRLEY, R.L. & BERTRAND, J.E., 1984.Tissue protein and energy deposition in steers feedisocaloric diets with different levels of nitrogen. J. Anim.Sci. 58, 444.

UNRUH, J.A., 1986. Effects of endogenous and exogenousgrowth promoting compounds on carcass composition,meat quality and nutritional value. J. Anim. Sci. 62, 1441.

VAN NIEKERK, A.I., 1989. Speech by the Deputy Minister ofAgriculture, at the opening of the annual SAFA Congress.Vanderbijlpark, 9 March, 1989.

VAN NIEKERK, B.D.H., 1987. Feed additives and hormone-like substances in the feeding and management of

ruminants. Refresher course 2 - 3 Feb. 1987. Univ.Pretoria.

VAN NIEKERK, B.D.H. & TARR, B., 1982. A new feedingsystem for feedlot cattle: Pram pellets fed with whole ormilled maize. S. Afr. J. Anim. Sci. 12, 306 (Abstract).

ZINN, R.A., 1986a. An evaluat ion of crude proteinrequirements of growing-finishing steers. CaliforniaFeeders Day Report, p 29.

ZINN, R.A., 1986b. Influence of type and frequency ofimplants on performance of limit-fed vs ad libitum steers.California Cattle Feeders' Day, p 47.

ZINN, R.A., 1987a. Influence of lasalocid and monensin plustylosin on comparative feeding value of steam flakedversus dry-rolled corn diets for feedlot cattle. J. Anim. Sci.65, 256.

ZINN, R.A., 1987b. Programming feed intake to improveperformance of feedlot cattle. Southwest Nutrition andManagement conference. Feb 5-6, 1987. Tempe, Arizona,p 109.

ZINN, R.A., 1989. Manger space requirements for limit-fedfeedlot steers. J. Anim. Sci. 67, 853.



38

39

N O T E S

40

N O T E S

QUANTITATIVE AND QUALITIVE ASPECTS OF

BEEF PRODUCTION BY SOME BEEF CATTLE

BREEDS IN THE RSA

J.F. DE BRUYN, R.T. NAUDÉ, J.H. HOFMEYR, W. BOK, J.A. VERMEULEN & M.C. BASSON*

Animal and Dairy Science Research Institute, Private Bag X2, Irene, 1675 Republic of South Africa*Vaalharts Research Station, Jan Kempdorp, 8550 Republic of South Africa

INTRODUCTION

Nel (1989) calculated that at the current growth rate of thepopulation in SA, the population in the RSA and TBVCcountries will be about 47,592 million by the year 2000. If thecalculated rate of the annual decline in the per capitaconsumption of beef is taken as 1,5 % (average 1955/56 to1987/88), the estimated total consumption of beef should beabout 718 600 tons by the year 2000, as compared to the 535000 ton produced in S.A. during 1989 (Abstract of AgriculturalStatistics, 1990). Pieterse (1988) projected that the figure forthe year 2000 would be about 692 000 tons (per capitaconstant) while Hofmeyr (1986) indicates that geometricgrowth tendencies and extrapolation point towards a need of810 000 tons of beef in the RSA by the turn of the century.

According to these three sources it could thus be speculatedthat the RSA would need between 700 000 and 800 000 tonsof beef by the year 2000 or 750 000 as predicted by Griessel(1979). This would mean an increase in beef production ofbetween 30,8 and 49,5 % over the next ten years, if SA wasto be self-sufficient in beef supply.

Against the background that cattle numbers in SA wouldremain fairly static at just over 8 million in the near future(Lombard, 1989), it becomes evident that the most importanttool in achieving the increased beef demand for the future isthe intensified feeding of cattle in feedlots (Griessel, 1979). Forthis purpose the maximum number of potential slaughtermaterial has to be withdrawn from natural veld as soon aspossible as to allow the utilization of natural veld in SA mainlyby increased numbers of female breeding stock (Harwin &Lombard, 1974). The feedlot industry thus has come to stayand the SA red meat industry will have to depend more andmore on the feedlot industry in the future to meet theincreased need of the consumer. Intensified research thus hasto be undertaken in the near future regarding feedlot practisesin order to ensure the optimal utilization of this industry.Extensive research overseas has shown that one of the mostimportant production aids in optimising the productionefficiency in the feedlot is the utilization of the later maturing,large framed European breeds (Robertson, 1976; Martin,Anderson & O'Mary, 1980). The importance of utilising latermaturing genotypes (sires) in beef production systems,directed at the feedlot industry, might even become of greater



41

JOHAN DE BRUYN is the group leader of the Meat Production Division at the Meat ScienceCentre at the ADSRI. He received his BSc, Bsc (Hons) and MSc (Agric) (Animal Science)degrees from the University of Stellenbosch. He is currently involved in an intensive genotypeevaluation project. Further research projects also include work on compensatory growth inbeef cattle and the relationship between degree of finishing on the live animal and the carcassin beef cattle of different maturity types.

importance in the future in view of the possibility that thebanning of anabolic growth promotants in the EEC may alsoaffect the rest of the world, including SA.

It was against this background of possible developments in SAthat it was decided in the mid 70's to initiate a genotypeevaluation programme at the Vaalharts Research Station nearJan Kempdorp, with the two main objectives being:

- the potential of a feedlot industry in SA, which has alreadyproven itself thoroughly during the last decade or two and

- the potential of especially the later maturing Europeanbreeds in such an intensive beef production system (feed-lot).

PROCEDURES

Weaner steers, of 34 different genotypes (Table 1), wereintensively fed (ME = 10,50 MJ/kg and CP = 11,86 %) inindividual feeding pens at the Vaalharts Research Station andslaughtered at the following growth stages (at the ADSRI,Irene):

- weaning (±210 days)- 340 kg- 380 kg

- 440 kg.

Growth response (average daily gain - ADG and feedconversion ratio - FCR) were monitored in each respectivegrowth stage and when a specific slaughter mass wasreached, the animals concerned were railed to the ADSRI,Irene, for slaughtering (carcasses were not electricallystimulated). Evaluations included inter alia the following:

a. Slaughter animal evaluation- Dressing percentage.

b. Carcass evaluation- Warm and cold carcass mass (chilled at 0 - 4 °C)- Carcass classification and grading- Measurements: backfat thickness, carcass and buttocklength and eye muscle width and length

- Dissection of 15 wholesale cuts in subcutaneous fat, meatand bone.

c. Meat quality evaluation- Sensory panel evaluation: Tenderness, juiciness, aromaand flavour and residual protein.

- Shear force measurement (indication of meat tenderness)



42

SIREDAM

AFRIKANER (A) BONSMARA (Bo) BRAHMAN (B) CHAROLAIS (C) HEREFORD (H) SIMMENTAL (S) TOTAL

Afrikaner (A) A (19)1 BA (15) CA (10) HA (16) SA (16) 76

Bonsmara (Bo) Bo (16) BBo (16) CBo (13) HBo(15) SBo(15) 75

Brahman(B) B (12) 12

Charolais (c) C (16) 16

Hereford (H) H (16) 16

Simmental (S) S (16) 16

BA ABA (13)2 BBA (12) CBA (14) HBA (15) SBA (13) 67

CA ACA (15) BCA (16) CCA (15) HCA (16) SCA (16) 78

HA AHA (11) BHA (13) CHA ( 9) HHA ( 7) SHA (16) 56

SA ASA (16) BSA (16) CSA (15) HSA (16) SSA (16) 79

TOTAL (74) (16) (100) (92) (101) (108) 491

1 Number of trial animals per genotype2 Sire genotype mentioned first

TABLE 1: Breeding plan and genotype numbers.

- Cooking loss (%)- Water holding capacity.

Growth and meat quality data were analysed by means ofleast-squares analysis of variance (Harvey, 1988), whilecarcass data was submitted to an analysis of co-variance(Snedecor and Cochran, 1967). The latter method of carcassanalysis has the advantage, due to the mutual comparison ofmore than one regression line within a single analysis, thatvarying numbers of genotypes can be compared against eachother, regarding the different carcass quality characteristics (y= meat %, bone %, meat in expensive cuts %, etc.), at anequal carcass fatness (x = back fat thickness, subcutaneousfat % or total fat %). For this presentation only subcutaneousfat (%) will be used as the independent variable.

For the purpose of this presentation the following comparisonswere made:

a. Six (6) purebreds (Table 1): Afrikaner (A); Bonsmara (Bo);Brahman (B); Charolais (C); Hereford (H); Simmental (S).

b. Five (5) physiological or maturity groups. The 34 differentgenotypes were classified, according to carcass mass at aspecific subcutaneous fat (%), in the following 5 physio-logical groups:

- Early- Medium-early (M-early)- Medium- Medium-late (M-late)

- Late.

Subcutaneous fat (%) was used as the criterion (independentvariable) for physiological group classification in this instanceand for carcass evaluation as to correspond with the situationin the SA classification and grading system.

RESULTS AND DISCUSSION

Growth

The analysis of variance and least-squares means of ADG andFCR for the purebreds and physiological groups are presentedrespectively in Tables 2 and 3.

Results indicate clearly the relationship between physiologicalstage of maturity (mature size) and growth rate, with the latermaturing genotypes (C and S) and groups (M-late and Late)showing the higher ADG (Tables 2 and 3). The only exceptionwas, however, the favourable growth results of the purebred H(Table 2) and the early maturing group (Table 3), whichconsisted only of H-sired genotypes. These findings are verymuch in line with those of Southgate, Cook & Kempster(1982a) regarding the positive relationship between ADG andmature size, with the H-sired genotype in their trial indeedshowing a significantly (P<0,05) lower ADG than the latermaturing crosses (C-, S- and South Devon-sired genotype).Wilson, Abdul-Jamak, LeVan, Todd, Watkins & Ziegler (1983)also recorded a significantly (P<0,05) lower ADG for the H, asopposed to the later maturing European breeds. Jones,Burgess, Wilton & Watson (1984b) confirmed these findingswith work on small and large framed animals.



43

PARAMETER CV(%) F-VALUE LEAST-SQUARES MEANSA Bo B C H S

ADG 16,30 6,660** 809a 1094b 849a 1380c 1201b 1171b

FCR 10,81 4,084** 7,87a 7,09bde 7,60abe 6,12c 6,60dc 7,27e

1 - d.f. = 33/±450; ** - P<0,01abcde Means within the same row with different superscripts differ significantly (P<0,05)

TABLE 2: Analysis of variance and least-square genotype means for ADG (g/day) and FCR (kg/kg).

PARAMETER CV (%) F-VALUE (group)1 LEAST-SQUARES MEANSEARLY M-EARLY MEDIUM M-LATE LATE

ADG 17,17 26,245** 1090ac 890b 1038a 1114c 1265d

FCR 10,95 15,509** 6,87a 7,58b 7,14c 6,82a 6,41d

1 d.f. = 33/±480; ** - P<0,01abcd Means within the same row with different superscripts differ significantly (P<0,05)

TABLE 3: Analysis of variance and least-square physiological group means for ADG (g/day) and FCR (kg/kg).

FCR results (Tables 2 and 3), as evaluated on a constantmass basis, showed the usual direct relationship with ADG.The later maturing genotypes and groups and the earlymaturing H and group consequently showed the mostfavourable FCR results. A small deviation from the expectedwas the relatively poorer FCR of the S, as compared to thisgenotype's ADG-position (Table 2). Mentz, Els & Coetzer(1979) found almost similar results in a study, that precededthis study at Vaalhartz, viz. the C-, H- and S-sired genotypeshad significantly (P<0,05) more efficient FCR results than theBos indicus-sired genotypes (A- & B-sire), with the S-siredgenotypes having the least efficient FCR regarding the formerthree sires. If growth test results (1980 - 1985) of Phase C ofthe National Beef Cattle Performance and Progeny TestingScheme are, however, considered the H and S showed almostsimilar FCR results (6,86 vs 6,96). Smith, Laster, Cundiff &Gregory (1976) and Cundiff, Koch, Gregory & Smith (1981)found in both their studies that at a constant mass basis thelater maturing genotypes had significantly (P<0,05) moreefficient FCR results than their earlier maturing counterparts. Inthe first study C- and S-sired genotypes were significantly(P<0,05) more efficient than the H-, Angus- and Jersey-siredgenotypes, while the later maturing Brown Swiss-, Gelbvieh-and Main Anjou-sired genotypes were again more efficient inconverting feed to live mass than the early-maturing Red Poll-,H- and Angus-sired genotypes in the latter study.

The well documented leaner carcass of the later maturinggenotypes at a constant mass basis (Norman & de Felicio,1982; Swortzel, Marlowe, Notter, Kelly & Tolley, 1984) hasbeen shown to be directly responsible for their morefavourable FCR results. The ideal should thus be to compareanimals of different maturity types at a constant carcassfatness, which would also correspond with the situation inindustry where most of the animals are slaughtered withincertain target grades of specific fatnesses. For this specificpurpose the FCR was predicted, by means of regressionsubstitution, for each genotype and physiological group at aspecific subcutaneous fat (%) in the carcass. Thesubcutaneous fat (%) chosen, viz. 6,8 %, is only an arbitraryvalue to highlight genotype and group differences and due tothe parallelism of the respective regression lines, genotypes orgroups will show exactly the same FCR differences at anysubcutaneous fat (%). The predicted FCR values at a specificsubcutaneous fat (%) are presented in Table 4.

In contrast to FCR results on a constant mass basis (Tables 2and 3), the later maturing C and S and especially the M-lateand Late groups on a subcutaneous fat constant basis, hadhigher FCR values (less efficient) than the earlier maturinggenotypes (A, Bo, B and H) and groups Early and M-early(Table 4). These differences seem to correlate closely withgenotype and group differences in carcass mass, and couldthus most probably be attributed or partially attributed to

differences in maintenance requirements. Southgate et al.(1982a) and Southgate, Cook & Kempster (1982b) alsocompared different genotypes at a constant subcutaneous fatbasis in the carcass (g/kg) and findings regarding FCR weresimilar to those in this study. Their studies also involved awide range of different maturity types and almost consistentlythe H-sired genotypes had the most favourable FCR on thisbasis of evaluation (constant subcutaneous fat). Southgate etal. (1982b) gave the following factors as possible explanationsfor the apparent superiority of H-crosses in FCR, viz.

i. Higher intrinsic efficiency (digestive and metabolic effi-ciency) leading to a lower heat production.

ii. Differences in overall maintenance requirements betweenearlier- and later-maturing genotypes because of:

- differences in number of days to slaughter and- differences in slaughter mass.

iii. Differences in body composition at the beginning of thetrial, such that earlier-maturing genotypes would need todeposit proportionally less fat than would late-maturinggenotypes to a constant fatness endpoint.

iv. Differences in body composition and hence energy depo-sition at equal subcutaneous fat (%) due either to differ-ences in fat partitioning or to inaccuracies in the predictionof the actual carcass subcutaneous fat (%).



44

FCR (MJDE/KG) COLD CARCASSMASS(KG)

PUREBREDS:A 72,88 174,65Bo 72,85 205,69B 68,44 177,75C 78,60 260,17H 63,12 150,20S 80,14 230,41

PHYSIOLOGICALGROUPS:

EARLY 64,60 159,52M-EARLY 70,64 180,10MEDIUM 74,65 205,48M-LATE 77,84 229,71LATE 78,83 258,89

TABLE 4: Predicted FCR's of the different purebredsand physiological groups at a specificsubcutaneous fat (%).

Genotype differences in fat partitioning might also have beenof importance in this study if results in Table 6 are taken intoaccount. At a specific subcutaneous fat (%) the later maturinggenotypes and groups tended to deposit a higher proportion ofintermuscular fat in their carcasses, when compared to earlymaturing types. Cundiff et al. (1981) and Cundiff, Koch &Gregory (1984) evaluated their respective genotypes at a fattrim constant endpoint of 18,9 % and found the similar trendsas above. In the first study the early maturing H- and Angus-crosses were the most efficient while the latest maturinggenotypes (Chianina-crosses) were significantly (P<0,05) lessefficient than all the other genotypes, evaluated. In the secondstudy (Cundiff et al., 1984) the H- and Angus-crosses werealso the most efficient. In these two studies a strongrelationship was found between efficiency and number of daysor NEM (net energy maintenance) required to reach theendpoint.

An additional aspect that is also of importance in determiningthe eventual efficiency of beef production (herd efficiency:kgoffspring sold/total feed ingested by the whole herd) is theconcept of feeder/breeder dimorphism or slaughter animal:dammass ratio (Roux & Scholtz, 1987; Roux, 1988). The degree offeeder/breeder dimorphism utilization in any meat productionsystem would thus depend on the extent to which the mass ofthe slaughter animal (offspring) could be increased relative tothat of the dam. A system in which large offspring for slaughtercould be produced from small dams with low maintenancerequirements, rather than the normal large dam, would thus bemore efficient. One way to increase feeder:breeder mass ratiois by means of terminal cross-breeding, e.g. the combination ofspecific dam- and sire-lines which are favourable regarding thefollowing characteristics (Roux, 1988):

Dam-line

- Fertility- Viability- Longevity- Small cow with low maintenance- Pre-weaning growth of offspring (milk production)- Adaptability.

Sire-line

- Large size (late maturing)- Post-weaning growth rate and efficiency- Calving ease of cross-bred offspring- Carcass and meat quality characteristics.

The highest slaughter animal mass (subcutaneous fat =6,8 %): dam mass ratio in the present study was observed inthe CA two-way cross, viz 0,854. The potential of the latermaturing sire-genotypes (C & S) in being responsible for themore favourable feeder/breeder dimorphism is thus very mucha certainty, if the following feeder/breeder dimorphismaverages of the five major sire-genotypes, used in combinationwith dams of the same genetic background and average mass,are considered:

The advantage of especially the later maturing C-sire canfurther be highlighted in the A two-way crosses, where the A-dam was combined in a crossbreeding system with sires, otherthan the A itself. The feeder/breeder dimorphism of the A two-way crosses are as follows:

Carcass quality characteristics

The analysis of co-variance and common correlationcoefficients (r) and residual standard deviations (R.S.D.) of the



45

SIRE FEEDER*/BREEDER DIMORPHISM

A 0,643

B 0,656

C 0,787

H 0,604

S 0,736(* - slaughtered at subcutaneous fat = 6,8 %)

A TWO-WAY CROSSES FEEDER/BREEDERDIMORPHISM

A 0,672BA 0,731 (+8,8%*)CA 0,854 (+27,1%)HA 0,627 (-6,7%)SA 0,772 (+14,9%)

(* - percentage improvement in feeder/breeder dimor-phism relative to the purebred A)

relationship x = subcutaneous fat (%) and y = respectivecarcass quality characteristic are presented in Table 5.

Results in Table 5 demonstrate a distinct genotype/maturityeffect which was not taken into account when developing theS.A. beef carcass classification and grading system. The aimwas to classify car-significant genotype/group effect, with allthe other carcass characteristics showing highly significant(P<0,01) genotype/group effects (Table 5). The non-significantgenotype/group effect on for instance muscle (%) in thecarcass would mean that irrespective of genetic background orphysiological status of the animal, muscle (%) in the carcasswould remain constant and a common regression line could befitted for all genotypes or physiological groups. It is thusevident that the SA beef carcass classification and gradingsystem does group carcasses correctly in terms of muscle (%)but significant variations are very much thee order of the dayas far as bone and fat (%) are concerned. The respectivecommon lines for x = subcutaneous fat (%) and y = muscle(%) in the carcass in this study are as follows:

Genotypes: y = 77,86 - 1,7423 x

Physiological groups: y = 77,64 - 1,6993 x

All the carcass quality characteristics that showed a significant(P<0,01) genotype/group effect expressed the specific effect insignificant (P<0,01) elevation (intercept)-differences (Table 5).The rate (slope) at which these different carcass componentschanged with an increase in subcutaneous fat (%) were thussimilar for all genotypes or physiological groups and commonslopes could thus be used in each respective relationship.Elevation or adjusted mean differences for the respectivecharacteristics thus indicate that genotype/group differenceswere already established at the commencement of this trialand that these differences were maintained throughout thewhole period. The elevations of the different dependentvariables (y) for the 6 purebreds and 5 physiological groupsare presented in Table 6.

Dressing percentage results showed a strong positiverelationship with the stage of maturity. The latest maturingpurebred (C) had a significantly (P<0,05) higher elevation forthis characteristic than all the other purebreds while asignificant (P<0,05) increase in dressing percentage wasevident for each increase in the stage of maturity (Table 6).Kempster, Cook & Southgate (1982a) also found a closeassociation between the stage of maturity, hence carcass



46

CHARACTERESTIC (Y) ANALYSIS OF COVARIANCE r R.S.D.F-SLOPE F-ELEVATIONS

GENOTYPES1

1) DRESSING PERCENTAGE (%) 1,61 5,20** 0,60 2,02802) MUSSLE IN CARCASS (%) 1,28 1,27 -0,81 3,34303) BONE IN CARCASS (%) 1,46 5,20** -0,83 0,98984) TOTAL FAT IN CARCASS (%) 1,45 52,08** 0,87 3,60375) MUSCLE FAT IN CARCASS (%) 1,46 1,94** 0,70 3,70696) MEAT IN CARCASS (%) 1,44 5,28** -0,75 0,99577) MUSCLE : BONE RATIO 0,94 2,95** 0,37 0,66098) MEAT IN MORE EXPENSIVE CUTS (%) 1,39 1,83** -0,77 0,9942PHYSIOLOGICAL GROUPS2

1) DRESSING PERCENTAGE (%) 0,95 26,03** 0,60 2,15972) MUSCLE IN CARCASS (%) 1,56 1,62 -0,78 3,70193) BONE IN CARCASS (%) 1,82 27,62** -0,81 1,06184) TOTAL FAT IN CARCASS (%) 1,57 6,60** 0,84 3,99785) MUSCLE FAT IN CARCASS (%) 1,33 6,35** 0,66 4,03186) MEAT IN CARCASS (%) 1,58 26,97** -0,75 1,04977) MUSCLE : BONE RATIOc �- �- 0,268) MEAT IN MORE EXPENSIVE CUTS (%) 2,31 1,32 -0,75 1,06551 - d.f. (F-values) = 33/±450; ** = P<0,012 - d.f. (F-values) = 4/±480; ** = P<0,01c - Analysis of variance (r<0,30): F (genotype) = 2,39 NS.

TABLE 5: Analysis of covariance and common correlation coefficients (r) and R.S.D.'s

mass at a constant subcutaneous fat content (67 g per kgcarcass: 6,7 %) and dressing percentage. In their study the C-sired genotypes also had the most favourable dressingpercentage, which was confirmed in a further study by theseresearchers (Kempster, Cook & Southgate, 1982b). Jones,Rompala, Wilton & Watson (1984a) also found that largeframed animals, which were slaughtered 38,7 % heavier thansmall framed animals at a constant back fat thickness, weresuperior in dressing percentage. They ascribed thesedifferences to the small framed animal having a proportionalhigher body yield of head, hide, liver, omasum and smallintestines. Of the early maturing purebreds, however, afavourable dressing percentage was especially noticeable inthe B (Table 6). The B had an elevation significantly (P<0,05)larger than both the H and A and non-significantly differentthan the late maturing S and medium maturing Bo (Table 6).Solomon, West & Hentges (1982) reported similar findings inBrahman bulls, when compared with Angus bulls at the samepercentage of the average mature cow mass.

Due to the uniformity in the fat free edible portion of thecarcass (muscle %) between different genotypes andphysiological groups (Table 5), significant (P<0,01) differencesin carcass composition had been expressed in bone (%) andtotal fat (%), hence intermuscular or muscle fat (%)

(subcutaneous fat % constant), in the carcass. Bone (%)showed, similar to dressing percentage, a direct relationshipwith the stage of maturity of the animal (Table 6). The latermaturing C and S had significantly (P<0,05) smaller elevationsfor bone (%) than all the other purebreds with H showing theleast favourable relative bone yield in the carcass. Elevationsfor bone (%) also decreased significantly (P<0,05) with eachincrease in physiological stage (Table 6). Bone (%) thus alsoseemed to be influenced rather by the slaughter mass of therespective purebreds and physiological groups than by carcassfatness. Jones et al (1984a) reported similar findings in smalland large framed animals, evaluated at 18,7 % total fat in thecarcass. The large framed animals with carcass masses 41,9% (96,7 kg) heavier than those of the small framed animals,had significantly (P<0,05) smaller bone percentages (16,5 vs.18,3 %) in the carcass. Koch, Dikeman, Allen, May, Crouse &Campion (1976) and Koch, Dikeman, Lipsey, Allen & Crouse(1979), however, found no significant differences in bone (%)in the carcasses of animals, varying widely in maturity, whenevaluated on a constant total fat trim (%). These researchersevaluated the animals in their studies respectively at aconstant age, carcass mass, fat thickness, fat trim andmarbling basis and found that the smallest between-genotypedifferences in bone (%) existed when fat trim or fat thicknesshad been used as the basis of comparison.



