Livestock Production Science, 19 (1988) 197-209 197 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

II. 7. Compound Animal Feed and Feed Addit ives

A.P. NAMUR, J. MOREL and H. BICKEL

INTRODUCTION

The feeding of compound feed and the use of feed additives for animal pro- duction in Europe have grown considerably since the beginning of this century, especially over recent decades. These were developed by independent national and international companies as well as by agricultural cooperatives and by food-processing companies valorizing their own by-products. Today a strong compound-feed industry is marketing compound feed as complete rations, large supplements and premixes all over Europe. It has contributed significantly to the technical revolution and economical improvement of European livestock production. Animal feed is the largest single item of expense in the production of milk, meat and eggs, often accounting for up to 70% of total cost.

The high efficiency of present day animal production is achieved by the com- bined efforts of all concerned: (1) livestock farmers readily accept new tech- niques for improving the efficiency of their operations; (2) research has achieved valuable results in genetics, nutrit ion and management to produce quality products at the least possible cost; (3) governments foster the devel- opments in research, advise livestock farmers and issue the necessary regulations.

The feeding of compound feed, based on scientifically-calculated formulae, especially as complete rations (all-mash or pellets), to pigs and poultry can put the results of nutri t ion research and innovations to work in practice, very quickly and efficiently. Complete rations save labour on the farm, improve the efficiency of the feed and help to utilise new feed resources. The feed industry has a big impact, not only on the introduction of new feed resources into live- stock production, but generally on the whole trade with feedstuffs. This be- came even more important with the application of least-cost formulation by linear programming on computers.

The mixing of authorized feed additives into compound feeds to meet the requirement of the animal for specific minor nutrients, to improve perform- ance and to prevent disease, became a wide-spread practice. Moreover, com- pound feed can be used by veterinarians as medicated feed to prevent or cure diseases in large herds of animals, where individual treatments are very time and labour consuming.

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The cost of transportation, particularly of roughages, puts an economic limit on the use of complete rations on the farm. In many areas, livestock production depends essentially on home-grown feed, supplemented by feedstuffs not avail- able on the farm.

UTILIZATION OF COMPOUND FEED

General

Compound feeds can be classified according to their quantitive importance in the ration of the various animals. They are fed: (1) as complete diets (all- mash, pellets, crumbles ); (2) as basic diets to be supplemented by home-grown feed or by-products; (3) as quantitatively-important supplements to home- grown feed by-products; (4) as a vitamin/mineral pre-mix, representing quan- titatively a minor component of the ration.

The proportion of compound feed in the total ration, i.e. compound feed supplemented with a minor percentage of home-grown feed or, on the other extreme, home-grown feed with a minor part of supplements is highly variable. It depends on the feeding system for the particular livestock and on the re- sourses of feedstuffs available in the area under consideration. Therefore, we prefer to distinguish roughly between a complete diet and various types of sup- plements and pre-mixes.

Complete diet

A complete diet is the usual method of feeding poultry in modern production systems. It contains all essential nutrients and micro-ingredients to meet the requirements of the animals. Usually it is offered either as mash, crumbles or pellets. Egg production is based primarily on feeding mash or crumbles. How- ever, because of animal-welfare considerations a trend to supplement all-mash with whole grains, as was common in the past, may again become important. Broilers are mainly fed crumbles or small pellets, owing to the fact that intake and growth are enhanced compared with all-mash feeding.

Complete-diet feeding also is very common in intensive pig production, es- pecially in pig-fattening units. Pellets are often used, owing to their easy, dust- less handling, reduced separation and because intake, and thus efficiency, is often considerably increased. For lactating sows, complete diets are prefered because of the high requirement for readily-available nutrients. However, for gestating sows complete diets may provoke problems of poor satiety, if offered according to requirement.

Complete diets, in the shape of pellets or crumbles, are often used for fish farming. Extruded feeds to fit in with the feeding habits of certain fish are becoming popular.

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There is a definite trend to use complete diets, manufactured by compoun- ders, for non-ruminant herbivores, like rabbits and horses. Whilst fattening rabbits with complete pellets is quite common and practical, disturbance of the digestion can occur with does if there is a lack of coarse structure in the pelleted feed. With horses and game animals, pellets are fed as a supplement to rough- age. Feeding cobs with a coarse structure is another possibility for meeting the requirements of horses.

