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R e f e r e e d

PROTEIN, ENERGY AND DRY MAI"I'ER CONSUMPTION BY RACING THOROUGHBREDS:

A RELD SURVEY

Kenneth Gallagher, DVM, MS, 1 John Leech, BS, M A 2 and Howard Stowe, DVM, PhD 1

SUMMARY

A field survey involving 109 horses in 9 stables at a Detroit racetrack was conducted to determine feeding prac- tices and to estimate crude protein (CP), digestible energy (DE), and dry matter (DM) consumption by racing Thorough- breds, and to compare those intakes with 1989 recommenda- tions of the National Research Council (NRC), "Nutrient Requirements of Horses." Trainers were interviewed regard- ing: 1) the age and sex of the homes; 2) their feeding practices; and 3) the horse's training and racing schedule. Only adult homes who were actively racing and continuously stabled at the track were included.

Body weights (BW) were estimated using a chest girth measurement. The horses had an overall mean body condition score of 5 which indicated average body condition for a racing

Authors' addresses: 1Department of Large Animal Clinical Sciences, Col- lege of Veterinary Medicine, Michigan State University, East Lansing, MI 48824; 2Cooperative Extension Service, Michigan State University, East Lansing, MI 48824. Acknowledgments: This study was partially funded by a grant from the Cooperative Extension Service, Michigan State University. Appreciation is expressed to the Ladbroke Detroit Racetrack management, the Michigan Division - Horsamen's Benevolent and Protective Association, the Michigan United Thoroughbred Breeders and Owners Association, racetrack veteri- narians, owners, trainers, and grooms who assisted in this survey. Special thanks to Maryellen Shea for computer assistance.

Thoroughbred at this track. Feed samples of hay and concen- trate from each stable were weighed and analyzed at a commercial laboratory to determine CP, DM, acid detergent fiber (ADF), and estimated energy density. A computer program calculated CP, DE, and DM values for each horse's ration based on amounts fed. The software program included with the 1989 NRC publication was used to compare esti- mated nutrient intakes with current NRC recommendations for a horse of a given BW.

Trainers fed a variety of hays. Eight trainers fed oats and only one fed corn. All trainers fed commercial sweet feeds. The mean total amount of feed for all homes on an "as fed" basis was 13.7 kg. The mean estimated DM intake for all horses was 12.3 kg vs. NRC recommended 11.6 kg. The mean for percentage of roughage in the ration for all stables was 53% vs. a NRC recommendation of 35%. The mean CP% on a DM basis for all stables' rations was 13.8% vs. a NRC recommendation of 11.4%. The means for actual CP and DE intakes for all horses were 1678 g and 33.3 Meal compared with current NRC recommendations of 1324 g CP and 33.1 Meal DE.

Protein amounts were above those recommended due to the common practice of feeding relatively higher CP% in the rations than necessary for racehorse performance. These data appear to be more consistent with the recommendations of NRC in 1989 than previous recommendations in 1978.

Volume 12, Number 1, 1992 43

I N T R O D U C T I O N

The most recent (1989) edition of the National Research Council (NRC) publications, "Nutrient Requirements of Horses, "~ e contains revised recommendations for race horses in the intense work category, specifically in the areas of crude protein (CP), digestible energy (DE), and dry matter (DIVI) intake. Previous surveys z'~s indicated the energy needs of working Standardbreds and Thoroughbreds were signifi- cantly underestimated in the 4th (1978) edition of the NRC, "Nutrient Requirements of Horses. "~ 1 The 1978 NRC require- ments ~ for working horses were based on studies with polo ponies and did not reflect the strenuous work schedules of race horses or the unique stress factors affecting horses in a racetrack environment.

Since the 1978 NRC publication, ~ studies and surveys have been conducted to determine the energy needs of race horses based on their activity. ~,4.s. ~.~o.~ These studies and surveys were used in part to revise the DE requirements for horses in the intense work category to as much as 100% above maintenance levels.

Other studies since 1978 focused on the protein needs of working horses, a.~ It is concluded at this time that protein requirements should be maintained at a ratio compared to DE, with the race horses consuming 40 grams of CP/Mcal of DE. While the 1989 edition of the NRC ~2 has addressed these issues, there is still apaucity of information on the CP, DE, and DM consumption by horses following a regular training and racing program at major racetracks.

The following field survey was conducted to determine feeding practices at Thoroughbred racing stables. Estimates were made of the CP, DE, and DM consumption by racing Thoroughbreds, and compared with the current recommenda- tions of the NRC. ~2

M E T H O D S

The survey was conducted during the summer racing season of 1987 at the Ladbroke Detroit Racecourse. Nine trainers and 109 horses were involved in the survey. Trainers were interviewed regarding: 1) the age and sex of the horse; 2) their feeding practices; and 3) the horse's training and racing schedule. Only horses 3 years-of-age or more were used in the study so nutrient intake would represent require- ments for maintenance and work but not growth. The horses

Table 1. Typical training and racing schedule for Thorough- brads at 9 racing stables based on a 14-day period.

Days 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Gallop 2 x x x x x x x x

Walk I - Walk 45 minutes. Gallop 2 - Warm up 2 furlongs at a slow gallop in I minute, gallop 12 fudongs in 3 minutes 10 seconds, and walk 45 minutes (includes walking to and from the track). Breeze 3- Warm up 6 fudongs at a slow gallop in 3 minutes, breeze 4 furlongs in 54 seconds, and walk 50 minutes (ineludas walking to and from the track). Race 4 - Warm up 8 fudongs at a slow gallop in 4 minutes, race 6 furlongs in 1 minute 12 seconds, walk 60 minutes (includes walking to and from the track).