47

DRESSING (%) BONE (%) TOTAL FAT (% MUSCLE FAT (%) MEAT (%) MUSCLE:BONE EXPENSIVEMEAT (%)

PUREBREDS:COMMON SLOPE 0,5778 -0,5615 2,3912 1,3822 -0,4343 0,0632 -0,4570A 52,721a 18,565ac 3,347 3,412 81,406ac 4,083ac 46,877ac

Bo 54,866b 18,067a 3,495 3,557 81,905a 4,251ad 46,417ac

B 55,561b 18,653ac 3,041 3,115 81,313ac 4,082ac 47,105a

C 57,647c 16,416b 5,401 5,428 83,574b 4,748b 46,646ac

H 51,710a 18,911c 2,839 2,925 81,049c 3,932c 45,652b

S 54,702b 17,133b 5,313 5,353 82,848b 4,420d 46,308cb

PHYSIOLOGICAL GROUPS:COMMON SLOPE 0,5961 -0,5507 2,3189 1,3262 -0,4453 - -EARLY 52,663a 18,635a 2,598a 2,528a 81,328a 4,645* -M-EARLY 54,008b 18,290b 2,952a 3,023a 81,693b 4,692 -MEDIUM 55,051c 17,768c 3,691a 3,643a 82,215c 4,753 -M-LATE 55,658d 17,200d 5,351b 5,338b 82,780d 4,771 -LATE 57,366e 16,467e 5,804b 5,780b 83,425e 4,889 -

* Least-square meansabcde Elevations within columns of the purebreds and physiological groups with different superscripts differ significantly (P<0,05)Muscle fat (%) = total fat (%) - subcutaneous fat (%) = intermuscular fat (%)

TABLE 6: Elevations of the relationship x = subcutaneous fat (%) and y = carcass quality characteristics for the purebredsand physisological groups

The specific purebred and physiological group differences inbone (%), were directly responsible for almost similar purebredand group differences in meat (%) and muscle:bone ratio(Table 6). Since muscle (%) was very uniform, muscle:bonedifferences would follow almost a similar pattern as bone (%),while a similar tendency would be evident for meat (%) (meat% = carcass less bone % + subcutaneous fat % - constant).Bone and meat (%) as a result showed the exact between-purebred and physiological group differences (Table 6). Thelater maturing purebreds (C & S) and physiological groups withthe smallest proportional bone yield showed the highestelevations for meat (%). Similar findings were also noticeablefor muscle:bone ratio in the purebreds. Although a tendencydid exist for the later maturing groups to show a highermuscle:bone ratio, these differences were not significant.Kempster et al. (1982a) also showed a higher saleable meatyield in the carcass (g/kg) of the later maturing C-sired animalsas opposed to the early maturing H-sired animals in their 16-month production system. In this system, however, the earlymaturing Angus- and Sussex-sired genotypes were similar tothe C-sired genotypes in saleable meat yield (%). Results fromthe 24-months production system (Kempster et al., 1982a) anda further study by these researchers (Kempster et al., 1982b)also were very much variable regarding saleable meat (%),and hence meat:bone ratio. Sires such as the later maturing Cand Limousin and the early maturing Angus and Sussex wereespecially responsible for favourable meat yields (%) in thecarcasses of their offspring, while animals, sired by inter aliathe Hereford, Friesian and Lincoln Red, produced carcasseswith less favourable meat yields (%) (Kempster et al., 1982a,1982b). In contrast to the strong physiological stage effect onmeat (%) and muscle:bone ratio in the present study (Table 6),Kempster et al. (1982a, 1982b) indicated a tendency rathertowards a specific genotype effect. Carcasses in the studies ofKempster et al. (1982a, 1982b) were also evaluated on aconstant subcutaneous fat (%) basis.

Besides the major effect of bone (%) on carcass compositionthe other aspect of importance seemed to be related to agenotype and physiological group effect on the partitioning offat between the major fat depots. By keeping subcutaneous fat(%) constant a tendency towards a higher carcass yield of totalfat (%) in the later maturing animals pointed towards aproportional higher depositioning of fat in the intermuscular fatdepot of these animals. Although not significantly so, the latermaturing C and S had higher elevations for muscle fat (%),hence total fat (%), as compared to the early maturingpurebreds (Table 6). The significantly (P<0,05) higherelevations for the M-late and Late group for thesecharacteristics, especially highlighted this phenomenon (Table6). Charles & Johnson (1976) largely confirmed thisphenomenon also by using the analysis of co-variance as theirbasis of statistical analysis. These reseachers for instancefound that if total fat (%) in the carcass were to be kept

constant (x = total fat %), the C would have had 6,6 % moreintermuscular fat and consequently 6,6 % less subcutaneousfat than the H in the carcass. Kempster, Cuthbertson &Harrington (1976) also concluded that if subcutaneous fat wereto be used to predict total fat in the carcass, biased resultswould be obtained between genotypes, due to significantgenotype differences in the distribution of fat in theintermuscular fat depot. They found a close relationshipbetween kidney and channel fat and intermuscular fat andassumed that the combination of subcutaneous and kidneyand channel fat would improve the accuracy of predicting totalfat more uniformly between genotypes.

Significant (P<0,05) purebred differences in the distribution ofmeat in the more expensive cuts (%) were primarily broughtabout by the unfavourable elevation of the H, as comparedespecially to that of the B (Table 6). The H had a significantly(P<0,05) smaller elevation than the A, Bo, B and C, while theB was also significantly (P<0,05) more favourable for thischaracteristic than the later maturing S. Genotype-differencesin the distribution of meat in the more expensive cuts (%) thusseemed to be related to a specific genotype effect rather thanthe physiological status of the animal. Kempster et al. (1982b)did, however, find a tendency for the later maturing genotypes(C-, S- and Limousin-sired) to show a significantly (P<0,05)higher carcass yield of more expensive meat (%) than theirearlier maturing counterparts. Although Koch, Dikeman &Cundiff (1982) also found significant genotype differences inthe distribution of meat in the higher priced cuts (evaluatedconstant fat trim = 19,8 %), they concluded, similar toKempster et al. (1982b), that these differences were small andof little economical advantage.

Meat quality characteristics

The analysis of variance and least-squares means for thepurebreds and physiological groups of a few meat qualitycharacteristics are presented respectively in Tables 7 and 8.

In both Tables 7 and 8 the only characteristics that showed asignificant genotype or physiological group effect were thoserelated to meat tenderness, viz. tenderness (P<0,01; Table 7)and residual protein and shear force (P<0,01; Table 7 andP<0,05; Table 8). Neither genotype nor the physiologicalstatus of the animal had a significant effect on juiciness andaroma and flavour while tenderness was also not influencedsignificantly by physiological group. The taste panel identifiedthe two later maturing purebreds (C and S) and the earlymaturing B to be characterised by significantly (P<0,05) lesstender meat, as compared to the A, Bo and H (Table 7). Shearforce results especially confirmed the tendency in the S and Bto produce less tender meat. The S had a significantly(P<0,05) higher shear force value than all the other purebreds,except the B, while the latter genotype was also significantly



48

(P<0,05) less tender (higher shear force) than the H (Table 7).S- and B-associated genotypes were also found in the othergenotype comparisons in this study (two-way crosses andthree-way crosses) to have less tender meat. The significantlyless tender meat (higher shear force) of physiological groupsMedium and M-late, as compared especially to Early (Table 8),is directly due to a higher concentration of B- and S-associated genotypes in these two groups. The less tendermeat of the B or B-crosses has already been shown by anumber of researchers (Koch, Dikeman & Crouse, 1982; Koch,Crouse & Seideman, 1987) while the work of McAllister,Wilson, Ziegler & Sink (1976), Wilson et al. (1983) and Cross,Crouse & MacNeil (1984) failed to indicate significantly lesstender meat for the S, as compared inter alia to the C, H andAngus. Koch et al. (1976) did, however, find significantly lesstender meat in S-sired genotypes, as compared to H-, Angus-,Jersey-, South Devon- and C-sired genotypes. In their study

Jersey- and South Devon-sired genotypes had the most tendermeat while genotypes, sired by the Limousin, fell into the samecategory of less tender meat of the S. In the latter study andalso in this study it should, however, be borne in mind that therespective genotype evaluations were carried out on aconstant mass basis, with the later maturing genotypes (C &S) significantly leaner than the earlier maturing genotypes. Thelater maturing genotypes were thus most probably submitted toa higher degree of cold shortening and hence less tendermeat as observed as such in the S. However, comparing thetenderness results of the late maturing S and C, the morefavourable results of the C indicate that irrespective of apossible higher degree of cold-shortening in these animals, theS might still possess an inherent tendency towards less tendermeat.



49

CHARACTERISTIC CV (%) F VALUE(genotype)

LEAST-SQUARES MEANA Bo B C H S

TASTE PANEL1:TENDERNESS 29,36 2,233** 3,09a 2,93a 2,02b 2,30b 3,17a 2,19b

JUICINESS 11,64 0,985 3,46 3,45 3,40 3,32 3,41 3,36AROMA & FLAVOUR 10,16 1,441 3,57 3,54 3,21 3,34 3,56 3,24

RESIDUAL PROTEIN 16,69 2,139** 4,22a 4,18a 3,35b 3,45b 4,32a 3,60b

SHEAR FORCE(N/2,5 mm dia)

31,02 2,385** 139,50ab 146,9ab 166,1bc 158,1ab 130,8a 190,1c

F (genotype) = 1,49 (P<0,05) & 1,74 (P<0,01)1 = Point scale out of 5: 5 = most favourable and 1 = least favourableabc Means within the same row with different superscripts differ significantly (P<0,05)

TABLE 7: Analysis of variance and least-square genotype means for certain meat quality characteristics of the purebreds.

CHARACTERISTIC CV (%) F-VALUE (group)1 LEAST-SQUARES MEANEarly Medium-early Medium Medium-late Late

TASTE PANEL:TENDERNESS 30,21 1,888 2,95 2,73 2,79 2,71 2,49JUICINESS 11,62 1,364 3,43 3,48 3,39 3,48 3,37AROMA & FLAVOUR 10,30 1,335 3,50 3,45 3,42 3,39 3,38RESIDUAL PROTEIN 17,13 2,410* 4,12a 3,93ab 3,94ab 3,88b 3,71b

SHEAR FORCE (N/2,5cm dia.) 32,02 3,035* 132,50a 143,4ab 150,1bc 156,2c 147,4abc1F (Group) = 2,39 (P<0,05) & 3,36 (P<0,01)abc Means within the same row with different superscripts differ significantly (P<0,05)

TABLE 8: Analysis of variance and least-square group means for certain meat quality characteristics of the physiologicalgroups.

CONCLUSIONS

Production and quality characteristics in this study emphasizethe enormous potential being locked up in the utilization oflater maturing genotypes, especially those sired by the C, inan intensive beef production system. Favourableconsiderations regarding these animals, or more specificallythe C, include the following:

i. High ADG

ii. Very favourable feeder/breeder dimorphism, especiallywhen combined with relatively small dams. Under S.A. ex-tensive production system consider inter alia the followingdams: Afrikaner, Nguni, Brahman, Bonsmara, BelmontRed and Tuli with selection goals been spelled out on pg45.

iii. High dressing percentage, which has the significant eco-nomic benefit in being responsible, together with the finalgrade, for the final income per animal.

iv. Favourable muscle:bone and meat:bone ratios especiallydue to a smaller bone (%) yield in the carcass. Highermeat (%) yield, however, partially due to a larger deposi-tioning of intermuscular fat.

v. Meat quality of C-sired genotypes, especially regardingmeat tenderness, compared favourably with those geno-types identified to produce the most tender meat, viz. Hand A.

It is thus evident that if SA wants to meet the ever increasingbeef demand for the future, both quantitatively andqualitatively, and also be economically competitive with otherprotein sources, later maturing sires such as the C have to beincluded to a greater extent in terminal cross-breedingprogrammes in combination with specialized dam-lines. Ahigher incidence of dystocia in especially C - sired calves (Els,1988), however, would necessitate the following adjustmentsto such terminal cross-breeding programmes:

i. Identification of certain late maturing sire-lines with a verylow incidence of dystocia by means of progeny-testing.

ii. Utilization of late maturing sires primarily on mature cows(not heifers).

REFERENCES

CHARLES, D.D. & JOHNSON, F.R., 1976. Breed differencesin amount and distribution of bovine carcass dissectablefat. J. Anim. Sci. 42, 332.

CROSS, H.R., CROUSE, J.D. & MacNEIL, M.D., 1984.Influence of breed, sex, age and electrical stimulation oncarcass and palatability traits of three bovine muscles. J.Anim. Sci 58, 1358.

CUNDIFF, L.V., KOCH, R.M., GREGORY, K.E. & SMITH, G.M.,1981. Characterization of biological types of cattle (CycleII). IV. Post weaning growth and feed efficiency of steers.J. Anim. Sci. 53;332.

CUNDIFF, L.V., KOCH, R.M. & GREGORY, K.E., 1984.Characterization of biological types of cattle (Cycle III). IV.Postweaning growth and feed efficiency. J. Anim. Sci. 58,312.

ELS, D. L., 1988. Kruisteling vir vleisproduksie. PhD Thesis,Univ. Orange Free State.

GRIESSEL, M., 1979. A protein utilization strategy for SouthAfrica. S. Afr. J. Anim. Sci. 9, 119.

HARVEY, W.R., 1988. User's guide for LSMLMW. PC-1version. January, 1988.

HARWIN, G.O. & LOMBARD, J.H., 1974. Intensification of thebeef-cow herd. S. Afr. J. Anim. Sci. 4, 247.

JONES, S.D.M., ROMPALA, R.E., WILTON, J.W. & WATSON,C.H., 1984a. Empty body weights, carcass weights andoffal proportions in bulls and steers of different maturesize. Can. J. Anim. Sci. 64, 53.

JONES, S.D.M., BURGESS, T.D., WILTON, J.W. & WATSON,C.H., 1984b. Feedlot performance, carcass compositionand efficiency of muscle gain in bulls and steers ofdifferent mature size slaughtered at similar levels offatness. Can. J. Anim. Sci. 64, 621.

KEMPSTER, A.J., CUTHBERTSON, A. & HARRINGTON, G.,1976. Fat distribution in steer carcasses of different breedsand crosses. 1. Distribution between depots. Anim. Prod.23;25.

KEMPSTER, A.J., COOK, G.L. & SOUTHGATE, J.R., 1982a. Acomparison of the progency of British Friesian dams anddifferent sire breeds in 16- an 24-month beef productiosystems. Anim. Prod. 34, 16.

KEMPSTER, A.J., COOK, G.L. & SOUTHGATE, J.R., 1982b. Acomparison of different breeds and crosses from thesuckler herd. 2. Carcass characteristics. Anim. Prod. 35,99

KOCH, R.M., DIKEMAN, M.E., ALLEN, D.M., MAY, M.,CROUSE, J.D. & CAMPION, D.R., 1976. Characterizationof biological types of cattle. III. Carcass composition,quality and palatability. J. Anim. Sci. 43, 48.



50

KOCH, R.M., DIKEMAN, M.E., LIPSEY, R.J., ALLEN, D.M. &CROUSE, J.D, 1979. Characterization of biological typesof cattle (Cycle II). III. Carcass composition, quality andpalatability. J. Anim. Sci. 49, 448.

KOCH, R.M., DIKEMAN, M.E. & CROUSE, J.D., 1982.Characterization of biological types of cattle (Cycle III). III.Carcass composition, quality and palatability. J. Anim. Sci.54, 35.

KOCH, R.M., DIKEMAN, M.E. & CUNDIFF, L.V., 1982.Characterization of biological types of cattle (Cycle III). I.Carcass wholesale cut composition. J. Anim. Sci. 54, 1160.

KOCH, R.M., CROUSE, J.D. & SEIDEMAN, S.C., 1987. Bison,Brahman and Hereford carcass characteristics,. J. Anim.Sci. 65 (Supl. 1), 124.

LOMBARD, J., 1989. Neiging in die beesvleisbedryf inoënskou. Bylae in Landbouweekblad 10 Februarie 1989.

MARTIN, E.L., ANDERSON, D.C. & O'MARY, C.C., 1980.Carcass traits of and preweaning creep feeding effects onsteers sired by Angus, Holstein, Simmental and Chianinabulls. J. Anim. Sci. 50, 62.

McALLISTER, T.J., WILSON, L.L., ZIEGLER, J.H. & SINK,J.D., 1976. Growth rate, carcass quality and fat, lean andbone distribution of British- and Continental-siredcrossbred steers. J. Anim. Sci. 42, 324.

MENTZ, A.H., ELS, D.L. & COETZER, W.A., 1979.Crossbreeding with Afrikaner dam as basis. 3. Post-weaning growth performance of progeny of various sirebreeds. S. Afr. J. Anim. Sci, 9, 209.

NEL, P., 1989. The medium and long-term prospects for thered meat industry. RPO Conference, Royal Hotel, Durban,1989-06-14.

NORMAN, G.A. & DE FELICIO, P.E., 1982. Effect of breed andnutrition on the productive traits of Zebu, Charolais andcrossbreed beef cattle in South-East: Brazil, Part 2 -Tissue distribution and carcase composition. Meat Sci. 6,1.

PIETERSE, F.P., 1988. Openingsrede, Afrikanerbeesdag, 21September 1988.

ROBERTSON, A., 1976, Why do we crossbred? Commissionof the European Communities. Crossbreeding experimentsand strategy of beef utilization to increase beef production.Eds. I.L. Mason & W. Pabst. p. 4.

ROUX, C.Z. & SCHOLTZ, M.M., 1987. Teeltdoelwitte viroptimale vleisproduksie. SASAP Congress, 1987.

ROUX, C.Z., 1988. Formulating breeding strategies for totalherd efficiency. ADSRI, Irene.

SMITH, G.M., LASTER, D.B., CUNDIFF, L.V. & GREGORY,K.E., 1976. Characterization of biological types of cattle. II.Postweaning growth and feed efficiency of steers. J. Anim.Sci. 43, 37.

SNEDECOR, G.W. & COCHRAN, W.G., 1967. Statisticalmethods. 6th Ed. Chapter 14. The Iowa State UniversityPress, Ames, Iowa, USA.

SOLOMON, M.B., WEST, T.L. & HENTGES, J.F., 1982. Effectof breed, slaughter weight and electrical stimulation oncarcass and meat characteristics of young bulls. J. Anim.Sci. 55, 13.

SOUTHGATE, J.R., COOK, G.L. & KEMPSTER, A.J., 1982a. Acomparison of the progeny of British Friesian dams anddifferent sire breeds in 16- and 24-month beef productionsytems. 1. Live-weight gain and efficiency of foodutilization. Anim. Prod. 34, 155.

SOUTHGATE, J.R., COOK, G.L. & KEMPSTER, A.J., 1982b. Acomparison of different breeds and crosses from thesuckler herd. I. Live-weight growth and efficiency of foodutilization. Anim Prod. 35, 87.

SWORTZEL, M.A., MARLOWE, T.J., NOTTER, D.R., KELLY,R.F. & TOLLEY, E.A., 1984. Sire breed effects in matingwith Angus cows. II. Carcass characteristics of steerprogeny. J. Anim. Sci, 59, 23.

WILSON, L.L., ABDUL-JAMAK, E., LEVAN, P.J., TODD, R.F.,WATKINS, J.L. & ZIEGLER, J.H., 1983. Effect of season ofbirth, breed of sire and sex of calf in a single-suckledAberdeen Angus Holstein beef herd. Anim. Prod. 37, 365.



51



52

N O T E S

BEEF, LAMB AND MUTTON CARCASS

CLASSIFICATION AND GRADING IN SOUTH

AFRICA

R.T. NAUDÉ, J.F.G. KLINGBIEL* & G.G. BRUWER*

Meat Science Centre, Animal and Dairy Science Research Institute, Private Bag X2, Irene, 1675Republic of South Africa

*Present address: Meat Board, P.O. Box 40051, Arcadia, 0007 Republic of South Africa

INTRODUCTION

Grading and classification of carcasses and meat is beingpracticed in many countries of the world in one form oranother. The object of using a specific system varies fromcountry to country, due to differences in prevailing productionand marketing conditions. A common goal which is usuallyfound, is that carcasses with similar characteristics aregrouped together in definable homogeneous categories. Theseare then applied through descriptive classification systems orin groups in order of excellence in grading systems. Gradingsystems are often rather complicated. This is due mainly to theprinciple of complementarity being employed, in which a rangeof carcass and meat characteristics contribute to thecomposition of a specific quality grade. The nature of thiscombination of traits should then determine the level ofexcellence of the carcasses and meat of a particular grade.Conformation, fat cover, size and internal fat of a carcass aswell as age or maturity of animal, marbling, colour and textureof the muscle and colour and firmness of the fat are some ofthe carcass and meat traits taken into consideration whendetermining the grade of a carcass. Classification systems, in

which similar parameters are used to those in gradingsystems, are however, in contrast to grading systems,relatively simple. In these systems, carcass and meatcharacteristics are merely described and listed in an increasingor decreasing quantitative order, which are not necessarily inorder of excellence.

In certain countries of the world grading and/or classificationsystems exist in order to facilitate a marketing practice inwhich a certain price is linked to a specific grade or class ofcarcass. This may be a fixed or a minimum guarantee price.The object of such a procedure would be to create anincentive for producing a particular type of carcass, in order todirect production and marketing trends to the benefit of allparticipating factors in the meat industry i.e. producers, middlemen and consumers alike. Such a system of classification andgrading of carcasses exists in South Africa in terms of theMarketing Act, 1968 (Act 59 of 1968), and is applied on amandatory basis in the �controlled� urban areas of the country,where more than 65 % of the red meat (61 % cattle, 74 %



61

RAYMUND NAUDÉ is Deputy Director at the ADSRI, Irene and is responsible for the sub-directorate of Animal Physiology and Meat Science. He attained the degree DSc (Agric) at theUniversity of Pretoria in 1974 with a thesis entitled �Intensive meat production with DairyCattle�. Under his guidance the Meat Science Centre, financed by the Meat Board, wasestablished at Irene, where meat research from �conception to consumption� is undertaken bya team of scientists. He has travelled widely internationally, presenting research papers andinvited lectures and visiting many of the leading meat research papers and invited lecturesand visiting many of the leading meat research laboratories of the world. He was awarded theSilver medal for high standing research by the S.A. Society for Animal Production (1977), theGold medal for agricultural leadership of the Witwatersrand Agricultural Society (1982) as wellas being named the �Agricultural Scientist of the Year� (1986) by the Agricultural WritersAssociation of South Africa.

sheep and 50 % pigs) is being marketed in carcass formthrough an auction-on-the-hook system. The system is alsoapplied on a voluntary basis in the �uncontrolled� rural areas ofSouth Africa. For many years already the approximate ratio ofthe quantity of red meat produced in the Republic has been 70beef:20 sheep meat:10 pig meat. South Africans are mainlyfresh beef (75 %) and mutton and lamb (98 %) consumers. Inthe case of pig meat almost 70 % is being processed intobacon and ham and other manufactured products. Red meatcomprises 63,5 % and white meat 36,5 % (during 1987/88) ofthe total amount of meat consumed in the country (Dept AgricEcon Market., 1990). Only a small quantity of meat is annuallyexported from South Africa.

A voluntary grading system was instituted in South Africa in1936 and in 1939 this became mandatory in certain parts ofthe country. In 1956 an auction-on-the-hook method ofmarketing was initiated, in which was incorporated a grade-linked minimum producer's price, This system is presently stillin operation. In order to operate such a system of minimumguarantee prices, the producers pay a carcass levy into astabilization fund. The Meat Board may then draw from thisfund in order to buy in surplus carcasses which are unable torealise more than the minimum guarantee price. Thesecarcasses are then presented to the market once the demandjustifies it. The producer is then being paid the minimumguarantee price and the loss incurred, if any, is carried by thestabilization fund. As a result of this situation, as outlinedabove, the grading system in South Africa became distinctlyproducer-orientated. During the period 1936 to 1978 majorchanges in the grading system were introduced on 22occasions to comply with the ever changing needs anddemands of producers but also to recognize changes inmarket trends. In the past two decades market forces,especially consumer demands, started exerting pressure on agrading system originally designed primarily for the benefit ofthe producer. From the initial stages of grading carcasses inthis country, most of the important carcass and meat qualityparameters were considered when a specific grade wasallocated. These characteristics contributed in acomplementary fashion and no consistent attempt was made

in grouping only carcasses with similar traits together. Hence�carcass quality� was described by a combination of factorssuch as conformation and fat cover of the carcasses ofanimals of a certain age (number of permanent incisor teeth)and sex, all being of major importance in the grading system.Varying combinations of these factors in a grade did not,however, clearly indicate to the consumer the physical,compositional and sensory characteristics of the meat.

On several occasions since 1965 the Minister of Agriculture'sAdvisory Committee on Beef, Mutton and Goat MeatProduction requested the ADSRI to perform a scientificinvestigation into the effectiveness of the then existing gradingsystem. This investigation regarding beef carcassescommenced in 1975, was completed in July 1979 and itsresults culminated in the publication, of a new set ofclassification as well as grading regulations for red meat inSouth Africa in the Government Gazette of June 30th 1981.Only once before, since the inception of the carcass gradingsystem in 1936 was a study undertaken on a small scale (VanJaarsveld, 1949), to assess the validity and effectiveness ofthe grading system. At that time large and extremely fatcarcasses were grouped together in the target grades - thesewere often produced from animals with 6 or more permanentincisor teeth. In the A age group, carcasses of the Supergrade had a fat content of 32,1 % (Table 1) as compared tothe present level (since 1981) of 18,0 %. During the nineteenfourties the tractor was being introduced into the grainproducing areas of the country at an ever increasing rate,resulting in cattle being slaughtered at younger ages thanduring the pre-second world war era of the draught ox. Sincethe early fiftees of this century, however, production andmarketing systems and trends as well as consumers' trendsand demands, have been changing continuously. Changesmade to the grading system were mostly to suit the changingneeds and trends of the producers and their systems, andwere not necessarily based on experimental findings regardingmeat yield and sensory characteristics of the product.