Complete-diet feeding to ruminants can increase nutrient intake which is important for high-producing cows and finishing beef cattle. However, a coarse structure is essential. As home-grown forage is the basal feedstuff for rumi- nants, preparation of complete diets is usually done on the farms and not by the compound industry.

The compound-feed industry tries to comply with the widely varying de- mands of the user. Standardizing the animal-production systems, as has been achieved in several countries, by concentrating animals in large units, simpli- fies the task of the compound-feed industry. The limits of these simplifications are the need to meet the requirements of the individual animal.

Supplements

As mentioned above, the exclusive feeding of compound feed as a complete diet may interfere with problems of physiology and satiety of the animals and may not be economically feasible. The energy value of industrially-manufac- tured compound feed is generally relatively high, owing to the fact that the manufacturing costs are judged by the market in relation to the cost of the energy or nutrient unit. Including high amounts of coarse-structured ingredi- ents to overcome physiological problems, as, for example, roughage in com- pound feed, is in general too costly, and often not able to compete with roughage on the farm. Thus the compound-feed industry produces a wide variety of sup- plements and pre-mixes to be added to various feed stuffs, such as cereals, by- products and forage: (1) for poultry, to be supplemented with whole cereal- grain; (2) for sows and pigs, to be fed with cereals, especially maize (kernels, cobs, whole plants, dry or silage) and/or with by-products of the dairy and meat industries (dried skim milk, dried whey and slaughter offal), sometimes also with roughage and kitchen waste; (3) for ruminants and other herbivores as supplement to forage (green or conserved as silage, hay etc.); (4) protein and mineral/vitamin pre-mixes often including the necessary additives to up- grade home-mixed and home-grown feed stuffs.

The accuracy of proportioning between supplements and pre-mixes on the one hand and other feedstuffs on the other, on the farm itself may cause some problems. It requires knowledge of the value and the intake of the basal feed.

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QUANTITATIVE IMPACT OF COMPOUND FEED

Raw materials

In the world, ruminants for milk and meat production represent 80% of the total livestock. According to Wheeler et al. ( 1981 ) cattle, buffaloes, sheep and goats consume about 68 and 78% of concentrates (grains, oil meals) and for- age, respectively, available for livestock (Table I).

The percentage of concentrates and roughage in the years 1970-1983 used for livestock in the E.E.C. countries is shown in Table II.

About 30% of the concentrates, calculated on an energy basis, were imported from outside the E.E.C. Calculated on a protein basis the percentage amounts

TABLEI

Partition of feed for livestock groups a, Wheeler et al. (1981)

Concentrates Forage

Cereals Oil meal Other Total

Cattle b 35 21 37 56 63 Sheep 2 3 7 12 15 Pig 32 28 39 10 2 Poultry c 27 45 13 7 1 Other d 4 3 4 15 19 Total 100 100 100 100 100

aBased on metabolizable energy (1979/80 data). bFor meat and milk production only. CFor egg and meat production. °Mainly draught animals.

TABLE II

Mean percentage of forage and concentrates over a period of 13 years, estimated for E.E.C. countries

Energy basis Protein basis (%) (%)

Forage • Permanent pasture 44.5 51.3 Other grassland 7.3 6.2 Maize silage 4.7 3.0 Total 56.5 60.5

Concentrates Cereals 24.8 13.1 Other marketable feedstuffs 18.7 26.4 Total 43.5 39.5

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to 56%, showing that residues of oil/seed extraction and corn gluten especially are imported. During these years, a significant trend in the increased produc- tion of maize silage and home-produced cereals and of increased importation of other marketable feedstuffs appears. The upward trend of imports of pro- tein-rich feedstuffs seems to have been broken in the last few years (1983-1985). This can, in part, be attributed to the price relationship between oilseeds and grains. On the other hand, pasture and grassland production decreased during the last 15 years, which is true for the imports of cereals because of large sur- pluses in the E.E.C.