62

CARCASS GRADE CARCASS FAT (%) MEAT FAT (%)1949 1972 1981 1949 1972 1981

Super A 32,1 24,0 18,0 37,8 28,2 21,2Prime A 25,8 22,0 - 30,4 25,9 -1 A 24,1 19,0 13,2 28,4 22,4 15,52 A 18,8 17,0 24,5 22,1 20,0 28,83 A 9,5 15,0 11,0 11,2 17,6 12,94 A 2,8 11,0 4,0 3,3 12,9 4,71 A = 0-2 permanent incisor teeth: 1949, 1972; A = 0 permanent incisor teeth: 1981

TABLE 1: Carcass and meat composition of A-age1 cattle - 1949 to 1981.

Due to the importance of beef (70 %) in the red meat industryin South Africa, it was decided to investigate the beef gradingsystem first. The main objectives stipulated in the study were:

1. To describe objectively a �typical� carcass which is foundin each grade

2. To evaluate the carcass meat yield and quality of the meatof these identified carcasses

3. To ascertain, using the carcass and meat traits thus deter-mined, whether the existing grading system complies withthe needs of producers, middle men and consumers alikeand

4. If deemed necessary, to develop a new system of classifi-cation and/or grading that would accommodate the re-quirements of all sectors of the South African meatindustry.

SURVEY: BEEF CARCASSES

As a first step towards testing the effectiveness of the 1972-regulations a survey was undertaken of 1 542 beef carcasses(Klingbiel, 1984). These carcasses were selected according tomass frequency within grade and age class found on thelargest carcass auction in South Africa (Johannesburg) wheremore than 1 600 cattle are slaughtered daily. At that time,carcasses were graded into six grades: Super, Prime, 1, 2, 3and 4 and into four age categories: A (0-2 permanent incisorteeth), B (3-6 permanent incisor teeth) and C (7-8 permanentincisor teeth) and C (older than 5 years). Only A-agecarcasses were grouped in Super and B ages in two groups inPrime. Fat cover or �finish�, conformation or �fleshing� and sexwere used in a complementary fashion when assigning aparticular grade to a carcass. Terminology used for �finish�was: proper (5), good (4), fairly good (3), fair (2) and poor (1).In the case of �fleshing� the terminology was: very good (5),good (4), fairly good (3), fair (2) and poor (1). None of theseclasses were quantified and carcasses were judged visually.The number of permanent incisor teeth of each animal werecounted before the head was removed and the sex of theanimal was noted. Up to three combinations of �fleshing�(conformation) and �finish� (fat cover) could be found withingrade, within age and within sex. Bulls were graded separatelyfrom cows and steers and heifers were placed in a third group.

Of each of the carcasses included in the survey the grade/ageclass was noted, as well as the carcass mass, carcassthickness (kg/cm carcass length), fat thickness (5 cm off thecarcass midline at the 10th thoracic vertebra of the coldunquartered carcass) and visual fat cover (scoring range of 1to 4). In the official grading system as well as in this survey,carcasses were graded by the inspectors of the Division of

Agricultural Product Standards within the Department ofAgricultural Economics and Marketing. Inspectors were alsorequested to grade carcasses into thirds of a grade namelySuper+, Super and Super-. In all the age categories adecrease was observed in the mass (205 to 88 kg)conformation (2,85 to 1,38 kg/cm), as well as the fat thickness(3,8 to 0,3 mm) of carcasses of decreasing grade (Table 2 to4). Within grade, however, with an increase in age an increasewas observed in the values for carcass mass, conformationand fat thickness, even though conformation and carcass fatcover of the same grade in each of the three age categorieswere described in identical subjective terms for visualassessment. One of the most significant findings of this surveywas that the variation in all parameters (especiallyconformation and fat thickness), was much greater within agrade of a particular age class, than that observed betweengrades within an age class (Tables 3 and 4). Thereforecarcasses of similar fatness were not successfully groupedtogether in the same grade. Fat thickness of Super carcassesvaried between 1,0 an 8,0 mm and of Prime A carcassesbetween 0 and 9,0 mm. The mean values for these respectivegrades were 3,8 and 3,2 mm - a difference of 7 and 9 mmwithin grades and 0,6 mm between these two grades (Table4). The �finish� of Super carcasses could vary between a scoreof 3 and 5 and that of Prime carcasses between 2 and 4 and�fleshing� scores varying between 4 and 5, and 3 and 5respectively. A further significant finding of this survey,however, was that the inspectors were able to repeatablycorrectly visually assess the fatness of carcasses. They wereable to distinguish three levels of fat cover within a particulargrade - 4,1, 3,7 and 3,3 mm for Super+, Super and Super-respectively (Table 5).

BEEF CARCASS AND MEAT EVALUATION

Results obtained in the survey facilitated the selection of arepresentative sample of heifer and steer carcasses from themost important grades numerically speaking: Super, Prime Aand B; 1 A, B and C; and the grades 2 and 3 which were alsosampled in the three age categories. The four most importantmass groups (50 kg intervals) were sampled in each grade.



63

GRADE n MASS (kg)Minimum Maximum Mean

SUPER 183 87 320 205PRIME A 138 100 293 1901 A 166 81 291 1782 A 127 76 297 1653 A 76 55 242 1214 A 3 71 114 88

TABLE 2: Mass of beef carcasses in the A-agecategory.

One �lean� and one �fat� carcass per mass class was selecteddue to the large variation found within each grade in the datafrom the survey. The mass of the carcass selected torepresent a specific mass class (50 kg to 325 kg - 7 classes),

was within 10 kg of the median of the class. The buttocklength was also not to deviate more than one standarddeviation from the mean of the value for that specific massclass. In this way 76 carcasses were carefully selected,physically dissected, chemically analysed and the meatevaluated physically, chemically as well as by a trainedsensory panel.

The carcass traits used to test for statistical differencesbetween grades are given in Table 6. A general trendobserved in the data was that the grades Super, Prime and 1did not differ significantly but were different from the grades 2and 3 which were not statistically different from each other inmost cases. The first three grades in the A group (Super,Prime and 1) varied in carcass fat content between 17,0 and19,6 % and the figures for the last two grades (2 and 3) were9,4 and 10,0 %. The same trend was observed forsubcutaneous fat: 5,3 to 6,6 % and 2,5 to 3,23 % respectively;for meat yield: 77,0 to 77,7 % and 79,8 to 80,1 %. Forexpensive meat, the figures were 43,0 to 43,8 % and 44,4 to45,2 % respectively. Once again, as was the case in thesurvey, a very large variation in carcass traits was found withineach of the grades tested. In terms of carcass fatness, as anexample, with the Prime A carcasses the mean values forcarcass fat thickness (mm), fat content (%) and subcutaneousfat (%) were 5,5; 19,6 and 6,6 with the ranges of each ofthese traits respectively being 0,7 to 8,5 mm; 14,8 to 25,1 and4,9 to 9,5 %. Age differences (A, B and C) for the variouscarcass characteristics evaluated, were not statisticallysignificantly different.

Data given in Table 7 indicate the influence of age of animalon meat characteristics. The solubility of collagen in theM. longissimus lumborum was higher in the A age group in allgrades than that found in B and C group animals namely 21,3to 22,6 % for A age and 16,2 to 18,3 % for B age animals.Values for the C age animals (16,4 and 16,8 %) were notstatistically different from those in the B age group. Thedeclining age trend in muscle collagen solubility, was however,observed in all the data presented. A similar kind of trend asthat found for collagen solubility, was established in the panelscore for tenderness. The coefficient of variation for collagensolubility values varied between 5 and 24 %. However, in thecase of the tenderness score it varied between 16 and 38 %.The South African beef carcass is relatively small e.g. 220 kgfor all carcasses marketed in controlled areas (65 %) during1989 (Meat Board 1990). The variation within and betweengrades in carcass mass is very wide. The meat hygieneregulations stipulate that all red meat carcasses marketed incontrolled areas are to be chilled at chill room temperatures of0 °C, with an air velocity of 0,75 m/sec and relative humidity of95 %. Under these conditions, small, lean carcasses chill morerapidly than larger fatter carcasses and undergo more severecold shortening the faster the chilling rate and the smaller and



64

GRADE n kg/cm CARCASS LENGTHMINIMUM MAXIMUM MEAN

Super 183 1,42 4,07 2,85Prime A 138 1,58 3,60 2,581 A 166 1,36 3,42 2,412 A 127 1,29 3,96 2,263 A 76 0,75 3,02 1,754 A 3 1,12 1,73 1,38

TABLE 3: Conformation of beef carcasses in the A-agecategory

GRADE n FAT THICKNESS (mm)Minimum Maximum Mean

Super 183 1,0 8,0 3,8Prime A 138 0,0 9,0 3,21 A 166 0,0 9,0 2,72 A 127 0,0 8,0 2,13 A 76 0,0 4,0 0,94 A 3 0,0 1,0 0,3

TABLE 4: Fat thickness (5 cm off midline at 10th rib) ofchilled beef carcasses in the A-age category.

GRADE n FAT THICKNESS (mm)Minimum Maximum Mean

Super+ 89 1,0 8,0 4,1Super 82 1,0 8,0 3,7Super- 12 2,0 5,0 3,3Prime A+ 36 1,0 7,0 3,6Prime A 82 1,0 9,0 3,2Prime A- 20 0,0 6,0 3,01 A+ 27 0,5 8,0 3,11 A 113 0,0 9,0 2,61 A- 26 0,0 7,0 2,8

TABLE 5: Fat thickness (5 cm off midline at 10th rib ofcarcasses in the A-age category graded inone third of a grade.

leaner the carcasses; hence the greater the extent of coldshortening. Due to these varying chilling rate conditions withina grade, varying degrees of cold shortening will naturallyinfluence the tenderness of beef to a marked extent. Noelectrical stimulation was applied in controlled area abattoirswhen this research was done, hence small between-gradedifferences in tenderness, with high coefficients of variation,were found. The age-linked biological influence of musclecollagen solubility on tenderness, was, however, quite clearfrom the results of this study. These carcasses were regardedas being a representative sample of commercial carcassesbeing presented on the market.

The muscle pigment content (µg Fe/g muscle) was determinedin the M. longissimus lumborum (Tables 7 & 8). It was foundthat the pigment-Fe content was statistically significantly higherin B and C age animals than in A age animals. Differencesbetween B and C age animals were not statistically significant,but C age values were of a higher order than B age values(A = 56,7; B = 66,2 and C = 71,5 µg Fe/g).

DEVELOPMENT OF A CLASSIFICATION

APPROACH

During the selection of carcasses the �finish� and �fleshing� ofeach were judged on a 15 point scale by the graders. Thesimple correlation coefficient between �finish� andsubcutaneous fat percentage was r = 0,82 (Table 9), �finish�and meat percentage r = -0,70; �finish� and bone percentage r= -0,62 and �finish� and kidney knob percentage r = 0,60.When correlations between �fleshing� and carcass yield traitswere calculated (Table 10) they were found to be r = 0,44 forsubcutaneous fat, r = -0,17 for meat, r = -0,64 for bone and r =0,32 for kidney knob respectively. Using path coefficientanalyses it was found that �finish� explained 79,8 % of thevariation in meat yield, versus the 11,1 % explained by�fleshing�. Finish could, therefore, be considered a moreaccurate parameter of meat yield than fleshing. These trendsare illustrated in Figures 1 to 3.

Correlations between six fat thickness measurements andsubcutaneous fat percentages were calculated (Table 11).Correlations varied between r = 0,43 and r = 0,74. The lattercorrelation was between the fat thickness taken on the



65

PARAMETER IN AGE GROUP GRADE

Super Prime 1 2 3

FAT THICKNESS (C+D)/2xrange

6,63,0 - 10,0

5,50,7 - 8,5

4,43,0 - 7,0

1,80,0 - 5,0

2,00,0 - 8,6

FAT IN PRIME RIB %xrange

18,313,9 - 23,7

19,614,8 - 25,1

17,011,7 - 25,6

10,07,6 - 12,4

9,45,6 - 14,4

SUBCUTANEOUS FAT %xrange

6,12,8 - 8,8

6,64,5 - 9,5

5,33,0 - 6,8

3,22,4 - 3,8

2,51,4 - 3,5

KIDNEY FAT %xrange

3,01,9 - 5,0

2,82,0 - 3,7

2,62,0 - 4,2

1,81,0 - 2,7

1,81,3 - 3,1

MEAT (-SC FAT) %xrange

77,374,5 - 81,6

77,076,6 - 79,1

77,776,2 - 79,3

80,179,4 - 81,4

79,877,8 - 82,2

BONE %xrange

13,612,5 - 14,1

13,612,5 - 14,2

14,413,1 - 15,7

14,813,8 - 15,9

16,014,2 - 17,8

EXPENSIVE MEAT %xrange

43,.642,5 - 44,3

43,041,4 - 44,0

43,841,2 - 45,5

45,244,5 - 46,8

44,443,2 - 46,3

TABLE 6: Carcass characteristics of A-age beef carcasses in the different grade and age classes (n = 76 ) in total sampleof A, B and C-age groups).

unquartered cold carcass 50 mm from the medial plane of theback bone, over the tenth rib. This value was lower, however,than the correlation of r = 0,82 (Table 12) between visualassessment of �finish� on a 15 point scale (r = 0,76 on a 5point scale) with subcutaneous fat percentage. Visualassessment of finish by graders was therefore considered tobe a more accurate parameter of the subcutaneous fat than asingle fat thickness measurement.

DEVELOPMENT OF NEW GRADING

REGULATIONS

The results of this research were compiled in a reportsubmitted to different committees who evaluated it and therebycontributed to the formulation of the new regulations during theperiod July 1979 to May 1981.

From the results presented in the research reportrecommending a classification system, as well as the needs ofindustry to develop a grading system, a system was thendeveloped stratifying carcasses in order of excellence basedon the principles of a classification approach. This system wasimplemented on 1 July 1981. A concise summary of thissystem is outlined in Table 13. Conformation is given in fiveclasses: 1 - emaciated; 2 - flat; 3 - medium; 4 - round; 5 - very



66

PARAMETER IN AGE GROUP GRADESUPER PRIME 1 2 3

Fat in M. longissimus lumborum (%)A 1,0 1,3 1,0 0,9 0,8B - 1,6 2,7 1,3 0,6C - - 1,7 1,1 -

Tenderness of M. longissimus lumborum (1 - 5)A 3,2 3,4 3,0 3,7 3,1B - 3,1 3,1 3,2 2,6C - - 2,5 2,7

Collagen solubility M. longissimus lumborum (%)A 22,6 21,4 21,7 21,3 21,3B - 18,3 16,9 17,8 16,2C - - 16,9 16,4 -

Muscle pigment M. longissimus lumborum (µgFe/g)A 47,7 54,3 48,2 63,0 60,6B - 67,5 71,4 58,2 66,8C - - 75,2 67,8

TABLE 7: Meat characteristics of beef carcasses in the different grade and age classes (n = 76).

MEAT TRAITS AGE GROUPA B C

Fat in M. longissimus lumborum % 1,0 1,5 1,4Tenderness score of M. longissimuslumborum (1-5)1

3,3 3,0 2,6

Collagen solubility of M. longissimuslumborum (%)

21,6 17,3 16,6

Muscle pigment of M. longissimuslumborum (µgFe/g)

56,7 66,2 71,5

1 5: Very tender; 1: Very tough

TABLE 8: Summary of meat significantly differentbetween age groups A:B and A:C.

CARCASS YIELD (y) r y = a + bxSubcutaneous fat % 0,82 y = 0,99 + 0,56 xMeat (less SC fat)1 % -0,70 y = 81,52 - 0,45 xBone % -0,62 y = 16,41 - 0,28 xKidney knob % 0,60 y = 1,08 + 0,18 x1 SC: Subcutaneous fat

TABLE 9: Linear regression analyses of carcass �finish�(x), (1-15) and carcass yield traits (y) (n=76).

round. Carcass mass/carcass length (kg/cm) ranges are givenas guideline norms alongside the codes for conformationclasses and were instituted to improve the understandingthereof. The same principle of description and fat thicknessguidelines was applied to the six fat classes. Within an ageclass, different grade names are allocated to carcasses ofcertain fatness classes and these names are arranged in atypical grading structure. In the grade names the letters A, Band C indicate the specific age classes, and terms like SuperA, Prime B and Top C denote the carcasses with fat codes 3and 4 within the three respective age classes. The sameprinciples are applied to carcasses with the remaining fatcodes.



67

FIGURE 2: The influence of carcass finish and fleshing on meat (less SC fat) yield percentage (n = 76)

FIGURE 1: The influence of carcass finish and fleshing on subcutaneous fat percentage (n = 76)

CARCASS YIELD (y) r y = a + bxSubcutaneous fat % 0,44 y = 1,17 + 0,44 xMeat (less SC fat)1 % -0,17 y = 79,64 - 0,16 xBone % -0,64 y = 18,03 - 0,42 xKidney knob % 0,32 y = 1,15 + 0,14 x1 SC: Subcutaneous fat

TABLE 10: Linear regression analysis of carcass fleshing(x) (1-15) and carcass yield (y)(n=76).



68

FIGURE 3: The influence of carcass finish and fleshing on bone percentage (n = 76)

FAT MEASUREMENT r POSITION1 0,65 On M. biceps femoris

2 0,74 On 10th/11th rib 5cm lateral to carcass midline: unquartered side (Position D)

3 0,62 On shoulder 5 cm lateral to carcass midline

4 0,62 On shoulder 15 cm lateral to carcass midline

5 0,43 On quartered side (Position C): at widest aspect of M. longissimus thoracis

6 0,66 On quartered side (Position D): at 2,5 cm lateral to carcass midline

TABLE 11: Correlation between the percentage subcutaneous fat and various fat thickness (mm) measurements of chilledbeef carcasses.

r REGRESSION1. Subcutaneous fat % (y): Fat No 21(x) 0,74 y = 3,045 + 0,537x2. Meat less subcutaneous fat % (y): Fat No 2(x) -0,61 y = 79,804 - 0,428x3. Bone % (y): Fat No 2(x) -0,57 y = 15,385 - 0,278x4. Kidney and kidney fat % (y): Fat No 2(x) 0,52 y = 1,770 + 0,167x5. Prime rib fat % (y): Fat No 2(x) 0,74 y = 10,027 + 1,518x6. Subcutaneous fat % (y): Prime rib Fat % (x) 0,87 y = 0,145 + 0,312x7. Subcutaneous fat % (y): Fat score: 1-15 (x) 0,82 y = 0,987 + 0,555x8. Meat less subcutaneous fat % (y): Fat score: 1-15 (x) -0,70 y = 81,523 - 0,453x9. Bone % (y): Fat score: 1-15 (x) -0,62 y = 16,413 - 0,282x

10. Kidney and kidney fat % (y): Fat score: 1-15 (x) 0,60 y = 1,082 + 0,179x1 Fat No 2: See Table 11

TABLE 12: Correlation between carcass traits (y) and fat parameters (x) of beef carcasses.

Provision is also made for certain carcasses (irrespective offatness) to be graded from one grade into another. Factorsgiving rise to this situation are flat conformation, carcassdamage, oily fat or excessive kidney fat. Carcasses of young(no permanent incisors) intact males showing prominentdevelopment of secondary male characteristics in theforequarters may be graded from A-age to a B-age class. Inorder to verify the validity of regrouping carcasses of theseyoung bulls (A) to the older age group (B) further experimentalwork was undertaken. Findings of previous researchexperiments indicated that young bull beef was tougher thanthat of steers and female animals of the same age and that

bull carcasses also had less favourable proportions ofexpensive to less expensive meat. In the South Africanapproach it was argued that young bulls showing prominentdevelopment of the neck and shoulder areas may be sexuallyfurther advanced than bulls showing less of this developmentand that this may adversely effect quantitative and qualitativecarcass and meat traits respectively. Results showed (Table15) that this assumption was indeed, scientifically speaking,correct but that the magnitude of differences were insignificantfrom a practical industry point of view. Hence it wasrecommended that all young bulls be grouped in the A-age



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FATNESS TRAIT GRADE3 (within age-class)

Fat code Description Fat thickness (mm)1 A B C

1 Very lean <1 A3 (Black)4 B3 (Black) C3 (Black)

2 Lean 1 - 3 A1 (Brown) B1 (Blue) C1 (Red)

3 Medium >3 - 5 SUPER A2 PRIME B2 TOP C2

4 Fat >5 - 7 (Blue) (Green) (Red)

5 Moderately overfat >7 - 10 A2 B2 C2

6 Excessively overfat >10 (Brown) (Blue) (Red)

1 Fat thickness measured between the 10th and 11th ribs 50 mm from the median line of the cold unquartered carcass2 Conformation code 3 to 5; other grades 2 to 53 A = No permanent incisor teeth; B = 1-6 teeth; C = More than 6 teeth.4 Grade names are rollermarked on carcasses covering its entire length on both sides, using the colour ink indicated in the Table**** Grade names are rollermarked on carcasses covering its entire length on both sides, using the colour ink indicated in the Table.

TABLE 13: Summary of grading/classification system.

FAT CODE FAT THICKNESS (mm) SUBCUTANEOUS FAT CARCASS FAT %

(DESCRIPTION) MEAN AND (RANGE) % CLASS (GRADE)

1(Very lean)

0,5(<1)

3,3 11,0(11,0)

2(Lean)

2,0(1 - 3)

4,1 13,5(13,5)

3(Medium)

4,0(>3 - 5)

5,2 16,0

4(Fat)

6,0(>5 - 7)

6,3 19,5(3/4 : 18,0)

5(Moderately overfat)

8,5(>7 - 10)

7,6 23,0

6(Excessively overfat)

>10(>10)

8,4 28,0(5/6 : 25,5)

TABLE 14: Fat traits of different classes of beef carcasses.

class. Subsequently this regulation was changed toaccommodate this recommendation.

Grade 4 consists of carcasses with a fatness code 1 andconformation code 1, as well as severely damaged carcasses.Carcasses of different grades are then roller-marked withdifferent grade names in different colours of ink, as indicatedin Table 13.

THE TARGET GRADE

In order to promote the type of meat preferred by consumersof fresh meat in South Africa, the Meat Board has undertakenregular market surveys over the past 20 years. In a country-wide survey of this nature a market research organizationascertained that 72 % of the consumers preferred thin fatcovering of between 3 and 6 mm on beef roasts (MRA, 1970).Pictures of actual size steaks were used. In 1987 an identicalsurvey was conducted in which the percentage of consumers,preferring a fat cover on steaks of 3 to 6 mm, had increased to77 %. These figures were found regarding white consumers.Amongst the Coloured population the figure was 85 %, forAsians 90 % of those consuming beef and for Blacks it was65 %. These measurements closely resembled the mean valueof codes 3 and 4 for fatness i.e. 5,3 mm and 5,9 %subcutaneous fat, and 18 % carcass fat. These values,indicating the South African consumer's preference, happenedto coincide with the stage of protein maturity (Reid et al.,1955) of the fat free muscles of young growing animals, i.e.,22 % muscle protein, indicating an optimal stage of proteingrowth in the muscles of meat producing animals. It wasdecided, therefore, to use the median value of fat thickness ofthe 3 and 4 fat codes (approximately 5 mm) for the targetgrade of all the age groups, i.e., A, B and C. The group leanerthan codes 3 and 4, i.e., code 2 (1-3 mm) is designated grade1, the overfat group with fat codes 5 and 6 (7 mm) as grade 2;

and the extremely lean carcasses, fat code 1 (<1 mm) asgrade 3, in all age groups. The target A-age carcasses aremarked Super A, B-age carcasses, Prime B and C-agecarcasses Top C (Table 13). Of the beef carcasses marketedin controlled areas, 64,9 % are within the A-age, 20,3 % withinthe B-age, 15,1 % within the C-age and 0,4 % as grade 4. Animportant prerequisite for a target grade to comply with theneeds not only of the consumer and meat trader, but also theproducer, would be that it should be possible for the widerange of cattle genotypes in South Africa to be in line with therequirements of such a grade, this means carcasses with asubcutaneous fat covering of the codes 3 and 4 measuringbetween 3,1 and 7 mm between the 10th and 11th thoracicvertebrae 5 cm off carcass midline.

In a long term experiment (Naudé, 1982) in which numerouspurebred and crossbred types of beef cattle of early and latematuring as well as small and large frame sizes werecompared under feedlot conditions and serially slaughtered at210, 340, 380 and 440 kg live mass it was determined atwhich live masses animals would be market ready in terms ofa target grade approach. From the data in Table 16 it can beseen that Afrikaner steers under feedlot conditions would have



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STEERS BULLS BULLS(+)Chuck % 10,0a 11,2b 12,7c

High priced cut % 38,90a 37,80b 36,90cHind quarter % 50,90a 49,50b 48,10cEconomic value(c/kg)

591,50 589,90 589,80

Tenderness (1-6) 3,68 3,45 3,14Shear force(N/25mm dia.)

106,80 119,50 121,30

Flavour (1-6) 4,10 4,17 4,09abc Different superscripts in the same row indicate values signicantiy differentat P<0,05

TABLE 15: Carcass and meat characteristics of steer andbull carcasses (n=30).

BREED TYPE LIVE MASS (kg) CARCASS MASS (kg)3mm SCF 7mm SCF 3mm SCF 7mm SCF

1. Hereford 264 364 150 1802. Afrikaner 260 384 148 2303. Brahman 328 414 198 2504. Bonsmara 342 484 207 3005. Friesland 342 ++ 188 ++6. Simmentaler 384 ++ 230 ++7. Charolais 394 ++ 238 ++8. Hereford x Afr 310 406 185 2459. Brahman x Afr 322 436 194 263

10. Simmentaler x Afr 302 450 180 27511. Gelbvieh x Afr 296 484 175 30012. Limousine x Afr 280 484 162 30013. Chiana x Afr 328 484 198 30014. Charolais x Afr 346 ++ 210 ++15. Blonde'D Acqui

taine x Afr354 ++ 213 ++

16. Normande x Afr 384 ++ 230 ++1 Steers were fed a high concentrate diet from 7 months of age to slaughtermass. No growth promotants and ionophores were administered.

TABLE 16: Live and carcass masses of steers (A-age)1complying with the fat requirements of SuperA grading (3 to 7 mm of subcutaneous fat).

to be slaughtered at live masses between 264 and 364 kg,producing carcasses with masses between 150 and 218 kg. Inthe case of Charolais steers, these figures would be 394 kglive mass minimum (carcass mass 238 kg) and the maximumwas outside the prediction scope of the experiment, i.e. morethan approximately 300 kg carcass mass.

The decision to exclude 2-teeth animals from the A-age andtransfer them to the B-age was based on results mainly fromthe studies by Boccard (1978) and Boccard et al., (1979). Thedividing line for muscle collagen solubility in cattle was foundto be between 16 and 18 months. Tuma et al., (1962),Dunsing (1959) and Simone et al., (1959) all found that anincreased rate of muscle toughening occurred from between18 to 20 months of age. It was therefore attempted toseparate, as far as possible, these young animals with a highmuscle collagen solubility, from the older ones with a highmuscle collagen solubility, from the older ones with a lowercollagen solubility. In order to achieve any kind of agegrouping in practice, the eruption of permanent incisor teeth isused, where, on average, the first pair appears at anapproximate age of 21 months, the second pair at 30 months,the third pair at 40 months and the fourth pair at 56 months.Eruption of the first pair is given by Brown et al., (1960) as 18-24 months, by Kempster et al., (1982) as 22 months, and byseveral other workers as 20,5 to 26,5 - the range being 18 to26,5 months. Afrikaner cattle were found to cut their first pairof teeth between 20,6 and 33,8 months (Steenkamp, 1970)and Brahman cattle between 24 and 28 months (Fourie 1982)of age. Cattle on high, medium and low plane diets cut theirteeth at 23,6; 25,2 and 26,8 months (Steenkamp, 1970)respectively. All these results indicated that cattle cut their firstset of permanent incisor teeth between 18 and 34 months ofage and, in order to group animals with a high degree ofmuscle collagen solubility together, one would have to groupall animals with only temporary incisors separately from therest, which were divided in two groups: 1 to 6 and more than 6permanent incisors.

From a biological point of view, therefore, carcasses with meatof varying potential tenderness were separated into threegroups, especially with a view to marketing tender meat (A-age) in a group distinctly separate from the less tender meat(B- and C-age groups). However, this grouping did notovercome the problem of a large variation in tenderness withinage groups, due to different degrees of cold shorteningresulting in the toughening of muscles. It was clearlydemonstrated by Heinze & Naudé (1986) and Kerens & Visser(1978) that carcass size, carcass fat cover as well as coldroom temperature all had significant effects on the rate ofchilling of the muscles in the carcass. Chilling rate of muscleshad a marked effect on the extent of cold shortening andtoughening of muscles. As previously mentioned all carcassesin South Africa marketed in the controlled areas are chilled at

0 °C; 0,75 m/s air velocity and 95 % relative humidity -conditions ideal for differential chilling rates of the largevariation of carcass sizes and fat coverings within agecategories. A further practical aspect is the fact that it couldtake more than an hour to fill a chiller holding between 250and 350 carcasses and that during this period the temperaturein the cold room could rise with 10 °C to 15 °C. This wouldresult in the first carcasses entering the chiller at a much lowertemperature than the last ones, hence chilling occurring atwidely different rates, resulting in different degrees of coldshortening.

In order to overcome this major obstacle of an unacceptablepotential variation of tenderness within age classes, a widerange of experiments was undertaken on the influence ofelectrical stimulation on the prevention of cold shortening.These were most successful (Naudé, 1980) and the ultimateoutcome of these investigations was that the AbattoirCorporation, who own almost all the abattoirs in the controlledareas, accepted the recommendation to institute high voltage(450 V) electrical stimulation of beef carcasses (8 minutes postmortem for 60 seconds on the bleeding line) at all theirabattoirs at eleven centres on all the slaughter lines. Theymonitor the pH of the M. longissimus thoracis two hours poststunning at regular intervals in order to ensure that the systemis operating satisfactorily in lowering muscle pH to levels below6,0.

A great deal of the within age-group variation in tenderness istherefore eliminated. In this way one has moved closer to theideal in a classification system of grouping carcasses of similarcharacteristics together in homogeneous groups to facilitate acommon language and understanding in the market place.

LONG TERM APPLICATION OF

CLASSIFICATION PRINCIPLES

The classification system now in use in South Africa, which isused as a basis for the present grading system, which in itselfis a marketing tool, is based on scientific findings. Thesefindings have been used to describe carcass and meatcharacteristics of the wide range of carcasses marketed in thecountry. The traits described and classified are (1) fatness -from very lean to excessively overfat; (2) conformation - fromvery flat to very round; (3) age - from very young to very old;(4) internal fat - in three classes; (5) carcass damage - in fourclasses; (6) oily appearance of fat; (7) obvious development ofsecondary male characteristics. Grading has to groupcarcasses in order of excellence in accordance with the needsof the day. Using these ranges of carcass classification criteriain the grading system, a common language which isunderstood by all sectors of the industry has been created.With the full description of each carcass by these criteria onthe sales catalogues every day of the auction, there is no



71

need for buyers to view carcasses before deciding which tobuy anymore. The grade roller-marked carcasses indicatingthe ages and fat classes then move through the wholesale tothe retail trade continuously indicating to the consumer thegrade of the meat, i.e. the saleable yield (leanness) as well asthe intrinsic eating quality (tenderness) of the product.Changes in production, marketing and consumers' trends do,from time to time necessitate adaptations to the particulargrading system employed in a country. As from 1981,adaptations due to changes in consumers' trends can now allbe based upon the principles established in the classificationsystem which, in itself does not have to change with changesin the grading system.

CLASSIFICATION AND GRADING OF LAMB

AND SHEEP CARCASSES

In 1981 when the changed grading system for cattle waspublished in the Government Gazette, the classification andgrading for lamb and sheep carcasses were also altered andpublished simultaneously. By that stage, a survey similar to theone conducted with beef carcasses, had been completed.Using the principles established with the beef investigationregarding age, fatness, conformation, internal fat, carcassdamage, and development of secondary male characteristicsas well as the results of the lamb and mutton carcass surveyand of the market survey on consumers' preferences,classification and grading systems for lamb and muttoncarcasses were developed. In the carcass survey it wasestablished that a fat thickness measurement taken at aposition between the 3rd and 4th lumbar vertebrae 25 mm offthe midline of the carcass, was the most reliable of fivemeasurements taken for estimating the visual fat cover of thecarcass. A classification of similar age groups as in the case ofbeef carcasses (A, B and C), similar fatness classes (1 to 6)as well as conformation classes (1 to 5), were used for lamb(A) and mutton (B and C) carcasses. The guideline values forfatness and conformation were, however, determineddifferently to those used in beef.

CARCASS AND MEAT EVALUATION

The investigation in beef was done with respect to theprevious (1972) grading system, but with lamb and mutton theobjective was to test the validity of the then present (1981)grading regulations which were developed, using the principlesestablished in the beef investigation. These principles were allreaffirmed by the results of the carcass and meat evaluationresearch done on lamb and mutton carcasses (Bruwer, 1984).

AGE

The principle that collagen solubility of muscle is an importantbiological determinant of meat tenderness was described byHeinze, et al., (1986) for several sheep breeds producing meatin South Africa. In general it was found that collagensolubilities of muscles at 1, 4 and 18 months of age wereapproximately 46, 36 and 22 % respectively. A similar trendwas found with commercial carcasses bought on a carcassauction, i.e. 21,2 % for A-age; 20,2 % of B-age and 18,1 % forC-age animals. These differences in collagen solubilities werereflected in differences observed in meat tenderness.

FATNESS AND CONFORMATION

As was the case with beef carcasses, it was found with thelamb and mutton carcasses (Table 17) that visual carcassfatness was the most accurate estimator of subcutaneous fat,meat and bone yield of carcasses. Conformation was found tobe a poor predictor of carcass composition, hence confirmingresults with beef carcasses and supporting the decision thatfatness be used as the main carcass classification parameterand that much less emphasis is placed on conformation as aclassification and grading parameter. The fat thicknessmeasurements used as guidelines for lamb and sheepcarcasses are the following:

1 = <1 mm; 2 = 1-4 mm; 3 = >4-7 mm; 4 = >7-9 mm; 5 = >9-11 mm and 6 = >11 mm.

In Table 18 the carcass composition data are given for threegrades of lamb carcasses with the specific fat code grouping



72

CARCASS TRAITSFAT SCORE

(1-18)CONFORMATION

SCORE(1-15)

CARCASS MASS(kg)

INTERACT CD RSD

Subcutaneous fat % 81,47 0,06 2,15 -8,60 75,08 1,83Lean % 68,38 3,06 0,68 -13,03 59,10 2,05Bone % 57,39 7,85 0,06 16,66 81,96 0,99Total fat % 80,83 0,75 0,44 0,31 82,33 2,73

TABLE 17: Variation in (%) composition of lamb carcasses (n = 40): using path coefficient analysis.

presently being employed. The increase in visual assessmentof carcass fatness was clearly reflected in all the fatnesscharacteristics of carcasses and the decrease in meat yieldtraits such as total meat yield and expensive meat yield - from54,1 % in lean Lamb 1 carcasses, to 49,9 % in fat Lamb 2carcasses. A concomitant increase from 45,9 to 50,1 % in theless expensive meat was found. Fat3 (3/4 lumbar) was usuallyfound to be almost twice as thick as Fat4 (10/11 thoracic) andthe latter measurement is almost the same as the one usedfor beef carcasses.

The median values for fat codes 3 and 4 are 6,5 mm fatthickness (at 3/4 lumbar vertebrae, 25 mm off midline) and22 % carcass fat, both found in carcasses which have reachedprotein maturity of 19,5 % (Bruwer, 1984). In the MRA (1970)survey of South African consumers, it was found that 84 % ofthe respondents preferred lamb loin chops with less than9 mm of fat which in turn, corresponds with Super lamb gradeand leaner. This figure had changed to 88 % (MRA, 1987) forwhite consumers by 1987 and was also 88 % for Coloureds,95 % for Asians and 77 % for Blacks. Of all the carcasses soldon the carcass auctions in controlled areas, 75 % are lambcarcasses, 9 % from B-age and 16 % from C-age animals.Carcass mass for lamb carcasses is an average of 16,1 kg(18,7 for Super lamb; 15,8 for Lamb 1; 19,4 for Lamb 2 and13,4 kg for Lamb 2) (Meat Board, 1989) and for sheepcarcasses 19,1 kg.

FAT TAILED SHEEP

In the arid regions of South Africa several fat tailed sheepbreeds are well adapted to conditions of high temperaturesand low nutritional planes. Some of these breeds, mainly hairytypes carrying very little or no wool, are the Black HeadPersian, Namaqua Afrikaner, Ronderib Afrikaner, Van RooyAfrikaner, Pedi and then the pelt-producing Karakul breed.Presently carcasses of these fat tailed types complying withthe fatness requirements of the target grades and with the fattails left intact on the carcasses are regraded in the fat codegroup nearest to its particular code - i.e. code 3 carcasses ofpotential Super lambs will be graded as Grade 1 (code 2 forfatness) and code 4 carcasses as Grade 2 (code 5 and 6 forfatness) due to the presence of the fat tail. A study of these fattailed carcasses has just been completed and results aregiven in Tables 19 and 20. After removing the fat tail fromthese carcasses it was found that the carcass composition wasalmost the same as was the case for non fat tailed lambcarcasses with the same fatness code. Eat-fat tailed sheepand be roller-marked as Super lamb carcasses.



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CARCASS TRAITS

GRADELAMB 1 SUPER LAMB LAMB 2

Fat code 2 Fat code 3 +4

Fat code 5 +6

Fat score (1-18) 5,8 8,7 13,7Fat3 (3/4 lumbar) (mm) 3,9 7,4 13,1Fat4 (10/11) Thoracic (mm) 1,4 4,2 7,1Subcutaneous fat (%) 6,2 9,2 12,9Meat less subcutaneous fat(%)

78,2 76,5 74,6

Bone (%) 15,6 14,3 12,5Fat (%) 18,3 23,5 30,2Expensive meat (%) 54,1 52,9 49,9Less expensive meat (%) 45,9 47,1 50,1Leg meat (%) 34,0 31,5 30,9Brisket meat (%) 20,8 22,1 27,1Proportion of lamb carcasses(1988)(%)

45,3 32,0 8,3

TABLE 18: Carcass composition of graded lambs.

CARCASS TRAITS GRADELAMB 3 LAMB 1 SUPER

LAMBLAMB 2

Fat code1

Fat code2

Fat code3 + 4

Fat code5 + 6

Subcutaneous fat %-FT (-T)1NFT2

7,194,31

6,925,51

8,608,05

14,7111,05

Meat %FT (-T)NFT

74,2477,41

74,1276,43

73,7874,35

69,2071,91

Bone %FT (-T)NFT

16,3316,85

17,1216,06

15,1814,40

13,9412,44

Kidney + fat %FT (-T)NFT

2,241,53

1,832,08

2,453,25

2,154,62

Muscle %FT (-T)NFT

65,5167,45

68,6366,09

65,2763,25

61,7259,86

Fat %FT (-T)NFT

19,5915,43

14,3617,51

20,4521,93

25,0727,15

Expensive cuts %FT (-T)NFT

53,9953,37

55,9353,29

55,7952,30

53,5949,23

Leg meat %FT (-T)NFT

33,9234,03

34,3733,96

34,8831,52

32,2330,89

1 FT(-T) : Fat tailed carcasses with tails removed2 NFT : Non fat tailed carcasses

TABLE 19: Carcass composition of lamb carcasses.

FUTURE DEVELOPMENTS

Scientifically based grading and classification specifications stillhave to be developed for calf and goat carcasses. Theapplication of objective measuring of fat and musclethicknesses in sheep and goat carcasses, using the Hennessygrading probe, is to be investigated soon. This procedure hasjust been completed successfully on pig carcasses.

CONCLUSIONS

The main objective of a carcass classification and gradingsystem is to accommodate the needs, preferences anddemands of all sectors of the red meat industry and thesesectors include those of the producer, middle man andconsumer. The final product should be presented to theconsumer in such a way that the quantitative and qualitativetraits of the product are clearly defined for each of the classesand/or grades of the marketing system. A consistent qualityand composition of the product will enhance consumers'confidence, promote sales and turnover and eventuallydiminish price without a loss of income to the producer andmiddle man. If the traits employed in the system are based onscientific fact and can be demonstrated as being of benefit tothe consumer, a situation of mutual trust in the marketingchain is established - a trust which is of long-term benefit tothe entire industry.

ACKNOWLEDGEMENTS

I would like to acknowledge the contributions of many peopleover many years in establishing this very powerful tool of ascientifically based grading system for the South African meatindustry. I would like to single out two of my colleagues, Dr J FG Klingbiel and Mr G G Bruwer, for their dedication in theexecution and successful completion of these two majorresearch projects on beef, and mutton and lamb carcassesrespectively. I would also like to sincerely thank Mrs WaldaBok for preparing the visual aids and Mrs Annette Honeybornefor typing the script.

REFERENCES

BOCCARD, R.L., 1978. Development of connective tissue andits characteristics. In: Patterns of growth and developmentin cattle. Ed. H. de Boer & J. Martin. The Hague: MartinusNijhoff.

BOCCARD, R.L., NAUDÉ, R.T., CRONJÉ, D.E., SMIT, M.C.,VENTER, H.J. & ROSSOUW, E.J., 1979. The influence ofage , sex and breed o f ca t t l e on the i r musc lecharacteristics. Meat Sci. 3, 261-280.

BROWN, W.A.B., CHRISTOFFERSON, P.V., MASSLOW, M. &WEISS, M.B., 1960. Post natal tooth development in cattle.Amer. J. Vet. Res. 21, 7-34.

BRUWER, G.G., 1984. Objective evaluation of the carcassgrading system for lambs and sheep in the R.S.A. MSc(Agric) Thesis, Univ. Stellenbosch.

DEPARTMENT OF AGRICULTURAL ECONOMICS ANDMARKETING, 1986. Abstract of agricultural statistics.Directorate agricultural economic trends - 1986.

DUNSING, M., 1959. Visual and eating preferences of aconsumer household panel for beef from animals ofdifferent age. Fd Technol. 13, 332-336.

FOURIE, C., 1982. That little extra helps. Farmers Weekly,Mobeni, 10th Dec. 1982, 14-16.

HEINZE, P.H. & NAUDÉ, R.T., 1986. Relationship of chillingrate, carcass size and beef tenderness. Proc. 32nd Eur.Meet. Meat Res. Work. Ghent, Belgium 1986.

HEINZE, P.H., NAUDÉ, R.T., SMITH, M.C. & BOCCARD, R.L.,1986. Collagen characteristics of six sheep and goatmuscles. Proc. 32nd Eur. Meet. Meat Res. Work. Ghent,Belgium 1986.

KEMPSTER, A.J., CUTHBERTSON, A. & HARRINGTON, G.,1982. Carcass evaluation in livestock breeding, productionand marketing. Granada, London.

KERENS, G. & VISSER, C.J., 1978. Environmentalrequirements during beef carcass chilling. CSIR Report ME1597.

KLINGBIEL, J.F.G., 1984. Development of a grading system forbeef carcasses. DSc (Agric) Thesis, Univ. Pretoria.

MARKET RESEARCH AFRICA, 1970. Presentation report ona meat usage and advertising survey. Confidential reportsubmitted to the Meat Board.

MARKET RESEARCH AFRICA, 1987. All race meat usageand attitude study. Conficential management reportsubmitted to the Meat Board.



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PARAMETER LAMB A MUTTON B MUTTON CFT NFT FT NFT FT NFT

Tenderness 3,70 3,69 3,35 3,42 3,00 2,66Juiciness 3,71 3,65 3,42 3,42 3,07 3,05Flavour 3,50 3,51 3,77 3,57 3,29 3,37Residue 3,99 4,32 3,70 4,33 3,45 3,755 = Highest preference; 1 = Lowest preference

TABLE 20: Sensory evaluation of lamb and mutton.

MEAT BOARD, 1984. Annual report 1983/84.NAUDÉ, R.T., 1980. Electrical stimulation improves meat

tenderness. Meat Board Focus, Nov. 1980, 4-12.NAUDÉ, R.T., 1982. Influence of the new grading system on

beef production. Simmentaler, 7, 6-15.REID, J.T., WELLINGTON, G.H. & DUNN, H.O., 1955. Some

relationships among the major chemical components of thebovine body and their appl icat ion to nutr i t ionalinvestigations. J. Dairy Sci. 30, 1344-1359.

SIMONE, M., CARROLL, F. & CHICHESTER, C.D., 1959.Differences in eating quality factors of beef from 18- and30-month steers. Fd. Technol. 13, 337-340.

STEENKAMP, J.D.G., 1970. The effect of breed and nutritionalplane on the chronology of teeth eruption in cattle. Rhod. J.Agric. Res. 8, 3-13.

TUMA, H.J., HENDRICKSON, R.L., STEPHENS, D.F. &MOORE, R., 1962. Influence of marbling and animal ageon factors associated with beef quality. J. Anim. Sci. 21,848-851.



75

76

N O T E S

THE APPLICATION OF ANABOLIC GROWTH

PROMOTERS FOR SHEEP UNDER INTENSIVE

FEEDLOT CONDITIONS

P.E. STRYDOM, J.F. DE BRUYN, R.T. NAUDÉ, G.E. KRUGER & S.M. VAN HEERDEN


INTRODUCTION

In South Africa the sensitive balance between a negative andpositive profit margin in the sheep feedlot industry urges thefeedlot manager to make as much use as possible of variousproduction aids. This sensitive balance can largely be ascribedto the short feeding period which is the direct result of atraditionally high average purchase mass of 28 kg (Table 1) forfeedlot sheep and the relatively low slaughter mass in order tomeet the grading regulations for an optimum carcass grade. Inrecent years this has become increasingly important due to theconsumer's demand for leaner meat and the consequentproduction of younger animals and smaller carcasses. Thelatter phenomenon might result in a shortage of red meat, andparticularly lamb, if it is not counteracted with the use ofavailable production technology. It is therefore very importantto exploit all the possible production aids in order to attain ahigher profit by manipulating the growth process. In thisregard, anabolic growth promoters could be a most effectiveshort term production aid when compared to genotype, sex,feeding regime and live mass at entering the feedlot, whichcan mostly be implemented over a longer period of time.

The question may, however, be asked whether there is a needfor a higher production of lamb in South Africa. The per capitaconsumption of mutton and lamb was 5,1 kg in 1988 (Table 2).By the turn of the century it is estimated that the humanpopulation in South Africa will be in the order of 36,7 millioncompared to 29,6 million currently. Due to the influence of theprice and supply of other available meats (red and white) onthe demand for sheepmeat, it is difficult to predict the percapita consumption of this product for the future. However, inthe years to come, it is certain that the protein needs of anadditional 6,8 million people will have to be provided from the



53

PHILLIP STRYDOM is a researcher at the Sub-directorate Animal Physiology and Meat Science atthe Animal and Dairy Science Research Intitute. He received his BSc, BSc (Hons) and MSc degreesfrom the University of Pretoria. He is currently investigating the potential of different anabolic growthpromoters for intensive lamb production in South Africa.

SUBJECT FIGURENumber of commercial feedlots 13Number utilizing anabolic growth promoters 10Average purchase mass of lambs 28 kgAverage feeding period 45 days

TABLE 1: Feedlot survey - 1988/89.

different protein sources of which sheepmeat is but one. Dueto the limited carrying capacity of the natural pastures moremeat will have to be produced from the same flock size (28,5million). Possible solutions, therefore, lie in the intensificationof sheep production by:

a) increasing the the percentage of ewes in the flock by re-ducing the whethers

b) improving the weaning percentage

c) improving general feeding and husbandry practices (Gries-sel, 1975)

d) changing the genetic composition of the national herd and

e) applying modern technology aids.

Statistics pointed out that, between 1985 and 1988, theproduction of Super lamb carcasses of more than 18 kgincreased with 27 % over those below 18 kg (Table 2). Duringthe same period the average auction price of carcasses in thecategory above 18 kg was 3 to 4 cents per kg higher than thatof the category below 18 kg.

According to Singh, Galbraith, Scaife & Hunter (1985) anadditional 2 kg carcass mass per animal was obtained overthe same growth period and in the same grade when ananabolic growth promoter was used. In 1988 75 % (Table 2) ofall the sheepmeat produced in South Africa originated from

lamb carcasses (i.e. A-age group) and approximately 8 % ofthe lambs slaughtered were produced in commercial feedlots(according to a feedlot survey, 1988). Taking these figures intoaccount, the total sheepmeat production can be increased withapproximately 624 000 kg without increasing the flock size,changing the composition of the flock or improving theweaning percentage, but merely by using growth promoters.This additional production could realize an extra R 4,2 millionfor the feedlot industry, while the cost of the implant amountsto between R 24 000 - R 72 000, depending on the kind ofimplant used. With regard to point (e) mentioned above, thepercentage of sheep fattened in the feedlots needs to beincreased far beyond the current 8 %. By so doing, thepressure on the natural pastures will be relieved and byapplying certain growth promoters the average carcass masscan be increased without losing income through lower gradesdue to over fatness (Singh et al., 1985). More meat cantherefore be produced from the same number of sheep in amore cost effective way.

Currently, in South Africa, only zeranol and a combination ofoestradiol benzoate and progesterone are registered under Act36/1947 for use by the lamb producer. Various other implantsare however known to do just as well or even better than theabove-mentioned two when used on cattle (Griffiths, 1982;Mathison & Stobbs, 1983). Many of these growth promotershave in fact been tested on sheep by researchers abroad withvarying results in terms of growth response and productcharacteristics (Quirke & Sheehan, 1981; Singh et al., 1985). Itmust, however, be kept in mind that the marketing systems ofoverseas countries, in terms of the most preferred carcassgrade and associated feeding period, slaughter mass andcarcass fatness differ from that of the South African red meatindustry. Therefore, the ADSRI initiated a project in which thepotential of different anabolic growth promoters wereinvestigated regarding their effect on the performance as wellas on the product characteristics of lambs under South Africanfeedlot conditions (Table 1) in the local grading system.

EXPERIMENTAL PROCEDURES

In August 1989 a trial was conducted with 75 SA MuttonMerino whethers with an average initial live mass of 28 kg.The animals were subjected to five different implant treatmentsand assigned to three different slaughter mass groups asdescribed in Table 3. The animals were fed individually on ahigh-energy diet (Table 4) supplied to them on an ad lib basisand were slaughtered at their respective slaughter masses.Data was analyzed by analysis of variance for a 3 (slaughtermass) x 5 (implant status) factorial arrangement. When asignificant effect due to implant status was observed, meanswere separated by Student's t-test (Snedecor & Cochran,1980). Within this framework of the three slaughter masses, areference point of equal carcass fatness was taken into



54

SUBJECT FIGURECurrent per capita consumption of mutton and lamb (kg) 5,1Current human population (million) 29,6Predicted human population for the year 2000 (million) 36,7Sheep population - 1975 (million) 31,0

1989 (million) 28,6Slaughterings at abattoirs in controlled areas(1988/89)(million)

5,2

Carcasses in A-age group (%) 74,6Carcasses from commercial feedlots (estimated value)(%)

8,0

Super lamb carcasses (%): 1985: <18 kg 67,5>18 kg 32,5

Super lamb carcasses (%): 1988: <18 kg 39,7>18 kg 60,3

TABLE 2: Statistics on the livestock, meat and humanpopulation of the Republic of South Africa(Directorate Agricultural Economic Trends,1990).

consideration in order to determine an optimum slaughtermass for each implant through a regression analysis.According to Bruwer (1984) a carcass fat percentage of 22 %is the point where protein concentration in the fat free muscleof the sheep has reached a maximum and the muscle tissuehas therefore reached �protein maturity�. It is thereforeimportant, from a production efficiency as well as a consumerpoint of view, that the animal should be slaughtered as closeto this point as possible as this is the carcass fat level forcarcasses in the fat code 3 and 4 category of the Super lambgrade which is most preferred by the South African consumer(MRA, 1970, 1987).