Compound feed

The proportion of compound feed in the total feed intake is less for cattle than for pigs and poultry. Table III shows that about 50 and 70% of the rations for pigs and poultry, respectively, consists of compound feed.

In general, about 50% of the cereals produced in 10 E.E.C. countries are fed to animals. About one third of the production is used for human consumption and the rest is exported to countries outside the E.E.C. Table IV shows the estimation of the production and utilization of cereals in the year 1986/1987.

About 42% of the cereals fed to animals are processed by the compound industry. The amount of cereals in compound feed is shown in Table V.

From the data in Table V it can be concluded that a great part of compound feed consists of by-products from the food-processing industry (flour milling, oilseed extraction, meat- and fish-processing). The compound-feed industry helps, to a great extent, to recycle the offal of food processing into animal production, whilst meeting the best possible quality-price relation and main- taining at the same time the price level of the basic raw material.

The use of compound feeds by various classes of animals is shown in Table VI.

The allotment of the compound feed to the various livestock classes differs

TABLE III

Amount and proportion of compound feed in the total consumption, calculated on the basis of feed units (1 kg barley= 1 FU) in 8 E.E.C. countries

Year Cattle Pig Poultry Others Total

Mt (%) Mt (%) Mt (%) Mt (%) Mt (%)

1973 16.9 9.8 21.4 50.4 18.3 67.5 2.0 9.5 58.6 22.2 1978 24.6 14.3 25.0 53.9 19.1 68.0 3.0 11.8 71.7 26.4 1983 29.2 17.1 26.8 53.5 21.9 70.0 3.5 13.8 81.4 29.3 1984 29.5 17.4 26.7 51.0 21.1 70.4 3.7 14.0 81.1 29.1 1985 29.0 17.2 26.5 50.9 21.0 68.2 3.6 13.3 80.1 28.1

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TABLE IV

Production and utilization of cereals in 10 E.E.C. countries in Mt

1974/75 1977/78 1980/81 1983/84 1986/87"

Production 111.0 105.6 124.8 123.3 134.8 Utilization 117.8 114.9 117.7 116.4 114.1 Consumption

Human 45.3 45.2 46.9 46.2 44.8 Animal 72.5 69.7 70.8 70.2 69.3

Compounded b 28.7 30.2 29.8 29.0 Not compounded b 41.0 40.6 40.4 40.3

aEstimated. bNot stated.

TABLE V

Amount of cereals in compound feeds in 9 E.E.C. countries in Mt

1975/76 1977/78 1980/81 1983/84 1986/87"

Cereals 27.0 29.2 29.4 29.0 28.2 Other components 34.7 49.3 50.1 53.3 52.3

Total 61.7 78.5 79.5 82.3 80.5 Percent cereals 44 37 37 35 35

aEstimated.

TABLE VI --"

Compound-feed production in the year 1985 in various European countries (F.E.F.A.C., 1986)

Cattle Pig Poultry Other

Mt (%) Mt (%) Mt (%) Mt (%)

F.R.G. 7.1 43 France 3.5 24 Italy 3.9 36 The Netherlands 5.7 35 Belgium 1.4 28 U.K. 4.5 44 Ireland 1.2 60 Denmark 1.7 39 Austria 0.1 11 Switzerland 0.2 25 Portugal 0.6 25 Spain a 2.5 21

5.8 35 3.2 19 0.5 3 4.3 29 5.5 38 1.3 9 2.4 22 4.1 38 0.4 4 6.9 42 3.4 21 0.3 2 2.6 52 0.9 18 0.1 2 2.1 20 3.2 31 0.5 5 0.4 20 0.3 15 0.1 5 2.0 47 0.5 12 0.1 2 0.3 33 0.4 45 0.1 11 0.4 50 0.1 13 0.1 12 0.9 38 0.8 33 0.1 4 4.2 36 4.0 34 1.1 9

Total 32.4 32.3 26.4 4.7

Mean (x) 33 35 26 6 SD (%) 13 11 11 4

a1984.