Growth response

It is evident from this trial that Z, OP and O (see Table 3) hadbetter growth responses in terms of average daily gain (ADG)and feed conversion ratio (FCR) than C (Table 5). Thesegroups respectively gained mass 36, 22 and 28 % faster thanC up to the 42 kg slaughter mass (P≤0,01) while T gainedmass at a 8 % lower rate than C. The OP and O groupsmaintained this performance up to the 47 kg slaughter massbut the advantage of the Z-group was reduced to only 23 %

over C for this growth period (up to 47 kg), compared to a 45% advantage of OP and O and 17 % of T. With regard to feedconversion ratio (FCR), the pattern was the same as theabove. This indicated that Z had reached the optimumslaughter point in terms of growth response over the lattergrowth period (42 - 47 kg), which was in fact confirmed by thecarcass fat (Table 6). In contrast to the current results, Schild,Riet-Correa, Mendez & Ribeiro (1982) reported a 58 %improvement in ADG for whethers implanted with zeranol,although the implants were repeated four times with threemonth intervals (i.e. 12 month growth period). Incorrespondence with our findings, Quirke & Sheehan (1981)reported that oestradiol benzoate + progesterone as well astrenbolone acetate (TBA) combined with the latter gave bettergrowth results than zeranol. In their experiments TBAimplanted whethers showed no significant improvement inADG, which corresponds with the current results. However,Sinnett-Smith, Dumelow & Buttery (1983) reported a 46 % and20 % improvement in ADG and FCR for TBA implanted ewes.

Carcass quality characteristics

Taking the 22 % reference point into consideration C alreadyreached the optimum slaughter mass before 42 kg live mass(Table 6). Z did not reach the 22 % carcass fat level by 42 kgbut was beyond that point at 47 kg. At the 47 kg slaughtermass OP, T and O still did not reach the 22 % carcass fatlevel. Wilson, Varella-Alvarez, Rugh & Borger (1972) reported



55

CODE TREATMENT SLAUGHTER MASS37 kg 42 kg 47 kg

Z Zeranol (12 mg) 51 5 5OP Oestradiol benzoate (10 mg) +

Progesterone (100 mg)5 5 5

O Oestradiol-17β (24 mg) 5 5 5

T Trenbolone acetate (40 mg) 5 5 5C Control (non-implanted) 5 5 5

1 Number of animals per cell

TABLE 3: Experimental design and material (n = 75).

NUTRIENT VALUEFibre (%) 10,5Crude protein (%) 13,8Metabolizable energy (MJ/kg) 10,6Calcium (%) 0,7Phosphate (%) 0,3

TABLE 4: Composition of the diet.

PARAMETER SLAUGHTER MASS (kg) IMPLANT STATUSC OP Z T E

Average daily gain (g/day):

42 310ab 377bc 422c 286a 398c

47 265a 386b 327ab 311ab 385b

Feed conversion ration (kg feed/kg mass gain)

42 5,92a 4,75b 4,53b 5,76a 4,38b

47 6,42a 4,68b 5,28ab 5,47ab 4,55babc Means in the same row, with different superscripts differ significantly (P<0,05)

TABLE 5: Mean values for the growth response of five implant treatments at 42 and 47 kg masses.

a lower carcass fat content for zeranol implanted whethers atthe same slaughter mass as non-implanted animals but Bass,Jagusch, Jones, Reardon & Day (1984) couldn't find anyconsistent change in carcass composition for zeranol treatedanimals. According to Singh et al., (1985) TBA implantion hadno significant influence on the carcass compostion, which is incontrast with the results of the present study. Unruh (1986)reported a general gain in lean deposition with the use ofzeranol, oestradiol-17β and oestradiol benzoate-progesteronefor steers.

With regard to dissected edible tissue, viz. subcutaneous fatand meat, the carcasses of the O group had obtained 29 %less subcutaneous fat and 3 % more meat at 42 kg live massthan those of the C group. At 47 kg these values were 27 %and 1,5 % respectively. The Z group carcasses on the otherhand had 32 % less subcutaneous fat and 2,5 % more meatthan those of the C group at 42 kg live mass. At 47 kg the Ztreated animals had the same amount of subcutaneous fat and1 % less meat than C and respectively 2 and 2,5 % less meatthan the T and O animals (P<0,05). Although the producer isnot directly imbursed for carcass tissue composition, it isimportant to note the influence of different growth promoterson the change in tissue composition (physiological maturity) atthe different live masses as this influences the carcass gradeand, therefore, the optimum slaughter mass and price realized.

When 22 % carcass fat is substituted in a regression analysisthe predicted slaughter masses for C and Z animals are 43and 44 kg respectively while those of OP, T and O animals areabove 47 kg (Table 6). The exact values can however not bepredicted accurately, probably due to the extrapolation beyondthe 47 kg slaughter point. The corresponding carcass massesfor OP, T and O animals, according to the mean values at47 kg slaughter mass are, therefore, above 24,18, 24,90 and24,24 kg respectively (Table 7). According to predictions, theoptimum carcass masses for C and Z animals are 22,02 and21,67 kg respectively. At an average auction price ofR 6,77/kg for Super lamb carcasses (3rd quarter, 1988,Meatboard, 1989) and an average ration cost of R 0,35/kg thefeed margins for C and Z animals were R 120,83 andR 121,26 respectively while the gross margins (feed marginless purchase price) were R 15,83 and R 16,26 respectively.For OP, T and O animals the feed margins were +R 132,69,+R 133,50 and +R 133,56 respectively and the gross marginswere +R 27,69, +R 28,50 and +R 28,56 respectively. It can bededuced from these figures that the optimum carcass mass forlambs can be increased to the benefit of the producer throughthe application of anabolic growth promoters.

Meat quality characteristics

As the concern of this Institute lies not only with the physiologyof the growth process but also the eating quality of finalproduct viz. meat, an intensive investigation was also



56

PARAMETERIMPLANT STATUS

SLAUGHTER MASS (kg) C OP Z T OCarcass composition:Dissection

Subcutaneous fat (%) 42 10,06 9,60 7,64 9,21 7,8147 10,51 8,79 10,50 9,44 8,25

Meat (%) 42 72,49a 73,47ab 4,42ab 3,59ab 74,81b

47 73,70ab 74,57b 72,91a 74,55b 74,76b

Bone % 42 17,45 16,93 17,94 17,20 17,3847 15,79 16,64 16,60 16,01 16,99

Calculated values1

Total carcass fat (%) 42 23,04a 19,72ab 19,08ab 21,04ab 18,43b

47 25,61a 21,40bc 23,35ab 21,58bc 18,61c

Muscle (%) 42 59,51a 63,06ab 63,99b 61,67ab 64,78b

47 59,45a 62,14ab 60,01a 61,85ab 64,41babc Means in the same row, with different superscripts differ significantly (P<0,05)1 Fat = % ether extract; Muscle = % protein + % moisture + % ash (AOAC, 1985)

TABLE 6: Mean values for the carcass quality characteristics of five implant treatments and two slaughter masses.

performed regarding meat quality characteristics (Table 8). Atrained taste panel found that the meat from the non-implantedanimals (C) was significantly (P<0,05) more tender than that ofthe implanted groups. This was confirmed by the physicalmeasurement for tenderness (shear force), although thesedifferences were non-significant. These findings correspondwith results obtained on steers implanted with zeranol oroestradiol-17β (Calkins, Clanton, Berg & Kinder, 1986). Workdone by Nute & Dransfield (1984), however, showed nosignificant difference attributable to treatment with zeranol orprogesterone + oestradiol-17β on the tenderness of beef.Interesting to note is that meat from the OP and O-groupshave the lowest scores for tenderness while they are superiorin growth response compared to the other implants.Furthermore, animals implanted with TBA, which is a syntheticmale steroid, tend to produce more tender meat than thoseimplanted with various oestrogenic implants. This is in contrastwith the general belief and scientific proof that meat from maleanimals is less tender, mainly due to the effect of the male

steroid on the solubility of the connective tissue, collagen, inthe meat (Boccard, Naudé, Cronje, Smit, Venter & Rossouw,1979; Gerrard, Jones, Aberle, Lemenager, Dikeman & Judge,1987).

The taste panel found the aroma of the meat of the OP groupsignificantly (P<0,05) more intense than that of the C and Ogroups. The scores for meat flavour were significantly lower forthe T group compared to the C group and could possible beascribed to the androgenic qualities of trenbolone acetate.However, according to experimental work done by Field (1971)sex status, and therefore the male steroid (like TBA), had littleeffect on the flavour of sheepmeat. Except for the T group, themeat of the implanted groups was significantly (P<0,05) lessjuicy than that of the C group. When all the aspects of sensoryevaluation are put together, the taste panel found that themeat of C animals was significantly (P<0,05) more acceptablethan that of the implanted animals. Patterson & Salter (1978),in their review, reported that meat from steers treated with



57

PARAMETERIMPLANT STATUS

C OP Z T OOptimum slaughter mass (kg) 43,00 +47,001 44,00 +47,00 +47,00Optimum carcass mass (kg) 22,02 +24,18 21,67 +24,90 +24,24Ration cost (R / kg) 0,35 0,35 0,35 0,35 0,35Auction price for Super lamb carcass (1988)(R/kg) 6,77 6,77 6,77 6,77 6,77Feed margin2 (R) 120,83 +132,69 121,26 +133,50 +133,56Advantage over C (%) +9,20 0,40 +10,50 +10,50Cost of implant (R) ±2,00 ±1,00 ±2,00 ±2,501 Optimum slaughter masses and subsequent carcass masses and feed margins of OP, T and O were beyond the 47 kg slaughter point2 Feed margin = Value of carcass - total ration cost

TABLE 7: Comparison of the feed margins of the five implant treatments with regard to the optimum carcass masses.

PARAMETER IMPLANT STATUSC OP Z T O

Sensory evaluation:Tenderness1 4,71a 4,14b 3,94b 4,15b 3,90b

Aroma2 4,19a 4,58b 4,44ab 4,42ab 4,20a

Flavour1 4,26a 4,00ab 3,93ab 3,64b 3,91ab

Juiciness1 4,35a 3,97bc 3,83c 4,24ab 3,94bc

Overall acceptability1 4,15a 3,78b 3,78b 3,63b 3,77b

Physical evaluation:Shear force resistance (N/12,5 mm core) 37,79 42,24 44,84 40,87 42,77

1 Sensory evaluation score for tenderness, flavour, juiciness and acceptibility: 6 = positive extreme, 1 = negative extreme.2 Sensory evaluation score for aroma: 6 = extremely intense, 1 = least intenseabc Means in the same row, with different superscripts differ significantly (P<0,05)

TABLE 8: Mean values for certain meat quality characteristics of the five implant treatments.

TBA or zeranol showed no consistent differences in eatingquality which was supported by Nute & Dransfield (1984) inthis respect.

Product safety

The primary concern regarding meat from animals exposed toexogenous hormones, is health safety. Safety in this respectcan be met by determining the so-called hormonal no-effectlevel (HNEL) for these hormones (Unruh, 1986). In the presenttrial, TBA and oestradiol-17β levels were determined on meatsamples of the T and O groups, as these are the products thatare not yet approved for sheep. The determination limits forthe analysis was 5 µg/kg (ppb). No measurable amount of anyof the above-mentioned compounds were detected above thedetermination limit, which is also the limit set by the EEC. AJoint FAO/WHO Expert Committee report (1981) stated thatTBA is a trienic steroid which is readily metabolized by theliver and therefore has only weak activity after oraladministration. With regard to oestradiol-17β the committeeagreed that the latter is a natural hormone which gives nocause for concern because the contribution of naturalhormones from meat of implanted animals is so small inrelation to levels in the normal diet (oestradiol in dairy productsand plant oestrogens).

CONCLUSION

In view of the above results and discussion, the feedlotindustry of South Africa can benefit from the use of certainanabolic growth promoters through an increase in the feedmargin. Due to a later onset and/or rate of carcass fatdeposition, a higher and more effective growth rate is obtainedover a longer feeding period subsequently resulting in a higherslaughter mass and higher optimum carcass mass. Togetherwith relatively low feed costs, the extra carcass mass withinthe optimum carcass grade results to a higher feed margin.

In the milieu of greater profits it should always be kept in mindthat the consumer has the last say over the eventual outcomeof any growth manipulating process. Therefore, meat quality interms of tenderness, juiciness, flavour and appearance as wellas the acceptability of relatively larger retail cuts due to anincrease in carcass mass should always be considered in suchresearch programmes.

REFERENCES

ASSOCIATION OF OFFICIAL AGRICULTURAL CHEMISTS,1985. Official methods of analysis, 14th ed. Washington;A.O.A.C.

BOCCARD, R.L., NAUDÉ, R.T., CRONJE, D.E., SMIT, M.C.,VENTER, H.J. & ROSSOUW, E.J., 1979. The influence of

age , sex and breed o f ca t t l e on the i r musc lecharacteristics. Meat Sci. 3, 261.

BRUWER, G.G., 1984. Objective evaluation of the carcassgrading system for lambs and sheep in R.S.A.. MSc-thesis,Univ. Stellenbosch.

CALKINS, C.R., CLANTON, D.C., BERG, T.J. & KINDER, J.E.,1986. Growth, carcass and palatibility traits of intact malesand steers implanted with zeranol or estradiol early andthroughout life. J. Anim. Sci. 62, 625.

DIRECTORATE AGRICULTURAL ECONOMIC TRENDS,1990. Abstract of agricultural statistics. Department ofeconomics and marketing

FIELD, R.A., 1971. Effect of castration on meat quality andquantity. J. Anim. Sci. 32, 849.

GERRARD, D.E., JONES, S.J., ABERLE, E.D., LEMENAGER,R.P., DIKEMAN, M.A. & JUDGE, M.D., 1987. Collagenstability, testosterone secretion and meat tenderness ingrowing bulls and steers. J. Anim. Sci 65, 1236.

GRIESEL, M., 1978. A protein utilization strategy for SouthAfrica. S. Afr. J. Anim. Sci. 9, 119.

GRIFFITHS, T.W., 1982. Effects of trenbolone acetate andresorcylic acid lactone on protein metabolism and growthin steers. Anim. Prod. 34, 309.

MARKET RESEARCH AFRICA, 1970. Presentation report ona meat usage and advertising survey. MRA Report.

MARKET RESEARCH AFRICA, 1987. All race meat useageand attitude study management report. MRA Report.

MATHISON, G.W. & STOBBS, L.A., 1983. Efficacy ofCompudose as a growth promotant implant for growing-finishing steers. Can. J. Anim. Sci. 63, 75.

MEATBOARD, 1989. R.S.A.- Livestock and meat statistics,November, 1989.

NUTE, G.R. & DRANSFIELD, E., 1984. The quality of sirloinfrom zeranol implanted steers. J. Fd Technol. 19, 21.

QUIRKE, J.F. & SHEEHAN, W., 1981. Effect of anabolicsteroids on the performance of hill and lowland lambs. Ir.J. Agric. Res. 20, 125.

PATTERSON, R.L.S. & SALTER, L.J., 1985. Anabolic agentsand maet quality: A review. Meat Sci. 14, 191.

SCHILD, A.L., RIET-CORREA, F., MENDEZ, C.M. & RIBEIRO,N.W., 1982. Efficiency of testosterone and zeranol implantsin the control of ovine posthitis and their effect on weightgains and wool production. Anim. Breed. Abstr. 53, 939.



58

SINGH, S.B., GALBRAITH, H., SCAIFE, J.R. & HUNTER,E.A., 1985. The effect of oestrogenic and androgeniccompounds on growwth and body composition of malecastrate lambs. Proc. Nutr. Soc. 44, 93A.

SNEDECOR, G.W. & COCHRAN, W.G., 1980. Statisticalmethods. The Iowa State University Press Ames, Iowa,U.S.A.

UNRUH, J.A., 1986. Effects of endogenous and exogenousg row th p romo t i ng compounds on ca r casscomposition,meat quality and meat nutritional value. J.Anim. Sci. 62 , 1441.

WORLD HEALTH ORGINIZATION, 1981. Health aspects ofresidues of anabolics in meat. Report of a WHO WorkingGroup, 1981. World Health Organization, Regional Officefor Europe, Copenhagen.



59

60

N O T E S

THE DEVELOPMENT OF A NEW CLASSIFICATION

SYSTEM FOR PIG CARCASSES

G.G. BRUWER*, P.H. HEINZE, I.B. ZONDAGH, A. GEE** & R.T. NAUDÉ

Animal and Dairy Science Research Institute, Private Bag X2, Irene, 1675 Republic of South Africa*Present address: Meat Board, P.O. Box 40051, Arcadia, 0007 Republic of South Africa

** Kanhym (Pty) Ltd, P.O. Box 89, Middelburg, Republic of South Africa

INTRODUCTION

The question arises �Why should there be a grading systemfor pigs?�. According to Allen (1986) grading schemes providea common language for describing important determinants ofquality. Payment to the producer and selling into themarketplace both require an effective grading scheme. In orderto be effective a grading scheme must be unambiguous, easilyunderstood and have the confidence of all parties. It must becapable of being applied with consistency and use factorswhich have a strong relationship with the true value of carcassin the market. Producers who supply carcasses of the qualityrequired by the market are thus rewarded and those who failto do so have an incentive to modify their production methods(Allen, 1986). Kempster, Cuthbertson & Harrington (1982)stated that the evaluation of carcasses is important at allstages of the meat marketing chain from farm through to retail.The processor or retailer has to meet his customer'srequirements in terms of the size, attractiveness andcomposition of cuts or products offered for sale and has toestimate the amount of meat he will be able to sell from eachcarcass. Carcass quality is also of concern to the wholesalerand meat packer who buys from farmers and has to meetretailers' needs; and, not least, to the farmer who, consistent

with farming constraints, should be concerned to matchbreeding stock and production systems to maximise his returnfrom the market by providing the types of carcass in greatestdemand by the meat trade (Kempster, et al., 1982).

During the last couple of years there has been an urgentappeal from the pig industry for a revision of the pig carcassgrading system. The following factors have played a role in thedecision to develop a new classification and grading systemfor pig meat in Europe (Kempster, 1986), and was alsoestablished by Bruwer (1986) in a survey:

- Calls for greater market orientation by producers and in-dustry leaders to meet consumer demands for still leanermeat.

- A greater awareness of the variation in carcass character-istics and the increasing demand of the major multiple re-tailers for consistency of product.

- Changes in the pig breed population with increasing inter-est in the use of specialised sire lines involving musclingbreeds from North America and Continental Europe.



77

GERRIT BRUWER was born in 1957. He matriculated in 1974 and obtained the degrees BSc(Agric) (1979), BSc (Agric) (Hons) (1981) and MSc (Agric) (cum laude)(1984) at the Universityof Stellenbosch. In 1987 he obtained a Diploma in Marketing Management through UNISA.From 1980 he was head of the Carcass Evaluation Section at the ADSRI, Irene. He wasinvolved in different research projects i.e. the development of a carcass evaluation system forfat tailed sheep, the influence of pig genotypes on carcass composition, the secondarydevelopment of bull carcasses and the development of the National lamb carcass competition.From 1987 he was responsible for the research which dealt with a comprehensive studyregarding the development of a new classification system for pig carcasses. Various scientific,semi-scientific and popular articles has been written by him as well as the presentation ofscientific and popular papers at various symposiums. He is currently head of Meat Grading atthe Meat Board.

- Meat quality problems due to slaughtering of boars andthe associated problems.

- Uncertainty which slaughter mass is the most economicalfor the pig industry.

- Unavailability of methods in the industry to detect carcassof poor meat (DFD- and PSE meat) and fat quality (fatsoftness and fat splitting).

- The computer revolution and the development of elec-tronic carcass measurement and data capture systems.

Automatic grading probes are now available which are able tosort carcass according to their lean meat content with asatisfactory degree of accuracy and with a high degree ofobjectivity. Producers will have greater confidence in suchsystems than in the present grading system and this will be ofadvantage to the entire industry. Processors will benefit fromthe automation of grading and data capture systems andimproved sorting of carcass for end use. Consumers wouldthen also be sure of a product that is consistent in quality andavailable at a reasonable price.

THE CURRENT SITUATION IN EUROPE

In the countries of the EEC specific regulations have beenintroduced. The classification of pig carcasses has to be basedon objective measurements that enable prediction of the leanmeat percentage. Before January 1st 1989 the new systemhad to be applied in all member countries. The lean meatpercentage is calculated after dissection of the carcassaccording to the EC-Reference method, which meanscomplete separation of the muscles, including those of thehead, as far as possible by knife. Allowance is given to dissectaccording to a national or institute's standard method if therelation between this standard method and the EC-Referencemethod is known (Walstra, 1989).

The EEC-classification scheme is as follows:

If required class S (≥ 60 %) may be used.

The EEC has layed down certain conditions for a formulawhich will be used for the estimation of the % lean in thecarcass. According to Allen (1986) the estimation has to bebased on a representative sample of at least 120 animals ofthe pig population in a country or in a certain area of acountry. A grading probe will be approved if the residualstandard deviation (RSD) is lower than 2,50 % for lean meatpercentage and the co-efficient of determination (R2) is morethan 0,64 (R2 = co-efficient of determination:amount ofvariation in x explaining y; RSD = residual standard deviation -amount of unexplained variation involved when using a certainx for predicting y). Both these parameters are important.

The accuracy of grading probes

The accuracy of estimates of the lean meat % based onvarious measurements on the carcass is usually expressed asthe residual standard deviation (RSD). The accuracy of probesapproved by the EC-Commission is given in the next table. Inthis table also the measurements on the carcass that areincluded in the various regression formulae are given. Theseparameters are:x1 = cold carcass weightx2 = fat thickness between 3rd and 4th lumbar vertebrae, 8 cmfrom the mid-line (3/4 LV)x3 = fat thickness 3/4 LR, 6 cm (or 6 to 8 cm in FRG) from themid-linex4 = x x1 2

2

2+

x5 = fat thickness LR, 6 cm from the mid-linex6 = muscle thickness 3/4 LRx7 = fat thickness over M. gluteus medius, thinnest place atthe mid-linex8 = thickest width of ham, measured from the backsidex9 = thinnest width of waist measured from the backsidex10 = x

x89

x11 = angle of the rounding of the ham against the horizontalx12 = muscle thickness from anterior edge of M. gluteusmedius to dorsal side of the spinal columnx13 = x7/x12x14 = x12x15 = log x7x16 = x7

x17 = x23

Accuracy, expressed as residual standard deviation (RSD) andR2, of different probes approved by the EEC in variouscountries (Table 2). The measurements on which theestimates are based are given as well (for explanation seetext).



78

LEAN MEAT % CLASS≥ 55 E

50 - 54 U45 - 49 R40 - 44 O< 40 P

According to Walstra (1989) the RSD's between countries maynot be compared as such, because of the use of differentmeasurement parameters. A comparison is only justified whenthe probe measurements are carried out on the same batch ofanimals. However, even then differences may occur and beinterpreted wrong when an already existing regression formulapresent in the equipment had been developed on quitedifferent groups of animals. From the above results it isevident that differences between the various probes are smalland any conclusion regarding the accuracy of a particularprobe as a predictor of percentage meat, must be judgedagainst the background given in the previous paragraph. Anegative result with respect to accuracy does not mean that a

particular instrument will not be chosen for grading of pigs in acountry or area. Other characteristics may be more decisive.Furthermore an important issue for comparing of accuracies isthe sample of animals to be dissected as well as thedissection method itself. Confidence in a new classificationsystem can only be given when realistic data within countriesare obtained based on a good reference method (Walstra,1989). As pointed out above the choice of an instrumentneeds not to be based on the accuracy of the measurement,although very important. Other factors like reliability, ease ofuse, number of repeat measurements, ease to connect tocomputers, efficiency in operation, durability and costs may bemore decisive. Even though the optical probe (Intrascope) is



79

COUNTRY APPROVED BY ECCOM-MISION

USED EXCLUSIVELY AS ANATIONAL SYSTEM

USED EXTENSIVELY USED IN SOME ABATTOIRS

Finland HGP HGP

Sweden HGP HGP

Denmark KSA KSA KSA

Great Britain Intrascope Intrascope

FOM FOM

HGP

Northern Ireland Intrascope Intrascope

Ulster probe Ulster probe2 Ulster probe

Republic of Ireland Intrascope Intrascope

FOM FOM

HGP HGP

The Netherlands HGP HGP HGP

Belgium SKG SKG SKG

France FOM FOM

FRG FOM FOM

SKG SKG

ZP Porkitron ZP

Austria (LSQ) FOM

GDR (QMS) QMS

EQM1

1 According to the producer, SKG is also used in Czechoslovakia, Hungary and the USSR2 Between brackets means: almost exclusively used as a national system.

TABLE 1: The use of grading probes in European countries1

only slightly less accurate in predicting lean meat % from fatthickness measurements, the second generation of gradingprobes seem to be preferred to the former well knowninstrument. They combine muscle depth as an extrameasurement. These probes are connected to electronicdevices. Muscle depth measurements in future may becomemore important due to the trend of breeding animals withhigher degrees of muscularity.