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TABLE VII

Compound-feed production in Europe compiled from various sources a

Country Year Mt year- 1

Austria 1981 1.1 Belgium 1985 5.4 Bulgaria 1980 4.4 C.S.S.R. 1980 5.0 Cyprus 1979 0.4 G.D.R. 1980 4.5 Denmark 1982 4.6 Finland 1981 1.5 France 1983 15.4 F.R.G. 1983 17.8 Greece 1983 2.4 Hungary 1983 4.0 Ireland 1982 1.8 Iceland 1982 1.9 Italy 1983 11.2 Luxemburg 1985 0.1 The Netherlands 1986 16.5 Norway 1976 1.3 Poland 1980 4.2 Portugal 1980 3.5 Rumania 1975 4.0 Spain 1985 11.8 Sweden 1985 2.2 Switzerland 1986 1.3 Turkey 1983 2.3 U.K. 1982 11.8 U.S.S.R. 1985 70.0 Yugoslavia 1981 3.4

Total 214.0

~Personally communicated by F.E.F.A.C.; Buhler; Boucqu$; V.S.F. (1987).

considerably between the countries. This could be taken as reference to the different production specialization and feeding systems in the respective coun- tries. As a mean about one third of compound feed is processed for cattle and pig feeding, respectively, one quarter for poultry and the rest for various animal species.

A complementary estimation of total compound-feed production is shown in Table VII.

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FEED ADDITIVES

General

The inclusion of minor quantities of specific components of natural or syn- thetic origin into compound feed is a common practice in industrial nations. To prevent possible adverse effects to the animal, to human beings and to the environment, the feed additives have to be approved by the various state-reg- istration authorities. The requirements for clearance of a specific additive are based on the various national laws as well as on European and international conventions. The strictness of the requirements depends, in the main, on the type of the substance and the potential risk of adverse effects for man, animals and the environment. This policy is nowadays widely, but not always unani- mously accepted.

In general the following information on the additive concerned is required for clearance: (1) identification based on good laboratory practice; (2) chem- ical, physico-chemical and technological properties; (3) assignment of appli- cation concerning animal species as well as time and quantity of application; (4) methods of qualitative and quantitative analysis in the feed as well as of residues in the animal product, including metabolites of the substances; (5) metabolism, pharmacological and biological effects or side effects and possible toxicological effects, including mutagenicity, teratogenicity and carcinogen- icity; (6) possible hazard of build-up populations of pathogenic microorga- nisms which are resistant or cross-resistant to antimicrobial agents, indispen- sable for medical use; (7) efficiency in respect to the desired effect on the animal.

The strict and very extensive requirements for the clearance of a substance as a feed additive can be met only with laborious screening of new substances by technical specialists of all kinds. Thus the development of a new additive can take between 8 and 10 years, at great expense.

Types of additives

General Substances which are allowed to be added to compound feed in small quan-

tities can be classified in two principal categories: (1) Additives, which are essential for the maintenance of the biological func-

tions of the animals. Vitamins and trace elements are typical examples of this category. The requirements for approval of these additives are in general less severe. However, they have to be more severe if adverse effects are expected from feeding in excessive quantities or if there are traces of undesirable sub- stances in the additives which appear subsequently in meat, milk or eggs.

(2) Additives, which are not essential for the biological function of the ani- mal, but which have a specific, positive effect on the clinical healthy organism.

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Growth promoters are the most typical example of this kind of additive. Sub- stances which directly modify the hormonal or nervous regulation of metabo- lism are another example of non-essential additives.

Both categories of additives have no nutritive value per se but they improve the nutritive value of the feed and thus the performance of the animal and the efficiency of feed conversion. The inessential feed additives of the second cat- egory can be grouped as follows: technological additives; absorption enhancers; antimicrobial agents; other growth promotors; metabolic modifiers; probiotics; prophylactics.

We use this pragmatic classification, bearing in mind, that several additives could be classed with more than one group. Besides, feed additives, having a prophylactic effect, are on the borderline between nutritional and medicinal use.

The feed industry and animal nutritionists also make use of a third category of feed products, which are added in small quantities to compound feed. This group includes individual amino acids and other organic acids, propylenegly- col, urea and others. The addition of such components may be looked on as being essential for a specific production system but not for the maintenance of the biological function. Apart from propyleneglycol, which is used for feed pro- cessing reasons, they have a specific nutritive value and may enhance animal performance.

Technological additives

Preservatives. Based mostly on organic acids (e.g. propionic acid, fumaric acid) these components can reduce or prevent the development of bacterial or my- cological spoilage of feed. However, they may conceal the presence of spores and thus the possible former growth of microorganisms, which may have pro- duced toxins.

Antioxidants. Antioxidants are frequently added to protect components of the feed, which are sensitive to oxidation. They include natural or synthetic toco- pherols and lecithin as well as various synthetic products. Antioxidants are used especially to protect unsaturated fatty acids in fats and oils, Vitamin A, carotene and carotinoids.

Pelleting, free-flowing agents and dust preventives. To improve the pelleting of feeds, various agents, mostly of negligible or very low nutritive value, are added to compound feed. They include argillaceous earths as for example montmo- rillonite or various derivatives of lignosulfate and cellulose. To improve the flow characteristics of compound feeds, flowing agents (various silicates) are added.

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Flavours. Flavours are single spices or mixtures of spices, as well as synthetic aromatic compounds. They are sometimes used to conceal unattractive natural smells, tastes or structures of feed, to enhance feed intake. Opinions on the advantage of using flavours in animal production are still controversial.

Colours. For poultry and fish production, colouring agents, mostly carotinoids of natural or synthetic origin, are often added to the feed for a distinct colour- ing of the animal product, to make it more attractive to the consumer. This affects the colouring of the egg yolk, skin of broilers or meat of fish. To distin- guish clearly medicated feed from other feed colouring agents are sometimes added.

Absorption enhancers

Enzymes. The addition of proteolytic and amylolytic enzymes to the feed is sometimes done, to increase the digestion and absorption of less digestible feedstuffs. Until now, tests with various enzymes, produced by extraction from organs of animals (rennin, pancreatic juice) or from microorganisms did not prove consistent efficacy.

Emulsifiers. To reduce the particle size of fats for better digestion and absorp- tion, emulsifiers are incorporated into milk replacers. Emulsifiers are also used to administer fat-soluble vitamins to animals in aqueous solution. Natural emulsifiers such as lecithin and saponin as well as synthetic emulsifiers are customary.

Antimicrobial agents (growth promotors) Antimicrobial agents are added in comparatively small amounts to improve

daily weight gain and feed-conversion ratio of fattening animals. Two classes of antimicrobial agents may be distinguished: (1) antibiotics,

which are metabolites of living cells ( fungi, bacteria); (2) chemotherapeutics, which are chemically synthesized.

This distinction is widely accepted, although antibiotics produced by bac- teria are sometimes modified by stepwise chemical transformation. Thus sev- eral products could be allocated to either class.

Since about 1970, most authorities have striven for a clear distinction be- tween antimicrobial agents used for growth promotion and others for thera- peutic use, either for human or animal therapy. But this distinction is not strictly maintained.

The antimicrobial agents used for growth promotion are nowadays not sig- nificantly absorbed in the intestine. They are qualitatively and quantitatively effective on the microbial population of the intestine, including the rumen. This entails in principle an increased efficiency of utilisation of nutrients, al-

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though variable for various animal species and age classes. The greatest effect is observed with young animals.

The following mean improvement of the daily weight gain at a given feeding level has been estimated: (1) poultry, broiler 2-5%; (2) pigs, piglet 10-20%, weaner 5-10%, finishing 2-5%; (3) cattle, suckler calf 10-15%, bull 2-10%.

Simultaneous improvement of the feed-conversion ratio occurs. The degree of this improvement depends on the feeding level (restricted or ad libitum feeding) and the response of the animal in respect of the composition of the product (liveweight gain, milk). A wealth of literature exists on this subject.

The use of antimicrobial agents for growth promotion, with or without ve- terinarian prescription, is subject to strict regulations in all European coun- tries. As these regulations differ between countries and may be altered at short notice, the reader is referred to national authorities for precise information.

Other growth promotors

Copper. The addition of copper to pig feed in higher amounts than are neces- sary to cover its requirement as a trace element has a growth-promoting effect. Especially in feeds for young growing pigs 75-175 mg kg- 1 feed may be added. Higher amounts may be harmful to the function of the liver of the pig. Using such high amounts of copper increases the danger of pollution of the environ- ment through the manure of the pigs. Therefore a maximum level of 35 mg kg- 1 feed is applied now for growing pigs in some countries.