The main advantages therefore claimed for the automatic-recording probes are as follows (Anon, 1986):

a. Improved precision of prediction of carcass composition bythe addition of muscle depth measurement;

b. Possession of these data allowing scope for participants tomatch more closely the variation in raw material with endusage;

c. More accurate description of carcass, allowing premia anddiscounts to operate more effectively and hence giveclearer market requirement signals to producers;

d. The potential for measuring colour and, in turn, possiblePSE (pale, soft, exudative) carcass and

e. Reduced operator fatigue and reduced possibility of errorsin measurements.

THE DEVELOPMENT OF A NEW

CLASSIFICATION AND GRADING SYSTEM

FOR PIG CARCASSES IN THE RSA

The ADSRI at Irene was requested by the Meat Board and theSAAU to investigate the possibility of developing a newclassification and grading system for pig carcasses in the RSA.Developments in Europe regarding evaluation techniques ofpig carcass composition, the criticism of the current gradingsystem by pig producers as well as the meat trade and theperception amongst 62 % of the consumers that pig meat is�too fat�, lead to the early and urgent launching of theinvestigation. For this investigation four crossbred genotypes(SALR, SALW, NPDLR and NPDLW) comprising three sexconditions, i.e. boars, barrows and gilts, slaughtered at fourlive masses, i.e. 53 kg (40 kg carcass mass), 68 kg (50 kg



80

COUNTRY PROBE RSD R2 MEASUREMENTPARAMETER

W-Germany FOM 1,79 0,86 x2, x3, x4SKG II 2,19 0,79 x7, x8, x9, x10, x11ZP 2,45 0,74 x13, x14, x15, x16

The Netherlands HGP2 2,19 0,75 x3, x6Denmark KSA 1,85 0,73 x1, x2, x3, x6, x7Rep. Ireland Intrascope 207 0,67 x3, x7, x17

FOM 2,04 0,68 x3, x6, x17HGP2 2,09 0,66 x3, x6, x17

Belgium SKG II 1,99 0,71 x7, x8, x9, x10, x11Great Britain Intrascope 2,44 0,76 x1, x5

2,31 0,78 x1, x3, x5FOM 2,23 0,80 x3

2,18 0,80 x1, x3, x5, x6HGP2 2,37 0,77 x3, x5, x6

2,37 0,77 x1, x3, x5, x6Northern Ireland Intrascope 1,82 0,74 x1, x5

1,92 0,70 x1, x3, x5Ulster probe 2,00 0,68 x1, x5

1,90 0,70 x1, x3, x51 The data given are from EC-documents

TABLE 2: Formulae used in the different EEC-countries1 (Walstra, 1989).

carcass mass), 87 kg (68 kg carcass mass) and 110 kg (90 kgcarcass mass) and were fed a commercial diet. In total 240pigs were slaughtered, 60 pigs/genotype. Various fat thicknessmeasurements at different positions were taken on the hotcarcass with the Hennessy Grading Probe (HGP) andIntrascope (Figure 1) 45 mm, 60 mm and 80 mm lateral fromthe carcass midline. Carcass length measurements were takenon the cold carcass. After the above measurements wererecorded the right side of each carcass was separated intodifferent cuts (Figure 2). The mass of each cut was recordedand each cut was separated into lean, fat and skin and bone.The mass of each carcass tissue was recorded to determinecarcass and cut composition. Fat and meat qualitymeasurements were taken using different instruments andtechniques, i.e. pH values, Fibre Optic Probe, EEL, FatSoftness Meter, iodine values, refraction index and theHenessy Grading Probe. The belly and leg of the left side ofeach carcass were processed into bacon and restructured hamrespectively while the loin of the left side was used as an

example for fresh meat. The loins, hams and bacons weresubjected to sensory evaluation.


Carcass composition as influenced by

genotype, sex condition and live mass

The influence of genotype

It was found that genotype had a significant influence (P<0,05)on % loin back, % loin belly, % middle back, % middle belly, %subcutaneous fat, % lean, % muscle and % total fat. TheSALR had the highest % loin back, lowest % loin belly, highest% middle back, lowest % middle belly, highest %subcutaneous and total fat and lowest % lean and muscle.The NPDLW was the opposite of the SALR with the SALWand NPDLR intermediate between these two genotypes (Table



81

FIGURE 1: Fat thickness positions measured on thecarcass

FIGURE 2: Dissection technique used on the carcass

3). Results of various researchers (Omtvedt, 1974; Pedersen,1984; McGloughlin, Lynch, Hanrahan & Allan, 1986) showedthat considerable genetic variation occurred regarding carcasscomposition, within as well as between breeds.

As this trial was not designed as a breeding trial noconclusions should be drawn to the effect that the onegenotype is superior to the other. These results are a mereindication and is not representative of the breeds found inSouth Africa. These breeds, however, gave the variation intype that was necessary for the execution of the trial.

The influence of sex condition

Sex condition had a significant influence (P<0,05) on almost allthe parameters except for loin belly. Boars had the lowest %loin back, % middle back, % subcutaneous fat and % total fatand the highest % leg, % shoulder, % middle belly, % leanand % muscle. Gilts were in most cases intermediate while thebarrows produced carcasses with most fat (Table 4).

These results were as expected and the reason for the boarsto be superior regarding the % lean has been welldocumented in literature (Wood & Riley, 1982; Ellis, Smith,Clark & Innes, 1983). Boars are late maturing. Fat willtherefore accumulate at a later stage than with barrows andgilts. The results will also be very interesting to processors indeciding from which sex group they will get the highest yield ofspecific cuts used for certain products.

The influence of live mass

Carcass mass had a significant influence (P<0,05) on all theparameters for carcass and cut composition except for % loin

back and middle belly. Carcasses of the 53 kg live massgroup had the highest % leg, % shoulder, % lean and % bonewith carcasses in the 68 kg, 87 kg and 110 kg live massgroups decreasing amounts in this order, for the parametersmentioned (Table 5). It is quite evident that the early maturingparts, i.e. the % shoulder and % leg were the highest in the 53kg live mass group and the lowest in the 110 kg live massgroup and this is as expected. The % middle back in the 110kg live mass group was the highest of all mass groups andthis is, from a fresh as well as processed meat point of view,most important.



82

PARAMETERGENOTYPES

SALR SALW NPDLR NPDLWLeg % 27,67 27,56 27,74 27,47Loin back % 11,90a 11,81ab 11,56bc 11,40c

Loin belly % 5,30a 5,57a 6,25b 6,53b

Middle back % 16,51a 16,09a 14,78b 15,25b

Middle belly % 10,44a 10,86ab 11,17b 11,19b

Shoulder % 28,18 28,11 28,22 28,45SCF % 22,12a 20,78b 19,97bc 19,13c

Lean % 65,68a 67,08b 68,01c 68,63c

Bone % 10,08ab 10,05ab 9,88a 10,25b

Kidney % 2,12 2,09 2,14 1,99abc Means in the same row with different superscripts differ significantly (P<0,05)

TABLE 3: The influence of genotype on carcass and cut composition.

PARAMETER SEX CONDITIONBOAR BARROW GILT

Leg % 27,84a 27,18b 27,83a

Loin back % 11,03a 11,97b 11,96b

Loin belly % 5,90 5,82 6,00Middle back % 14,91a 16,39b 15,64cMiddle belly % 11,24a 10,79b 10,72b

Shoulder % 29,08a 27,84b 27,84b

SCF % 17,96a 22,61b 20,81c

Lean % 69,32a 65,47b 67,34c

Bone % 10,95a 9,48b 9,81c

Kidney % 1,75a 2,44b 2,04cabc Means in the same row with different superscripts differ significantly(P<0,05)

TABLE 4: The influence of sex condition on carcass andcut composition.

The prediction of carcass composition

Thirty three different measurements at different positions weretaken with the HGP (fat thickness and muscle thickness) andIntrascope. To establish which position will predict carcasscomposition the best, simple regressions were initiallyexecuted between fat as well as muscle thickness andparameters of carcass composition. The % lean is the mostimportant in this case as this should be the basic principle ofany classification system.

In Tables 6, 7 and 8 results are presented for the varioussimple regressions. Only the six positions with the lowestRSD's are presented together with P2 which is the fatmeasurement currently used in the grading of pig carcasses.

The position with the best prediction of

carcass composition

As mentioned before a grading probe and grading system isapproved in the EEC if the RSD is lower than 2,50 and the co-efficient of determination (R2) is more than 0,64. From Table 6it is evident that the position T 2/3-45 is the best single fatthickness measurement for the prediction of the % lean in thecarcass using either the HGP or the Intrascope (Table 7) (RSD= 2,33 and 2,19). The best prediction using a muscle thicknessmeasurement is the position T 5/6-45 (RSD = 3,33). Musclethickness is therefore a much less accurate method for theprediction of % lean in the carcass (R2 = 0,08 in Table 8). Theanatomical region of T 2/3 seems to be quite accurate as thepositions T 2/3-60 and T 2/3-80 are the 4th and 5th most

accurate predictors of % lean in the carcass when measuredby the HGP and T 2/3-60 is the 4th best position whenmeasured by the Intrascope. L 5/6-60 which represents the P2fat thickness measurement is a much less accurate predictorof the % lean in the carcass than other fat thickness positions(RSD = 2,64 and 2,32 respectively for the HGP andIntrascope) (Tables 6 and 7). Although not shown, the T 2/3-45 was also the best predictor of % subcutaneous fat in thecarcass when measured by the HGP and Intrascope (RSD =2,20 and 2,17 respectively). These results are in agreementwith results from Kempster & Evans (1979) who examined therelative precision of lateral measurements along the carcass(cranio-caudally). They found that the precision of probemeasurements showed a regular pattern: moving from themost cranial position (fourth/fifth cervical vertebrae), precisionincreased to the positions in the hind rib region (third/fourthlast rib and last rib) and then declined to the most caudalpositions (fifth/sixth lumbar vertebrae). It therefore seems as ifthe hind rib region has some special predictive value. Resultsin Table 8 further indicate that muscle thickness and carcassmeasurements were poor predictors of % lean in the carcass.It was shown that measurements such as carcass length, hamcircumference, conformation, etc. which have always been



83

PARAMETER LIVE MASS GROUPS (kg)53 68 87 110

Leg % 28,10a 28,02a 27,39b 26,87c

Loin back % 11,77 11,57 11,69 11,65Loin belly % 5,26a 5,87b 6,00b 6,54c

Middle back % 14,98a 15,26a 16,15b 16,30bMiddle belly % 11,00 10,83 10,79 11,02Shoulder % 28,89a 28,44ab 27,96bc 27,61c

SCF % 18,48a 19,34a 21,06b 23,39c

Lean % 68,78a 68,41a 67,17b 64,80c

Bone % 11,08a 10,35b 9,52c 9,23c

Kidney % 1,65a 1,90b 2,25c 2,58dabc Means in the same row with different superscripts differ significantly(P<0,05)

TABLE 5: The influence of live mass on carcass and cutcomposition.

POSITION RSD1 R2

T 2/3 - 45 2,33 0,55T 1/2 - 80 238 0,53L6/T1 - 45 2,38 0,53T 2/3 - 60 2,38 0,53T 2/3 - 80 2,39 0,53T 3/4 - 45 2,39 0,53

P2 2,64 0,391 RSD = Residual Standard Deviation; EEC Regulations - RSD<2,50;

R2>0,64

TABLE 6: Prediction of % lean with the HennessyGrading Probe (HGP) (fat thickness).

POSITION RSD R2

T2/3 - 45 2,19 0,60L6/T1 - 45 2,23 0,59T3/4 - 60 2,24 0,58T2/3 - 60 2,25 0,58T1/2 - 45 2,25 0,58P2 2,32 0,55

TABLE 7: Prediction of % lean with the intrascope.

believed to be accurate predictors of % lean, are actually verypoor predictors of % lean (RSD's = 3,29, 3,32 and 3,19 withR2 values of 0,10, 0,09 and 0,19 respectively). Conformation ispresently an important parameter in the carcass classificationand grading system in South Africa. Various researchers havefound that carcass conformation has virtually no value aspredictor of carcass leanness (Kempster & Evans, 1981;Kempster et al., 1982; Kallweit & Averdunk, 1984). Results ofthis study substantiate these findings and therefore the validityof conformation, as a parameter in the South African gradingsystem, can be questioned.

The use of more than one fat thickness

measurement for the prediction of % lean.

It was found that the addition of one or more fatmeasurements to an initial fat measurement taken in the hindrib region, provided a relatively small improvement in theprecision of carcass lean prediction. The decision to use twoor more fat measurements depends largely on operationalefficiency: if two or more measurements can be taken aseasily as one, the small improvement in efficiency is worthhaving according to Kempster, et al., (1982). When usingstepwise regression analyses, all the fat thicknessmeasurements are pooled, and then only those measurementsare selected, which in combination, yield the best prediction ofcarcass composition. The accuracy of predicting the % leanwith the HGP in the carcass improved from a RSD of 2,33 to2,29 (0,05 %) when using three as compared to one fatthickness measurements (Table 9). The T 2/3- 45 aloneexplained 55 % of the 57 % variation in % lean. The additionaltwo fat thickness measurements contributed only 2 % more indescribing the variation that occurred for % lean. From the

above results it seems that one fat thickness measurementwould be adequate for the prediction of % lean with the HGP.The above argument also holds for the prediction of % leanwith the Intrascope. The accuracy of the RSD increased from2,19 with one fat thickness measurement to 2,06 when usingseven different fat thicknesses (Table 10).

In summary it seems that the position T 2/3-45 is the bestposition for the prediction of % lean as well as subcutaneousfat, and the use of more than one fat thickness to increase theaccuracy of prediction seems unnecessary and alsoimpractical. Stepwise regression results for muscle thicknessesshowed that there is no possibility by which muscle thicknessalone can be used as a predictor of carcass composition(Table 11). The RSD values when using muscle thickness are,in most cases, more than 1 unit higher than with fat thicknessmeasurements. However, it is interesting to note that themuscle thickness measured at T 2/3-45 was selected as thesecond measurement in both cases, for the prediction of% lean through stepwise regression. As the muscle thicknessis automatically measured by the HGP when it measures fatthickness, it seems logical to combine the fat and musclethickness, measured at T 2/3-45, to predict the % lean.Results of this investigation showed that the Intrascope was



84

POSITION RSD R2

T5/6 - 45 3,33 0,08T5/6 - 60 3,36 0,06T4/5 - 60 3,38 0,05T4/5 - 80 3,38 0,05T4/5 - 45 3,40 0,04Warm mass 3,21 0,14Carcass length 3,29 0,10Ham length 3,40 0,04Ham circumference 3,32 0,09Conformation (1-15) 3,12 0,19

TABLE 8: Prediction of % lean with the HGP (musclethickness) and carcass length measurements.

POSITION COEFFICIENT R2 RSDINTERCEPT 75,54T2/3 - 45 -0,42 0,55T1/2 - 80 -0,26 0,56T5/6 - 60 0,13 0,57 2,29

TABLE 9: The prediction of % lean with the HGP (fatthickness) using stepwise regressions.

POSITION COEFFICIENT R2 RSDINTERCEPT 76,39T2/3 - 45 -0,27 0,60L6/T1 - 45 0,22 0,62T3/4 - 80 -0,14 0,63T5/6 - 45 0,14 0,64L1/2 - 80 0,09 0,65L2/3 - 60 -0,10 0,66L1/2 - 60 -0,06 0,66 2,06RSD = 2,19; R2 = 0,60 for one fat thickness

TABLE 10: The prediction of % lean with the intrascopeusing stepwise regression.

somewhat more accurate than the HGP in predicting the% lean and subcutaneous fat in the carcass, when using oneor more fat thickness measurements. As the HGP has theadvantage of measuring muscle thickness simultaneously withfat thickness it may well be that the HGP could produce moreaccurate results than the Intrascope. However, as statedpreviously other factors are in most cases more important thanthe accuracy of a probe, when a probe is selected for agrading system. Fat thickness measurements were also takenon the midline of the carcass, for example midback, shoulderfat thickness, etc. Results are not shown in this report but theirpredictive values were very low. Furthermore their applicationis impractical.

The development of a formula that could be

used in a carcass classification system for

pigs

In the previous sections it was established that the fatthickness measured at position T 2/3-45 is the most accuratepredictor of % lean in the carcass when using the HGP or theIntrascope. The HGP has the additional advantage of alsomeasuring muscle thickness while hot carcass mass is aparameter which is always available and very cost effective touse. The next step was to develop a formula that would beaccurate for any genotype, sex condition and mass group. Todetermine this it is critical that no significant differences existregarding the slope or the intercept of regression lines of fatthickness (x) and lean or fat yield (y) between genotypes, sexconditions and mass groups. If significant differences werefound then it would not be possible to use one general formulaover the whole spectrum of carcasses on the market.

Using advanced statistical procedures, i.e. Harvey's Model 1( ( )y b x xij= + − − − −µ ) the following results emerged:

a. No significant differences were found for slopes or inter-cepts between genotypes and sex conditions, whichmeans that one general formula may be used for any car-cass on the market.

b. Carcass mass did not contribute to the accuracy of pre-dicting the % lean or subcutaneous fat in the carcass.

c. The analysis further showed that the T 2/3-45 fat andmuscle thickness measurements were the parameters tobe used for the HGP and T 2/3-45 fat thickness measure-ment for the Intrascope.

d. In the final analysis the HGP was more accurate than theIntrascope in predicting the % lean and subcutaneous fat.

e. The results of this study compare most favourably withoverseas results as described previously.

The following formulae were developed for the different probesto determine the % lean and subcutaneous fat:

The accuracy and reliability of the formula

developed

To make absolutely certain, 45 carcasses were selected atrandom on the market in the carcass mass range 60-70 kg.Fifteen carcasses of each sex condition group at threedifferent fat thickness ranges, i.e. 12 mm, 16 mm and 22 mmwere studied. These carcass were also dissected according tothe method described previously. The actual % lean wasdetermined through dissection and the predicted % lean by

using the general formula. The purpose of the formula is topredict the actual % lean in the carcass as accurately aspossible. If this is true the slope of the relationship betweenthe actual % lean and predicted % lean must be as close to 1as possible and the intercept as close to 0 as possible. Theresults of this trial were as follows:HGP % Lean vs Dissected % LeanSlope = 0,8656Intercept = 7,4968Intrascope % Lean vs Dissected % LeanSlope = 1,0132Intercept = -2,0913

From a statistical point of view these results confirm thevalidity of the formula as a predictor of % lean.



85

HGP INTRASCOPE% LEAN = 72,5114 - 0,4618V** % LEAN = 74,4367 - 0,4023V

(RSD = 1,23; R2 = 0,71) (RSD = 1,25; R2 = 0,69)

%SCF = 13,5990 + 0,0374S % SCF = 12,0420 +0,4776V

(RSD = 1,15; R2 = 0,79) (RSD = 1,17; R2 = 0,79)

* V = T 2/3-45 (fat thickness)**S = T 2/3-45 (muscle thickness)

POSITION COEFFICIENT R2 RSDINTERCEPT 70,08T5/6 - 45 -0,19 0,08T2/3 - 45 0,12 0,12 3,26RSD = 3,33; R2 = 0,08 for one muscle thickness

TABLE 11: The prediction of % lean with the HGP(muscle thickness) using stepwiseregressions.

Meat and Fat quality characteristics

The influence of genotype

Genotype had a significant influence (P<0,05) on FOP values,the fat softness, fat thickness (T 3/4-60), iodine value andrefraction index. FOP-values could be an indication of PSEcarcass as it works on the principle of light reflectance. Thehigher the value the higher the risk that carcass have PSE.From the results in Table 12 SALR had the highest FOP value(150) and the NPDLW the lowest (142). These results,however, were not supported by the values of pH1. (Thistechnique is currently accepted as the best on linemeasurement to determine PSE). The relationship betweenpH1 and FOP value is -0,3808 (Table 15). This indicates thatthe lower the pH1 value the higher the reflectance value of theFOP. The fat softness, iodine value and refraction index areindicators of fat softness which is important for the processingindustry as this could have a negative effect on the quality oftheir product. Results in Table 12 indicate that NPDLW andNPDLR had the softest fat while the SALR and SALW had thehardest fat (the higher the iodine value, the refraction indexand the lower the fat softness meter value the softer the fat).This is substantiated by results in Table 16 where therelationship between fat softness and iodine value is -0,3250.It seems therefore that the fat softness meter could be usedon line as an indicator of fat softness. Various researchers(Omtvedt, 1974; Monin & Sellier, 1985; Christians, 1981) haveindicated that breed has a major influence on the quality of fat.It is for this reason that crossbreeding could be of importance,in respect of certain advantageous characteristics that couldbe enhanced in the crossbreds.


Sex condition had a significant influence (P<0,05) on all meatand fat quality parameters. It seems that boars (5,59) andbarrows (5,60) had higher pH24 values than gilts (5,54) (Table13). These average values are all however within the normalpH24 range. The fat of boars was significantly softer than wasthe case with gilts and barrows with the latter having thehardest fat (Table 13). Much speculation over this finding isstill found in literature. It is well documented that when pigsare too lean this leads to fat softness. In general, entire malesreach slaughter mass at an earlier age and leaner stage thaneither castrates or females. Thus, the fatty tissue containsmore unsaturated lipids, and also more water. The fat istherefore of a lower quality. Fat separation also occurs morefrequently in boars than gilts at the same carcass mass(Winstanley, 1986). Results of this study were further analysedbecause it was found that the fat thickness of boars wassignificantly less than that of gilts or barrows. For this reason aco-variance analysis was conducted where fat thickness washeld constant. Results of this analysis showed that it was asex condition effect and not a leanness problem causing thefat softness. This is a factor that processors should take intoaccount.


Results in Table 14 indicate that the heavier carcass hadharder fat which was more saturated. The reason is that theslaughter mass of the pig is associated with the age of the pig.Younger pigs deposit more unsaturated lipids, and the fattytissue tends to be softer. However, the older the pig, the moresaturated the lipids that are deposited. These fats are harderand firmer (Winstanley, 1986), and are thus more desirablefrom the viewpoint of the butcher and processor. The



86

PARAMETER GENOTYPESALR SALW NPDLR NPDLW

pH1 electrode 6,22 6,15 6,26 6,19pH24 electrode 5,57 5,57 5,60 5,56FOP 150a 148ab 145bc 142c

EEL: Average 31 31 30 30Fat softness meter 514a 521a 469b 462b

Fat thickness (P2) 2,13 2,04 1,95 1,94Fat thickness (T 3/4) 1,78a 1,71ab 1,56bc 1,50c

Iodine value 62a 65a 74b 74b

Refraction index 1,459a 1,459a 1,460b 1,460babc Means in the same row with different superscripts differ significantly(P<0,05)

TABLE 12: The influence of genotype on meat and fatquality characteristics.

PARAMETER SEX CONDITIONBOAR GILT BARROW

pH1 electrode 6,23 6,12 6,27pH24 electrode 5,59ab 5,54a 5,60b

FOP 144 147 149EEL: Average 31 31 30Fat softness meter 438a 498b 536c

Fat thickness (P2) 1,65a 1,97b 2,41c

Fat thickness (T 3/4) 1,35a 1,58b 1,96cIodine value 76a 68b 64c

Refraction index 1,460a 1,459b 1,459cabc Means in the same row with different superscripts differ significantly(P<0,05)

TABLE 13: The influence of sex condition on meat andfat quality characteristics.

relationship between the HGP reflectance value, T 2/3-45 andpH1 (R = -0,3547) (Table 15), is promising as an indicator ofPSE. With the development and research on the HGP which isstill continuing in order to identify PSE carcass moreaccurately, it is claimed that the new HGP-4 Grading Probewill be more sensitive to changes in colour of meat than is theHGP-2 probe, with which this research was undertaken.Interest in assessing meat quality in pig carcasses on theslaughter-line has increased during recent years. Methodsused to assess meat quality is panel scores, reflectance (EEL),fibre optic probe (FOP), pH and Kappillarvolumeter (Somers,Tarrant & Sherrington, 1985). In hot carcasses, the fiber opticprobe (FOP value 45 min post mortem) was superior to thepH1 value for predicting panel score (r = 0,76 and -0,53respectively) and reflectance (r = 0,80 and -0,60) whereas pH1was better than FOP for predicting drip loss (r = -0,65 and0,55). Somers et al. (1985) suggest that the FOP, is a moreuseful predictive measurement for meat quality than pH1 (45min. post mortem). Correlations between different fat softnessindicators as well as between fat thickness and fat softnessare given in Table 16. Leanness was associated with soft fat.

Sensory evaluation of bacons and loins

Influence of genotype

Genotype significantly (P<0,05) influenced odour, texture andjuiciness. The bacon odour of SALR and NPDLW was morepreferred by the taste panel than the odour of the other twogenotypes (Table 17). Although not significantly, the SALR andNPDLW attained higher taste panel scores also for generalacceptability. Genotype significantly (P<0,05) influenced all the

parameters that were evaluated on the loins. The NPDLR and

NPDLW obtained lower scores than the SALR and SALW(Table 17). As these genotypes were not necessarilyrepresentative of the South African population the conclusionto be drawn from these results is that sensory traits areinfluenced by types in a population. The SALR and SALWwere fatter than the NPDLR and NPDLW which could possiblybe associated with certain quality traits of loin chops. Durocsare becoming more popular in the United Kingdom as theyhave more marbling at the same fat thickness than otherbreeds, resulting in meat that was considered to be more juicy(Wood, Jones, Francombe & Whelehan, 1986). Bonneau(1982) also points out that higher fat androstenone levels wererecorded in Large White or Yorkshire boars in work done byRhodes & Patterson (1971). It is therefore important toevaluate the meat quality of genotypes to determine whichsuperior quality parameters of a certain genotype could beused to enhance the pork quality.



87

PARAMETER LIVE MASS GROUP53 kg 68 kg 87 kg 110 kg

pH1 electrode 6,24 6,21 6,18 6,19pH24 electrode 5,57 5,61 5,55 5,56FOP 139a 145b 147b 154c

EEL: Average 30 30 31 32Fat softness meter 473a 452a 505b 540c

Fat thickness (P2) 1,38a 1,70b 2,20c 2,85d

Fat thickness (T 3/4) 1,20a 1,44b 1,77c 2,18d

Iodine value 73a 70a 67b 64c

Refraction index 1,460a 1,460ab 1,459b 1,459babc Means in the same row with different superscripts differ significantly(P<0,05)

TABLE 14: The influence of live mass on meat and fatquality characteristics.

PARAMETER pH24 electrode FOP EEL T 2/3 - 45pH1 electrode 0,1845

**-0,3808

**-0,2275

**-0,3547

**pH24electrode

-0,1188NS

-0,0330NS

-0,0505NS

FOP 0,2858**

0,2422**

EEL 0,1743**

** P<0,05

TABLE 15: Correlation coefficients between meat qualitymeasurements.

PARAMETER IODINEVALUE

REFRACTIONINDEX

P2 T 3/4 - 60

Fat softnessmeter

-0,3250**

-0,2593**

0,4188**

0,3987**

Iodine value 0,6902**

-0,4410**

-0,4060**

Refraction in-dex

-0,3292**

-0,2415**

P2 0,9052**

** P<0,05

TABLE 16: Correlation coefficients between fat qualitymeasurements.


Sex condition significantly (P<0,05) influenced the odour,texture and fla-3-one, which itself may cause a detectableodour on some occasions in the fat when it is heated(Patterson, 1969). However, although �androstenone� is moreprevalent in discarded breeding boars, its level in boars raisedto pork or bacon weights is generally very low (Mottram, Wood& Patterson, 1982). The majority of consumers in England,Ireland and Sweden found no objectionable odours in pork andbacon from entire males (Walstra, 1974; Lesser, Baron &Robb, 1977; Cowan & Joseph, 1981; Malmfors & Lundström,1983). French results, that some consumers reacted to freshboar meat even with androstenone levels below 0,5 µg/g fat(Desmouling, Bonneau, Frouin & Bidard, 1982), imply that thepresence of other substances, such as skatole also intensifiedthe unpleasantness of boar odour (Lundström, Hansson,Fjelknermodig & Persson, 1980). It therefore seems that thecontroversy regarding boar �odour� will continue, until amethod is developed to determine boar �odour� on a movingslaughterline. Until such time the production of boars whichcould have a negative effect on the consumption of pork andbacon, should not be recommended in South Africa.


Results in Table 19 indicate that at 87 kg live mass sensorytraits of bacons were the most acceptable. This live mass is atthe moment the target mass for bacon production. Live masssignificantly (P<0,05) influenced juiciness and residue. Porkloins of the 87 kg mass group were less acceptable than thoseof the 53, 68 and 110 kg mass groups. It is therefore clear thatthe differences in meat quality of loins of the different livemass groups do not necessarily favour that of �porkers�.

CURRENT SITUATION IN SOUTH AFRICA

Presently 76 % of all pigs in South Africa are slaughtered inthe non-controlled area abattoirs. These abattoirs are mainlylarge processing plants and the bulk of the prominentcommercial and stud breeders deliver their pigs at theseabattoirs. Because the grading system that is applied in thecontrolled areas, is not mandatory in the non-controlled areas,

most of these abattoirs have adopted their own version of thecurrent grading system for pig carcasses and this has led tomuch confusion in the industry. One of the most importantproblems with the current pig carcass grading system is thelarge variation in fat thickness within each grade. The gradeSuper has a variation from 5-20 mm. From a consumer's point



88

PARAMETER GENOTYPESALR SALW NPDLR NPDLW

BACONSOdour 4,47a 4,35a 4,05b 4,48a

Texture 4,86a 4,45b 4,55b 4,74a

Juiciness 4,61a 4,32b 4,64b 4,63b

Flavour 4,46ab 4,22a 4,23a 4,53b

General Acceptability 4,33 4,25 4,27 4,44LOINS

Odour Fat 3,23ab 3,40b 3,06a 3,09a

Odour Meat 3,38ab 3,53b 3,13c 3,26ac

Initial Juiciness 3,75a 3,77a 3,49b 3,43b

Sustained Juiciness 3,30a 3,35a 2,97b 2,79b

Tenderness 3,49a 3,31ab 3,14bc 3,00c

Flavour 3,55a 3,59a 2,88b 2,89b

Residue 3,43a 3,33a 3,31a 3,13b

General Acceptability 3,44a 3,48a 2,76b 2,78babc Means in the same row with different superscripts differ significantly(P<0,05)

TABLE 17: The influence of genotype on the sensoryevaluation of bacons and lions.

PARAMETER SEX CONDITIONBOAR BARROW GILT

BACONSOdour 4,16

a4,38

ab4,47

b

Texture 4,52a

4,68b

4,73b

Juiciness 4,51 4,59 4,56

Flavour 4,15a

4,37ab

4,55b

General Acceptability 4,26a 4,26a

4,43b

LOINSOdour Fat 2,76

a3,40

b3,38

b

Odour Meat 3,17a

3,38b

3,41b

Initial Juiciness 3,71 3,58 3,55

Sustained Juiciness 3,18 3,08 3,06

Tenderness 3,19 3,25 3,28

Flavour 3,06a

3,29b

3,33b

Residue 3,27 3,33 3,32

General Acceptability 2,93a

3,21b

3,19b

abc Means in the same row with different superscripts differ significantly(P<0,05)

TABLE 18: The influence of sex condition on the sensoryevaluation of bacons and loins.

of view this is unsatisfactory. The parameters used in thecurrent grading system, i.e. carcass mass and the P2-fatthickness, are not sufficiently accurate to estimate carcasslean yield, and to describe the meat yield of a particular gradereliably to the end consumer. This was confirmed by theresults of this study. In the current system these parametersare used to predict % lean, which is however not calculatedand recorded for trading and marketing purposes. The

advantage of the HGP is that it can perform this function onthe slaughter line directly while the Intrascope does not havean electronic data logging and statistical calculation facility.Manual recording of fat measurements for later calculation andapplication is inefficient and may lead to recording errors.

THE PROPOSED NEW PIG CARCASS

CLASSIFICATION AND GRADING SYSTEM IN

THE RSA

Quantitative approach

Percentage lean should be the basis of a new classificationsystem. It should be the aim of any pig producer to producethe optimum amount of lean with the preferred amount of fat,which is the kind of product complying with the wide range ofconsumers' needs.

The following formulae should be used for the prediction of %lean:HGP% Lean = 72, 5114 - 0,4618V + 0,0547SV = Fat thickness (mm) and S = Muscle depth (mm) at theT2/3-45 positionINTRASCOPE% Lean = 74,4367 - 0,4023VV = Fat thickness (mm) at the T2/3-45 positionWithin each mass range the following % lean and fat thicknessclasses can be obtained:

An incentive could then be paid for carcass which produce ahigher % lean than the average of 67 % while those carcasswhich tend to be overfat could be penalized. The system ofpayment should encourage producers to breed and producethe required pigs which will give them the best income. It willalso enable private abattoirs to devise their own paymentsystems without altering the principles of classification. It isalso possible to use the Intrascope in such a system bytransforming the Intrascope % lean to a HGP % lean with acorrection factor. This would be suitable for smaller abattoirsslaughtering less than 50 pigs a day.

Qualitative approach

Results regarding the meat quality of the pigs cannot beignored in a grading system. Aspects of major concern are theincidence of PSE meat, boar odour and fat qualitycharacteristics. The results of this study have showed clearlythat the meat quality of boars was inferior to those of barrowsand gilts. Fat quality is a major problem in the pig industryespecially regarding soft fat (unsaturated fatty acids). Althoughdiet of the pig plays an important role in fat quality, it was also



89

PARAMETER LIVE MASS GROUP (kg)53 68 87 110

BACONSOdour 4,41 4,36 4,30 4,28Texture 4,44a 4,75b 4,76b 4,66b

Juiciness 4,15a 4,65b 4,74b 4,69b

Flavour 4,20a 4,48ab 4,49b 4,28ab

General Acceptability 4,26a 4,47b 4,46b 4,08a

LOINSOdour Fat 3,19 3,11 3,24 3,26Odour Meat 3,41 3,31 3,35 3,21Initial Juiciness 3,69a 3,73a 3,46b 3,56ab

Sustained Juiciness 3,26a 3,22a 2,92b 2,99b

Tenderness 3,38a 3,23ab 3,11b 3,24ab

Flavour 3,28 3,20 3,23 3,20Residue 3,44a 3,28ab 3,19b 3,30ab

General Acceptability 3,20 3,11 3,12 3,04abc Means in the same row with different superscripts differ significantly(P<0,05)

TABLE 19: The influence of live mass on the sensoryevaluation of bacons and loins.

% LEAN CLASSES P2 (mm)INTRASCOPE

T 2/3 - 45 (mm)HGP

<60% >32 >3060 - 61 % 32 - 30 30 - 2861 - 62 % <30 - 28 <28 - 2662 - 63 % <28 - 26 <26 - 2463 - 64% <26 - 24 <24 - 2264 - 65 % <24 - 22 <22 - 2065 - 66 % <22 - 20 <20 - 1866 - 67 % <20 - 18 <18 - 1667 - 68 % <18 - 16 <16 - 1468 - 69 % <16 - 14 <14 - 1269 - 70 % <14 - 12 <12 - 10

>70 % <12 <10

established that the fat quality of boars was less acceptablethan that of barrows and gilts. Clear indicators are also foundin literature that the leanness of pigs is a direct cause in thisregard. Therefore to urge producers to produce leaner pigsmay result in meat quality problems which will have adetrimental effect on the pig industry. A clear balance betweenthe quantitative and qualitative traits of the product isnecessary, as it has been established that the consumer inSouth Africa does not want more than 6 mm fat on a porkchop. From a producer and scientific point of view it isimpractical to produce pigs with such a thin layer of fat withoutrunning into other problems such as low reproduction rate,PSE meat and poor fat quality. This situation has alreadyoccurred in Europe. The only way by which the consumer canbe supplied with this lean chop is to derind and to trim the fatof the pork cut. The problem with trimming is that carcassloose their classification identity which may be undesirable forthe pig meat industry of this country.

CONCLUSION

In the present grading system boar carcasses are identifiedand graded accordingley due to the possibility of inferior meatquality. In the proposed classification system it is seen thatcarcasses which produce the highest amount of lean, will getthe highest incentive. On the other hand sub-optimal meat andfat quality may pose a problem with these carcasses, forexample PSE meat and soft fat. Therefore a close balancehas to be achieved between the quantitative and qualitativeapproach. An approach that could be followed in the industryis to penalise carcasses showing symptoms of PSE meat, boarcarcasses and carcasses that are too lean (<5 mm). It isimportant that this information should supplied to the tradethrough a well developed data base system where thefollowing information is of importance, i.e. % lean, fatthickness, muscle thickness, sex condition, PSE or not, as wellas even firmness of fat. The HGP has been found to reliablymeasure quantitatively and give qualitative indications. The pigproducer is unable to produce the kind of product in terms ofleanness that the consumer demands and at the same time aproduct of optimal quality. The dispensation to derind and trimthe fat of grades Super, 1 and 2 in the current grading systemwas therefore granted to the trade. When introducing the newsystem this situation should not change. The practise oftrimming pig carcasses is accepted and applied internationally.In conclusion it seems that there should be a classificationsystem for the producer and trade. It will be the retailer'sresponsibility to supply the consumer the amount of fat that hewants through defattening the product. Brand marking couldtherefore play an important role at the consumer level.

ACKNOWLEDGEMENTS

Various researchers and technicians have participated in thisproject and its success is due to their efforts. Therefore wewould like to thank them for their contribution. Mrs Walda Bokfor preparing the visual aids and Mrs Annette Honeyborne forthe typing of the manuscript. The following organizationscontributed generously in the financing of the project for whichwe are most grateful:1. Kanhym (Pty) Ltd2. Meat Board3. Transvaal - PDA

REFERENCES

ALLEN, P., 1986. Pig Carcass Grading - A new scheme andAutomated equipment. Farm & Food Res. 17, 4, 119.

ANONYMOUS, 1986. Developments in pig carcassclassification methods. Meat and Livestock Commission

BRUWER, G.G., 1986. A survey of pig carcass characteristicsin South Africa. Proc. 4th Meat Symp. ADSRI, Irene.

CHRISTIANS, C.J., 1981. Crossbreeding programs forcommercial pork production. Pork Industry Handbook,Extension folder 361, 1-6.

COWAN, C.A. & JOSEPH, R.L., 1981. Production and qualityof boar and castrate bacon. II. Consumer and panelresponse to bacon and fat samples. Ir. J. Food Sci.Technol. 5, 105

DESMOULIN, B., BONNEAU, M., FROUIN, A & BIDARD, J.P.,1982. Consumer testing of pork and processed meat fromboars: The influence of fat androstenone levels. Livest.Prod. Sci. 9, 707.

ELLIS, M., SMITH, W.C., CLARK, J.B.K. & INNIS, N., 1983. Acomparison of boars, gilts and castrates for baconmanufacture. 1. On farm performance, carcass and meatquality characteristics and weight loss in the preparation ofsides for curing. Anim. Prod. 37, 1.

KALLWEIT, E. & AVERDUNK, G., 1984. Perspectives forinstrumental techniques. In: Carcass evaluation in beefand pork - Opportunities and Constraints. SatelliteSymposium EAAP. The Hague, Netherlands.

KEMPSTER, A.J., 1986. The role of carcass grading and itsfuture. Scottish colleagues/MLC Conference �Pigmeat:improving appeal and production efficiencey�. Perth,Australia.

KEMPSTER, A.J. & EVANS, D.G., 1979. A comparison ofdifferent predictors of the lean content of pig carcasses. 1.



90

Predictors for use in commercial classification and grading.Anim. Prod. 28, 87.

KEMPSTER, A.J. & EVANS, O.G., 1981. The value of shapeas a predictor of carcass composition in pigs from differentbreeding companies. Anim. Prod. 33, 313.

KEMPSTER, A.J., CUTHBERTSON, A. & HARRINGTON, G.,1982. Carcass evaluation in livestock breeding, productionand marketing. Granada, London.

LESSER, D., BARON, P.J. & ROBB, J.D., 1977. Boar bacon: aconsumer survey. J. Sci. Fd. Agric. 28, 1120.

LUNDSTRÖM, K., HANSSON, K.E., FJELKNER-MODIG, S &PERSSON, J., 1980. Skatole - another contributor to boartaint. Proc. 26th Eur. Meat Res. Work. 1, 300.

MALMFORS, B. & LUNDSTRÖM, K., 1983. Consumerreactions to boar meat - a review. Livest. Prod. Sci. 8, 573.

MCGLOUGHLIN, P., LYNCH, P.B., HANRAHAN, T.J. & ALLEN,P., 1986. Evaluating the Duroc breed. Farm & Food Res.17, 4, 122

MONIN, G & P SELLIER, 1985. Pork of low technologicalquality with a normal rate of muscle pH fall in theimmediate post-mortem period: a case of the Hampshirebreed. Meat Sci. 13, 49-63.

MOTTRAM, D.S., WOOD, J.D. & PATTERSON, R.L.S., 1982.Comparison of boars and castrates for bacon production.3. Composition and eating quality of bacon. Anim. Prod.35, 75.

OMTVEDT, I.T., 1974. Maximizing genetic improvementthrough selection and crossbreeding. Proc. Working Symp.Breed Evaluation and Crossing Exp.., Zeist 1974, 2-11.

PATTERSON, R.L.S., 1968. 5-androst-16-ene-3-onecompound responsible for taint in boar fat. J. Sci. FoodAgric. 19, 31.

PEDERSEN, O.K., 1984. Pig carcass classification andgrading - relationship between quantitative and qualitativeaspects. In: Carcass evaluation in Beef and Pork-Opportunities and Constraints. Satellite Symposium EAAP.The Hague, Netherlands.

RHODES, D.N. & PATTERSON, R.L.S., 1971. Effect of partialcastration on growth and the incidence of boar taint in thepig. J. Sci. Fd. Agric. 22, 320.

SOMERS, C., TARRANT, P.V. & SHERRINGTON, J., 1985.Evaluation of some objective methods for measuring porkquality, Meat Sci. 15, 63.

WALSTRA, P., 1974. Fattening of young boars: quantificationof negative and positive aspects. Livest. Prod. Sci. 1, 187.

WALSTRA, P., 1989. Automated grading probes for pigscurrently in use in Europe, their accuracy, costs and use ofuse. New techniques in pig carcass evaluation. Proc.EAAP Symp. Helsinki, Finland, 1 July 1988. EAAPPublication No. 41.

WINSTANLEY, M., 1986. Maintain fat quality in lean pigs. PigsMarch 1986, 22-25.

WOOD, J.D. & RILEY, J.E., 1982. Comparison of boars andcastrates for bacon production. 1. Growth data andcarcass and joint composition. Anim. Prod. 35, 55.

WOOD, J.D., JONES, R.C.D., FRANCOMBE, M.A. &WHELEHAN, O.P., 1986. The effects of fat thickness andsex on pig meat quality with special reference to theproblems associated with overleanness. 2. Laboratory andtrained taste panel results. Anim. Prod. 43, 535-544.



91



92

N O T E S

ELECTRICAL STIMULATION AND MEAT QUALITY

P.H. HEINZE


INTRODUCTION

During recent years the improvement of meat quality hasgained importance due to consumer demand. This is a resultof increased buying power, improved education andinformation regarding nutritional value, the awareness of healthrisks associated with foods and food quality, more stringentquality criteria as a result of international trade, and thedevelopment of instruments used in analytical techniques (Ingr,1989). However, the definition of meat quality is extremelyproblematic as the perception of quality is influenced byfactors such as culture, education, social grouping etc. For thisreason, mainly the influence of electrical stimulation will bediscussed as they influence meat quality factors such astenderness and cooking loss, which may be the moreimportant quality characteristics. Taste panel members, ingiving their reasoning for ranking samples, indicatedtenderness to be most important (76 %), followed by flavour(14 %) and juiciness (10 %) (Cliplef & Strain, 1976).Furthermore, results obtained in research done at ADSRI willbe discussed regarding electrical stimulation of beef andrelated meat quality.

Before dealing with the question of electrical stimulation, it isnecessary to discuss the main reason which lead to the

development and implementation of electrical stimulation inSouth Africa, namely the rate of carcass chilling.

CARCASS CHILLING

Efficient chilling of carcasses after slaughter has beenaccepted as an essential part of the normal slaughterprocedure, having a direct influence on both the preservationand quality of meat.

Preservation of meat

The obvious reasons for chilling are the extension of shelf life,and to ensure �safe� and wholesome meat. As a result of thecomplex chemical composition of meat, which include variouscarbohydrates and proteins, it is an excellent medium forbacterial growth (Honikel & Hamm, 1983). These micro-organisms might be of pathogenic or spoilage importance.Chilling and freezing of meat inhibit the metabolism and growthof the micro-organisms to varying degrees as a result of theirdifferent temperature tolerances (Wirth, 1979).

Chilling also plays another important role in improving shelflife. Many proteolytic enzymes occur naturally in meat, and if



93

PAUL HEINZE is the Assistant Director of the Meat Production Physiology section within MeatScience, and is as such responsible for the coordination of activities in the section. Hisresearch activities focus on the use of electrical stimulation of beef and sheep carcasses. Heis also involved in the research on the Porcine Stress Syndrome, and has recently submitted aPhD thesis on the subject at the University of the Witwatersrand. He graduated from the RandAfrikaans University, obtaining a BSc in 1976 majoring in Chemistry and Biochemistry, and aBSc (Hons) in 1977, majoring in Biochemistry. He subsequently graduated in 1987 from theUniversity of Pretoria, obtaining a MBA. He is currently registered as a member of the SouthAfrican Council for Natural Scientists, the South African Society for Animal Production, and theSouth African Medical and Dental Council (medical technology).

left unabated, promotes spoilage and the deterioration of meatquality. These enzymes usually have a maximal activity rate athigher temperatures, and are inhibited by low temperatures.Also, other chemical reactions resulting in a loss of meatquality are influenced negatively by low temperatures, such asthe oxidation of fats (Heinz, 1977).

It is thus important to chill carcasses immediately afterslaughter to prevent high loads of micro-organisms developingon meat surfaces, to limit the metabolism rates and growth ofthese micro-organisms, to slow down proteolytic enzymesactivities, and to retard chemical reactions.

The chilling of carcasses in the Republic of South Africa isregulated by the meat hygiene regulations to ensure publicsafety and promoting a higher product quality. A deep bonetemperature of 10 °C must be reached after slaughter beforethe carcass may be released from an abattoir. To ensure thatsuch a temperature is reached, all chillers at abattoirs, in atleast the controlled areas, operate at a temperature of 0 °C.

Meat quality and chilling

Although chilling is of utmost importance in promoting shelf lifeand safety, the influence that this process may have on meatquality characteristics should be examined. Literature seems toindicate quite clearly that rapid chilling results in thetoughening of meat (Locker & Hagyard, 1963; Honikel &Hamm, 1978; Honikel & Hamm, 1983).

An experiment was therefore designed at the ADSRI toexamine the influence of beef carcass chilling rates on cookingloss and tenderness of the muscles M. semitendinosus (ST),

M. longissimus lumborum (LL) and M. longissimus thoracis(LT). Some of the factors taken into account during theexperiment were cold room temperature (0, 3, 5, 7 and 9 °C),carcass mass (111, 152, 202 and 252 kg) and mode ofsuspension of the carcass (pelvis vs Achilles tendon).

Influence of carcass mass on meat quality

The influence of carcass mass on cooking loss is given inTable 1. The tendency in the ST is a general reduction(P≤0,01) in the cooking loss with an increase in carcass mass.In the LL and LT the decrease in cooking loss (P≤0,01) withan increase in carcass mass was found from 111 kg to 152 kg,after which it remained approximately the same for the othermass groups. Regarding tenderness (Table 1), carcass masshad no influence on the ST and LL (P>0,05). However, thetenderness of the LT increased (P≤0,01) with carcass massfrom 111 kg to 202 kg after which it decreased again.

It therefore seems that an increase in carcass mass wouldincrease tenderness up to a carcass mass of approximately202 kg, after which it would increase again. This increase incarcass mass is also beneficial in terms of a lower cookingloss.

Chilling temperature and meat quality

The influence of carcass chilling on cooking loss is given inTable 2. Chilling temperature had an influence (P≤0,01) on allthree the muscles (ST, LL and LT). An initial decrease wasfound with an increase in chilling temperature from 0 to 3 °C.Increasing the chilling temperature above 3 °C resulted in an



94

Variable Carcass mass

111 kg 152 kg 202 kg 252 kg

Cooking loss (%)

M. semitendinosus 28,7a 27,1a 27,5b 26,2c

M. longissimus lumborum 28,6a 26,7b 27,3c 26,9bc

M. longissimus thoracis 25,8a 24,6bc 25,1b 24,4c

Shear force N/19 mm dia.

M. semitendinosus 148a 132a 112a 140a

M. longissimus lumborum 173a 154a 132a 140a

M. longissimus thoracis 162a 141b 120c 132bc

abc Values with different superscripts in each row differ P≤0,05

TABLE 1: Influence of carcass mass during chilling on the cooking loss and shear force of the muscles M. semitendinosus,M. longissimus lumborum and M. longissimus thoracis

increase in the cooking loss, therefore a clear negativeinfluence as far as cooking loss is concerned.

Chilling temperatures apparently had no influence (P>0,05) onthe tenderness of the ST (Table 2), which is similar to thefindings of Joseph & Connolly (1977). However, chillingtemperature influenced the tenderness of both the LL and LTsignificantly (P≤0,01) (Table 2). With an increase in the chillingtemperature an increase in tenderness resulted, also found byCliplef & Strain (1976). Clearly, the decrease of chillingtemperature had a negative influence on meat tenderness.This phenomenon is called cold shortening (Locker & Hagyard,1963), and is associated with a toughening effect on meat.

Cold shortening

To explain cold shortening, it is important to firstly discuss thecontraction and relaxation processes in muscle briefly. Thecontraction of muscle is usually the consequence of a neuralstimulus, resulting in the release of asetylcholine in the motor-end plates, the interface between the nerve end and themuscle. The asetylcholine promotes the release of calciumions from the sarcoplasmic reticulum of the muscle cell into thesarcoplasm. The calcium concentration increases in thesarcoplasm, and initiates contraction of the muscle by bindingthe protein troponin of the actin filament, thereby releasing theinhibiting effect of troponin and tropomyosin. Cross bindingsbetween the actin and myosin filament are established,resulting in the contraction of the muscle. This action requiresenergy in the form of ATP (Hamm, 1979).

Relaxation of the muscle can be visualised as the opposite tocontraction. The calcium ions are actively �pumped� out of thesarcoplasm into the sarcoplasmic reticulum via the so-calledcalcium pumps which are imbedded into the membrane of thesarcoplasmic reticulum. These calcium pumps require ATP asenergy source. As the calcium ion concentration in thesarcoplasm is lowered, troponin and tropomyosin resume theirrole in inhibiting contraction. The cross bridges are released,and the muscle relaxes (Hamm, 1979).