Metabolic modifiers Metabolic modifiers consist of substances which directly influence the cel-

lular metabolism of the animal, rather than the activity of the digestive tract, or the microbial population therein. The present generation of metabolic mod- ifiers includes hormones and hormone-like substances, as well as synthetic compounds which have a direct effect on the nervous regulation of metabolism. Steroidal hormones, of either natural (testosterone, oestradiol and progester- one), or synthetic origin (trenbolone and zeronal), have been widely used. The stilbene compounds, diethylstilboestrol, hexoestrol and dienostrol were also used at one time, but since 1981 their use has been widely prohibited. All these compounds positively affect the metabolism of growing and fattening animals, especially cattle, reducing the deposition of fat and increasing the proportion of protein in the liveweight gain. Such an effect is regarded as desirable from the human dietary viewpoint.

Because steroidal hormones are also active by mouth in humans, their use was restricted to slow-release implants of materials with lower levels of oral activity, and withdrawal periods were instigated, as well as the discarding of the site of the implant. If the recommended procedures were followed, the level of steroidal hormones detected in meat from treated animals presented no haz-

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ard to the health of the consumer (E.E.C. 1982). Nevertheless, the E.E.C. introduced a complete ban on the use of steroidal sex hormones in animal production in December 1985. The trigger for this decision was probably the evidence that withdrawal periods and procedures for the discarding of tissues in the area of the implant were not always being followed.

Research is currently in progress on growth hormone, or bovine somatotro- pin, BST, a protein hormone which is species specific and not effective by mouth, since the protein molecule is digested by the enzyme systems of the animal. BST is secreted by the pituitary gland, and has a profound influence on many bodily functions, particularly lactation, as well as growth. Milk yield increases of 2-4 kg day- 1 have been recorded, accompanied, after some delay, by an increase in feed intake to maintain energy balance. The manufacture of BST on a commercial scale is now possible, using recombinant-DNA tech- niques. The levels of the hormone in the meat and milk of treated animals are of the same order as in untreated animals, since all animals secrete the hor- mone themselves. Bovine, ovine or porcine BST are not effective for humans, whatever the route of administration.

The search for other metabolic modifiers for more profitable animal produc- tion continues, with the aim of replacing not only the steroid hormones and other directly-acting hormones, but also the antimicrobial growth promoters. Research is being directed to hormone-releasing factors and substances, which would alter the level of secretion of the hormones of the animal, or alter or depress nervous signals. As an example, the beta-agonists, Clenbuterol and Cimaterol can have such effects, but some are known to influence the cardio- vascular system or the motility of the digestive tract. Since such compounds are also active in the human, residues in meat may be a problem.

It is evident that the authorities should approve such substances only after very careful and conscientious verification of all possible harmful effects on animals, man and the environment. For the time being, it would be premature to promote the general use of substances which have a direct effect on the physiology of the animal at the cellular level, although some promising re- search results are available.

Probiotics The term 'probiotics' is used for deep-frozen bacteria which are revived if

fed to the animal. They are claimed to have a regulatory effect on the microbial micro flora. Their effect on growth promotion is until now not clearly proven. They may have a certain impact on the reconstitution of the intestinal micro- flora after antibiotic treatment.

Prophylactics According to official regulations, only agents to prevent coccodiosis in poul-

try and rabbits may be used as prophylactic feed additives. However, the use

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of antimicrobial agents in slightly higher dosages than those effective for growth promotion is often claimed to have a disease-preventing effect. This is often debated between veterinarians and nutritionists, bearing in mind tha t some antimicrobial agents are also effective against protozoa.

REFERENCES

E.E.C., 1982. Interim Report of the Scientific Working Group on Anabolic Agents in Animal Production, No. 2924/IV/82.

F.E.F.A.C., 1986. Statistical Yearbook, European Federation of Compound Animal Feedingstuffs Manufacturers, Brussels.

Wheeler, R.O. et al., 1981. The World Livestock Product, Feedstuff and Food Grain System. Win- rock International, Morrilton, AR, U.S.A.