The ATP necessary for these processes are derived fromaerobic and anaerobic glycolysis and glycogenolysis. However,anaerobic glycolysis, which requires no oxygen, is only 112 asefficient as aerobic glycolysis in ATP production(Honikel &Hamm, 1978). Both these processes are active in the liveanimal. However, when the animal is slaughtered, the jugularvein is severed and hence the oxygen supply is terminated.The animal tissues still attempt to maintain homeostasis, forinstance to prevent muscle contraction, for which energy isrequired. ATP is used, and the diminishing levels of ATPstimulates ATP production, but only by anaerobic glycolysis(Bendall, 1973). This leads to the lowering of the pH levels inthe muscles due to lactate formation. However, the glycogenand glucose reserves in the cells are limited, and cannot bemaintained. Not enough ATP exists in the muscle to maintainthe function of the calcium pumps, and the calciumconcentration slowly increases in the sarcoplasm, resulting inirreversible muscle contraction, and rigor mortis. This is arelatively slow process, and not necessarily detrimental totenderness (Honikel & Hamm, 1978).



95

Variable Chilling temperature

0 °C 3 °C 5 °C 7 °C 9 °C

Cooking loss (%)

M. semitendinosus 26,9a 26,0b 27,5c 28,0c 28,6d

M. longissimus lumborum 28,6a 25,4b 26,9c 27,4c 28,6a

M. longissimus thoracis 25,5a 23,0b 24,5c 25,0ac 26,8d

Sheare force N/19 mm dia.

M. semitendinosus 144a 132a 132a 127a 125a

M. longissimus lumborum 205a 164ab 150bc 125bcd 106d

M. longissimus thoracis 200a 152b 130c 110d 100d

abcd Values with different superscripts in each row differ P≤0,05

TABLE 2: Influence of chilling temperature during chilling on the cooking loss and shear force of the musclesM. semitendinosus, M. longissimus lumborum and M. longissimus thoracis

However, when muscles are chilled directly after slaughter andbefore rigor mortis sets in, the energy reserves are still high. Ifthe muscle is chilled to a temperature of less than 10 to 12 °C,the calcium pumps are slowed down and are less effective inpumping the calcium out of the sarcoplasm. The end result isan accumulation of calcium in the sarcoplasm, and contractionof the muscle. ATP is used during this contraction, and as theATP concentration drops (to below 20 % of the in vivoconcentration (Hamm, 1977)) rigor mortis sets in during a timethat the muscle is contracted and the meat is toughened.Cornforth, Pearson & Merkel (1980) also imply themitochondria in the cold shortening process because of coldshortening being a phenomenon of red muscles, and not whitemuscles. They reason that as a result of the anoxic situationpost mortem, mitochondria which are more abundant in redmuscle, and also accumulate calcium, lose their ability toaccumulate calcium. The calcium concentration in thesarcoplasm increases even before the muscle is chilled, butdoes not lead to muscle contraction. The sarcoplasmicreticulum is still able to accumulate the addi-1 °C shouldprevent cold shortening. Clearly this is impractical should adeep bone temperature of 10 °C be sought within probably 18hours as is required for abattoirs in the controlled areas. Also,bacteriological implications could have a negative effect onboth safety and shelf life.

Mode of carcass suspension

Another possibility would be the physical prevention of coldshortening by �stretching� the muscle after slaughter until rigormortis sets in. This might be possible when applying the�tenderstretch� (Joseph & Connolly, 1977) mode of suspensionin which carcasses are suspended from the pelvis instead ofthe Achilles tendon. This was examined in the experimentpreviously discussed which was conducted by the researchersof the Meat Science Centre.

Regarding cooking loss, mode of suspension had no influence(P>0,05) on the muscles ST and LT. However, the cookingloss of the LL was reduced (P≤0,01) using the pelvissuspension method (Table 3). Although mode of suspensionhad no influence on the tenderness of the ST (P>0,05), whichwas similar to the results obtained by Joseph & Connolly(1977), both the LL and LT were more tender (P≤0,01) whenthe pelvis method of suspension was used (Table 3). This wassimilar to the findings of Joseph & Connolly (1977) for the LT.However, Dreyer, Van Rensburg, Naudé, Gouws & Stiemie(1979) found the ST to be more tender using the pelvismethod of carcass suspension. Nevertheless, the pelvismethod of suspension is not conducive to normalslaughterhouse practices. Only certain muscles are affectedpositively by this method i.e. LL and LT; not all muscles arestretched i.e. ST. Therefore other means of preventing orminimising the influence of cold shortening should be sought.

If the initial energy reserve levels in the muscles could belowered before or during the slaughter process, less energywould be available for severe contraction when the carcass ischilled.

REDUCING ENERGY RESERVES

Reducing energy reserves could be brought about in the liveanimal or in the carcass before chilling commences.

Reducing energy reserves in the live animal

prior to slaughter

Reducing the energy reserves in the live animal beforeslaughter could be brought about by starvation, or by stressingthe animal ante mortem over a period of time. This wouldreduce glycogen reserves, leading to rigor mortis setting inquicker, even before chilling with little possibility of coldshortening.

However, various ethical and quality factors would prevent theuse of these methods which are inhumane and consequentlyunacceptable. Furthermore, carcasses of exhausted animalsproduce dark, firm and dry (DFD) meat, with a high ultimatepH (>6,00 24 hours post mortem) which have negative meatquality characteristics such as a short shelf life (Newton & Gill,1981).

Reducing energy reserves immediately post

mortem

It has already been mentioned that muscle contraction per seuses energy. Swammerdam in 1663 demonstrated thatsending an electrical current through a nerve in a muscleresults in muscle contraction (Bendall, 1980). Galvannidemonstrated in the 1780's that passing an electric currentthrough muscle also results in contraction (Bendall, 1980).Therefore, if carcasses could be electrically stimulated, themuscles will contract and this should lead to a reduction ofenergy reserves, and hence more tender meat. An experimentto this effect was conducted at the ADSRI to evaluateelectrical stimulation and meat tenderness.

EXPERIMENTS AND SURVEYS CONDUCTED

ON ELECTRICAL STIMULATION BY THE

MEAT SCIENCE CENTRE

An experiment on electrical stimulation was conducted at theADSRI before any commercial electrical stimulators wereinstalled at abattoirs in South Africa. However, after theinstallation of commercial electrical stimulators, surveys wereconducted under experimental conditions to establish theireffectiveness.



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Experiment on electrical stimulation at

ADSRI

Beef carcasses were dehided, eviscerated and split. Left sideswere electrically stimulated at 500 V and 10 Hz for 120seconds, alternating the polarity every 20 seconds. The rightsides were not electrically stimulated and were used ascontrols. All sides were chilled at 0 °C. Electrical stimulationcould only be applied about 45 minutes post mortem as aresult of the experimental design chosen. The influence of theelectrical stimulation was evaluated according to the followingmeat quality characteristics: pH values, cooking loss, waterholding capacity, sarcomere lengths, tenderness according toa taste panel and shear force measurements 3 days postmortem.

pH values

The pH values were determined in the LT and the results areshown in Fig. 1. As a result of the late stimulation procedurefollowed, the pH values 45 minutes post mortem did not differ(P>0,05) between the stimulated and non-stimulated group.However, the pH values of the stimulated group were lower(P≤0,05) at 2, 3, 4, 5, 6, 7 and 24 hours post mortem,indicating that electrical stimulation was effective in loweringthe pH values of the muscle, and therefore the energyreserves in the muscle. Nevertheless, according to thetheoretical criterion for an effective electrical stimulation of apH value of 6,00 or lower within 60 minutes post stimulation(Anon., 1981), the method employed here was not effective.

Evidence indicates that the activation of contraction byelectrical stimulation is through the nervous system in thecarcass (Bendall, 1980). Therefore, the longer the time period

between slaughter and electrical stimulation, the lower theefficiency of the nervous system to activate musclecontraction. This might be the reason for the pH value >6,0060 minutes post stimulation in the present study. The nervoussystem simply �dies�. Therefore the voltage and the duration ofelectrical stimulation should be increased the longer the timeperiod between stunning and stimulation (Fig. 2) (Anon.,1981).

Cooking loss

Cooking loss was also not influenced by electrical stimulation(P>0,05), whether the meat samples (200 g) were cooked at60 or 80 °C for 60 minutes (Table 4). No influence (P>0,05) byelectrical stimulation was found on the water holding capacity(Table 4).

Tenderness and sarcomere length

However, although the electrical stimulation was not effective(Fig. 1) as deemed by the pH criterion 60 minutes poststimulation (Anon., 1981), it still was effective in reducing(P≤0,01) the shear force of meat samples cooked at either 60or 80 °C by between 71 and 86 % (Table 4). These resultswere also obtained from a trained taste panel which deemedthe electrically stimulated meat as being 50 % more tender(P≤0,01), a result substantiated by lower (P≤0,01) shear forcemeasurements on the meat prepared for the taste panel(Table 4). The reason for the more tender meat could befound in the phenomenon of the sarcomere lengths in themuscle of the electrically stimulated sides being greater(P≤0,01) (Table 4), indicating that rigor mortis had set in at astage when the muscles were at a more relaxed state than themuscles of the control group. The lower pH values of theelectrically stimulated group, having the longer sarcomerelengths, indicate the reduction of energy reserves in themuscle and hence less cold shortening. Effective electricalstimulation may reduce ATP reserves by 50 % within 60minutes (Bendall, 1980).

After a few electrical stimulators were installed at commercialabattoirs in South Africa, the researchers of the Meat ScienceCentre were requested to evaluate the effectiveness of thesestimulators under commercial circumstances.

High voltage electrical stimulation 40

minutes post mortem

Carcasses were selected according to mass (160 and 220 kg)and age (no permanent incisors (p.i.) and 2-4 p.i.). Thecarcasses were electrically stimulated at 396 or 500 V 40minutes post mortem for 120 seconds. A control group whichwas not electrically stimulated was also selected. Electrical



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Variable Muscle

ST LL LT

Cooking loss (%)

Achiless tendon 27,5a 27,7a 25,1a

Pelvis 27,3a 27,1b 24,8a

Shear force N/19 mm dia

Achiless tendon 134a 180a 168a

Pelvis 130a 120b 109b

ab Values with different superscripts in each column differ P≤0,05

TABLE 3: Influence of mode of suspension on cookingloss and shear force of beef carcasses duringchilling

stimulation took place after the hide had been removed, butbefore evisceration. pH values were determined 2 and 36hours post mortem in the LT in the region of the 12th thoracicvertebrae. The pH 2 hours post mortem gives an indication ofthe effectiveness of stimulation, whereas the pH 36 hours postmortem was determined to identify DFD carcasses whichcannot be used to evaluate efficiency (exhausted animals withDFD characteristics have an ultimate pH value >6,00). Two

and ten days post mortem samples of the LT of the wingribwere cooked at 70 °C for 60 minutes, and the cooking lossdetermined as well as shear force values which indicatetenderness.

Treatment resulted in significant differences (P≤0,01) in pHvalues 2 hours post mortem. Electrical stimulation resulted in apH value 2 hours post mortem of less than 6,00 (396 V=5,75and 500 V=5,60) whereas the control group still had anaverage pH value of 6,66 (Table 5). According to the criterionset of a pH value 60 minutes after stimulation of 6,00 or less(Anon., 1981), the stimulation at both 396 and 500 V wereclearly most effective.

Although age and carcass mass had no influence (P>0,05)(Table 5) on the tenderness of the meat two days postmortem, treatment had (P≤0,01) (Table 5). The control groupwas the toughest (85 N/13 mm dia.), compared to the 68 and50 N/ 13 mm dia. of the 396 and 500 V groups. The pH value2 hours post mortem indicated a severe stimulation ofglycolysis in the electrically stimulated groups and therefore areduction of the energy reserves, resulting in more tendermeat. However, an increase (P≤0,01) in cooking loss wasfound in the stimulated groups (Table 5), increasing from the19,26 % in the control group to 22,29 and 21,45 % in the 396and 500 V electrically stimulated groups.

Meat from the same carcasses 10 days post mortem stillshowed a significant influence (P≤0,01) of treatment. Theelectrically stimulated groups still had the most tender meat(396 V = 38 N/13 mm dia.; 500 V = 32 N/13 mm dia.), whilethe control group still had a shear force value of 52 N/13 mmdia. (Table 5). Thus, even with an additional 8 day ageing



98

FIGURE 1: pH value decline of the M. longissimus thoracis of non-stimulated and electrically stimulated (500 V, 10 Hz,duration 120 seconds) beef sides

FIGURE 2: The relationship between time post mortem,electrical stimmulation voltage and duration(Anon., 1981)

period, the meat from electrically stimulated carcasses was stillmore tender. Therefore, electrical stimulation even acceleratesthe natural tenderisation of meat (Bendall, 1980). The meatfrom the control group also aged, but it is interesting to notethat only after 10 days the meat of the control group hadapproximately the same tenderness as the electricallystimulated meat after only 2 days, clearly an enormousadvantage. Furthermore, it has been found that the tougheningef-260, >260 kg). The carcasses stimulated at 500 V werestimulated within 11 minutes of stunning for 66 seconds, andthose stimulated at 30 V within 90 seconds after stunning for60 seconds (according to the distributor). However, stimulationby the low voltage was actually 40 seconds, which comprisedof a 2 second stimulation period followed by a 1 second periodof no stimulation during the total of 60 seconds. Again pHvalues were determined 2 hours post mortem in the LT in theregion of the 12th thoracic vertebrae to determine theeffectiveness of electrical stimulation, and at 24 hours postmortem to identify any DFD carcasses which would not besuitable for inclusion in the study.

Treatment had a significant (P≤0,01) effect on pH values 2hours post mortem (Table 6). The 500 V stimulated carcasseshad an average pH value of 5,83 compared to the 6,70 of thecontrol group. The 30 V stimulated carcasses only had anaverage pH value of 6,54, indicating clearly an ineffectivestimulation. Again, no significant influence (P>0,05) was found

in carcass mass (Table 6). Therefore, mass did not influencethe effectiveness of electrical stimulation in reducing energyreserves.

Low voltage electrical stimulation could be effective if certainprecautions were taken. These precautions are:

- to use an additional earth contact in the anal or rump re-gion as the shackle and upper leg has a high resistance,thus reducing the current flow (Powell, Harris & Shorthose,1986)

- to stimulate within 8 minutes after stunning- electrical stimulation duration of at least 90 seconds at45 V (Anon., 1981).

The low voltage electrical stimulators in Australia operate at45 V, which is the legal limit for electrical stimulators incommercial abat- and Z- lines (Savell, Dutson, Smith &Carpenter, 1978), therefore actively tenderising the meat. Wehave conducted an experiment to determine the influence ofelectrical stimulation on the toughness of meat undercircumstances which should not lead to cold shortening. Leftsides of beef carcasses were not elecrically stimulated andused as the control group, whereas the right sides wereelectrically stimulated at 500 V 45 minutes post mortem. Allcarcasses were kept at about 11 °C for 5 hours post mortem,and then chilled at temperatures of 7 °C. The shear forcevalues and sarcomere lengths of the LT 2 days post mortemof the control and experimental sides were similar (P>0,05)(Table 7). It was concluded that electrical stimulation, in theabsence of conditions condusive to cold shortening, did nottenderise the meat to such an extent that it could be detectedby shear force or sarcomere length measurements.

ELECTRICAL STIMULATION AND

CONNECTIVE TISSUE

According to the discussion on cold shortening, electricalstimulation prevents cold shortening which is the result of rigormortis setting in while the muscle is in a contracted state.Hence, cold shortening is influenced by the contractileproteins. The question is how the connective tissue proteinsinfluence meat tenderness, and whether electrical stimulationhas a positive influence on this aspect.

With increasing age, collagen (the most important connectivetissue in muscle with regard to tenderness) undergoes certainchanges, changing the protein from a more soluble to a lesssoluble protein as a result of permanent physical bondsbetween the collagen filaments. This process has a negativeinfluence on tenderness. Therefore, the reduction in energyreserves as a result of electrical stimulation has no effect onthe toughness resulting from collagen. Accordingly, the older



99

Variable Control group Electrical stimula-tion (500 V)

Cooking loss (%)

Samples cooked at 60 °C 12,9a 12,3a

Samples cooked at 80 °C 35,4a 36,1a


Samples cooked at 60 °C 67a 39b

Samples cooked at 80 °C 123a 66b

Water holding capacity (%)Samples cooked at 70 °C 44,2a 44,4a

Sarcomere length 1,56a 1,72b

Taste panel score 2,2a 3,3b

TABLE 4: Influence of electrical stimulation (500 V) oncooking loss, shear force, sarcomere length,water holding capacity and taste paneltenderness score

the animal, the tougher the meat will be, whether electricallystimulated or not.

ADDITIONAL ADVANTAGES OF ELECTRICAL

STIMULATION

Electrical stimulation also accelerates the so-called �blooming�

of meat (Bendall, 1980). The muscles of the electricallystimulated carcasses therefore have a brighter red colour(Tang & Henrickson, 1980; Savell, McKeith, Murphey, Smith &Carpenter, 1982). This is a result of the rapid exhaustion of

the substrates and intermediates in the oxidative processes inthe muscles which consequently reduces the utilisation ofoxygen from the air. This allows the deeper penetration of thisoxygen into the meat, increasing the depth of the bright redlayer of oxy-myoglobin. This could not be reproduced in the LLusing low voltage electrical stimulation, although theM. semimembranosus was lighter in colour (Ledward,Dickinson, Powell & Shorthose, 1986).

Another most important advantage of electrical stimulation andthe accelerated onset of rigor mortis, is that it facilitates hotboning of carcasses (Cross, 1979). The process of hot boninghas the advantage of a reduction in time, space andrefrigeration capacity required to produce meat of high quality.The chilling rooms would not have to cater for whole beefsides, but only for vacuum packed joints requiring lessrefrigeration capacity (Taylor, Shaw & MacDougall, 1980).

CONCLUSION

Low chilling temperatures after slaughter result in the coldshortening of muscles in beef, which are consequentlytoughened. This phenomenon is also influenced in certainmuscles by carcass mass, with the tendency of a highertenderness with increasing carcass mass up to a mass ofabout 202 kg.

Various methods could be employed to prevent coldshortening:

- carcass suspension from the pelvis - however, this methodseems to be impractical, and not all the muscles benefitby the treatment.



100

Variable Electrical stimulation voltage

0 V 396 V 500 V

pH2 hours post mortem 6,66a 5,73b 5,60b


2 days post mortem 85a 68b 50c

10 days post mortem 52a 38b 32b

Cooking loss (%) 19,26a 22,29b 21,45ab

Variable Animal age

0 Permanentincisors

2-4 Permanantincisors

Shear force N/13 mm dia 77a 68a


160 kg 220 kg

Shear force N/13 mm dia 72a 72a

ab Values with different superscripts in each row differ P≤0,05

TABLE 5: Influence of electrical stimulation (high)voltage, age and carcass mass on shear forceand/or pH values two hours post mortem ofthe M. longissimus thoracis

Variable Control group 500 V

Shear force (N/13 mm dia.) 62a 51a

Sarcomere length µm 54a 57a

a Values with same superscripts in each row do not differ (P>0,05

TABLE 7: Influence of electrical stimulation (500 V) onshear force and sarcomere lengths 2 dayspost mortem if chilled under conditions notconducive to cold shortening

Variable Electrical stimulation voltage

0 V 30 V 500 V

pH value 2 hours postmortem

6,70a 6,54b 5,83c


<140 kg 141-180kg

181-220kg

221-260kg

>260 kg

pH value 2 hours postmortem

6,48a 6,39a 6,40a 6,41a 6,39a

abc Values with different superscripts in each row differ P≤0,05

TABLE 6: Evaluation of the influence of low and highvoltage electrical stimulation and carcassmass on the pH value two hours post mortemin the M. longissimus thoracis

- animal exhaustion before slaughter - this method is unethi-cal and also results in DFD meat, which is a negative de-viation from normal meat quality, and therefore not accept-able.

- delayed chilling preventing muscle temperature to drop tolower than 10 °C before rigor mortis sets in, safetly beingtaken as 10 hours post mortem - this method is also im-practicle due to meat hygiene regulations requiring car-casses to attain a deep bone temperature of less than10 °C before being transported. This is not possiblewhithin one day post mortem if carcasses are chilled at10 °C for the first 10 hours post mortem. Furthermore, itwould be uneconomical to chill carcasses for two days inorder to attain temperatures of lower than 10 °C in thedeep leg.

- electrical stimulation - this method is practical and effec-tive if used correctly. It decrease energy reserves in mus-cles early post mortem, leading to the onset of rigor mortiswhile the muscle temperature is still high, thus preventingcold shortening.

It has to be remembered that cold shortening is not an all-or-none phenomenon, but a process on a continuum which couldlead from a little cold shortening to extreme cold shortening,hence from a little toughening effect to super toughening ofmeat. It would seem that electrical stimulation does nottenderise meat, but only prevents the toughening effect of coldshortening, and only if applied correctly and effectively.

REFERENCES

ANON., 1981. Effective electrical stimulation of beef carcassesand sides. Meat Research News Letter 81/5, 1-7.

BENDALL, J.R., 1973. Post mortem changes in muscle. In:The structure and function of muscle, volume 3. Ed. H.O.Bourne. 2nd edition. New York Academ. Press, 227-274.

BENDALL, J.R., 1980. The electrical stimulation of carcassesof meat animals. In: Developments in meat science,volume 1. Ed. R. Lawrie. Applied Science Publishers,London. 37-59.

CLIPLEF, R.L., & STRAIN, J.H., 1976. Tenderness and relatedorganoleptic characteristics of beef carcass as affected bypostmortem chilling temperature. Can. J. Anim. Sci. 56,417-423.

CORNFORTH, D.P., PEARSON, A.M., & MERKEL, R.A.,1980. Relationship of mitochondria and sarcoplasmicreticulum to cold shortening. Meat Sci. 4, 103-121.

CROSS, H.R., 1979. Effects of electrical stimulation on meattissue and muscle properties - a review. J. Fd Sci. 44, 509-523.

DAVEY, C.L., KUTTEL, H., & GILBERT, K.V., 1967. Shorteningas a factor in meat ageing. J. Fd Technol. 2, 53-56.

DREYER, J.H., VAN RENSBURG, A.J.J., NAUDÉ, R.T.,GOUWS, P.J., & STIEMIE, SUZETTE, 1979. The effect ofchilling temperatures and mode of suspension of beefcarcasses on sarcomere length and meat tenderness. S.Afr. J. Anim. Sci. 9, 1-9.

HAMM, R., 1977. Post-mortem breakdown of ATP andglycogen in ground muscle: a review. Meat Sci. 1, 15-39

HAMM, R., 1979. Die Biochemie des Muskel-Calciums undihre Bedeutung für die Fleischqualität. Fleischwirtsch. 59,393-398.

HEINZ, G., 1977. Kühlen und Gefrieren von Fleisch aus neuerSicht. Fleischwirtsch. 57, 21-29.

HONIKEL, K.O., & HAMM, R., 1978. Einfluss des Kühlens aufdie Eigenschaften von frisch erschlachtem Rindfleisch.Fleischwirtsch. 58, 712-719.

HONIKEL, K.O., & HAMM, R., 1983. Kühlen, Gefrieren undAuftauen: Kolloidchemische Aspekte der Fleischqualität.Fleischwirtsch. 63, 1118-1127.

INGR, I., 1989. Meat quality: defining the term by modernstandards. Fleischwirtsch. 69, 1268-1270.

JOSEPH, R.L., & CONNOLLY, J., 1977. The effects ofsuspension method, chilling rates and post mortem ageingperiod on beef quality. J. Fd Technol 12, 231-247.

LEDWARD, D.A., DICKINSON, R.F., POWELL, V.H., &SHORTHOSE, W.R., 1986. The colour and colour stabilityof beef longissimus dorsi and semimembranosus musclesafter effective electrical stimulation. Meat Sci. 16, 245-265.

LOCKER, R.H., & HAGYARD, C.J., 1963. A cold shorteningeffect in beef muscles. J. Sci. Fd Agric. 14, 787-793.

NEWTON, K.G., & GILL, C.O., 1981. The microbiology ofDFD fresh meats: a review. Meat Sci. 5, 223-

POWELL, V.H., HARRIS, P.V., & SHORTHOSE, W.R., 1986.Beef tenderness - Australia 1985. Food Technology inAustralia 38, 230-233.

SAVELL, J.W., DUTSON, T.R., SMITH, G.C., & CARPENTER,Z.L., 1978. Structural changes in electrically stimulatedbeef muscle. J. Fd Sci. 43, 1606.



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SAVELL, J.W., MCKEITH, F.K., MURPHEY, C.E., SMITH, G.C.,& CARPENTER, Z.L., 1982. Singular and combined effectsof electrical stimulation, post-mortem ageing and bladetenderisation on the palatability attributes of beef fromyoung bulls. Meat Sci. 6, 97-109.

TANG, B.H., & HENRICKSON, R.L., 1980. Effect ofpostmortem electrical stimulation on bovine myoglobin andits derivatives. J. Fd Sci. 45, 1139-1145.

TAYLOR, A.A., SHAW, B.G., & MACDOUGALL, D.B., 1980.Hot deboning beef with and without electrical stimulation.Meat Sci. 5, 109-123.

WIRTH, F., 1979. Chilling, freezing, storage and thawing ofmeat: present state of our knowledge. Fleischwirtsch. 59,1857-1861.



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Documents

The Meat Animal and its Products Symposium documents... · CARCASS EVALUATION Beef, lamb and mutton carcass classification and grading in South Africa R.T. NAUDÉ, J.F.G. KLINGBIEL*