Table 2. Mean body condition scores for Thoroughbreds at 9 racing stables. 1

Overall Stable 1 2 3 4 5 6 7 8 9 Mean

Mean score 4 5 5 6 5 5 5 5 5 5 1Based on Henneke, et al. s

were continuously stabled at the track. All stables followed training schedules typical for this racetrack, but adjusted the schedule as needed for the individual horse.

The horses were actively racing at least every 2 weeks. Body weights (BW) were estimated from chest girth (CG) measurements in inches taken with an 8 ft. non-stretch fabric tape. One person took the measurements for uniformity of technique. The CG measurement was included in an equation that factored in the sex of the horse to arrive at an estimated BW: male lbs. = (.14475 x CG), a female lbs. = (.14341 x CG). 3 Each horse was observed, palpated, and assigned a body condition score (Table 2) based on the 1-9 point system by Henneke, et ais Mean ages and BWs of the horses were calculated for each stable.

The estimated daily feed intake for each horse was weighed, and samples of the hay and concentrates were tested at a commercial laboratory, a The samples were analyzed for DM, CP, and acid detergent fiber (ADF). The DE values were estimated based on theADF content. Because of hay variabil- ity, two samples were tested from each stable, and the results were averaged together to allow better estimates of the nutrient availability from the roughage portion. A 5% waste

aMontrose Feed Laboratory, 6200 Willard Rd., Birch Run, MI 48415. bVan Saun, Spartan Equine Ration Evaluator, Michigan State University, East Lansing, MI 48824, (1990).

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...... j 2

Table 3. Age, bodyweight (BW), ration composition and nutrient density data for Thoroughbreds at 9 racing stables.

Concentrate Hay (kg as fed)/day (kg as fed)/day

Est. Mean Mean Age BW Total (yrs) (kg) Mixed (kg as Roughage

Stable N ± SD -+ SD Grass Mixed Alfalfa Grain t Oats Corn fed)/day %

1 9 3.5 490 -+.42 ---34

2 8 6.9 521 ±2.90 ±11

3 14 4.4 489 ± 1.53 __ 28

4 6 3.6 472 ±.47 ±22

5 9 4.0 548 ±1.15 ±57

6 15 4.5 506 ±1.59 -+33

7 24 4.7 489 -+1.77 -+48

8 6 4.3 511 -+1.37 -+40

9 18 6.3 533 *_.2.90 -+42

4.1

10.9

8.2

8.2

7.3

41 11.

2.3

3.6 10.0

6.4 52

2-0

3.9 12.3

7.3 57

1.3

3.8

.6 12.9

62

1.4

5.5 17.8

57

1.4

4.8 14.4 |l

50

1.3

5.5 14.7

60

1.0

4.4 13.6

8.2 55

3.9

3.0 15.1

5.5 45

6.8 12.3

Nutrient Density (DM Basis)

DE ~Mml/kr,)

DE of Total CP% (Mml/~ Ration

11.8 2.16

15.7 3.45 2.81

13.3 3.19

18.7 2.29

15.7 3.45

13.3 3.19 2.74

18.1 2.29

15.7 3.45

13.3 3.19

2-70 10.4 3.87

13.4 2.26

16.1 3.56 2.65

13.3 3.19

12.0 2.16

15.7 3.45

2.63 13.3 3.19

13.0 2.16

15.0 3.70

13.3 3.19 2.74

9.0 1.98

15.7 3.45

13.3 3.19 2.48

14.0 2-16

15.7 3.45

13.3 3.19 2.69

16.0 2-48

10.4 3.61 3.08

Mean 12 4.8 506 8.2 7.6 6.9

± SD 2.17 45

1Commercial sweet-feed mixes.

2.4 18 .6 133

m

53 13.8 2.72

Volume 12, Number 1, 1992 45

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Table4. Comparisonofdaily actual and NRC-recommended 1DMintakes byThoroughbredsat9racingstables.

DMIntake$ Estimated

Mean Actual NRC NRC Weight Hay Concentrate Total Recommended Recommended

Stable N 0tg) 0tg) (kg) (kg) (kg) % of BW % of BW

1 9 ~ 0 3.7 5.3 9.0 11.3 1 . ~ 2.31 2 8 521 5.8 5.3 11.1 12.0 2.13 2.29 3 14 489 6.6 5.1 11.7 11.3 2.39 2.31 4 6 472 9.8 6.1 15.9 10.9 3.37 2.31 5 9 ~ 8 7.4 5.4 12.8 12.5 2.34 2.29 6 15 506 6.5 6.6 13.1 11.6 2.59 2.30 7 24 4 ~ 7.4 4.8 12.2 11.3 2.49 2.31 8 6 511 7.4 6.1 13.5 11.7 2 . ~ 2.30 9 18 533 5.0 6.1 11.1 12.2 2.08 2 . ~

12 506 6.6 5.6 12.3 11.6 2 . ~ 2.30 M e ~ ± S D 45 1.7 0.6 1.9 . ~

tNRC 1989, t2

factor was subtracted from the amount of hay fed. The amount of waste was estimated by collecting and weighing discarded hay after the feeding period.

A computer program, b was used to calculate the amounts of total DM, CP and DE in each horse's ration based on the amounts fed and the laboratory results. The rations within the stable were averaged to arrive at the nutrient intake for the average horse. The software program from the NRC publica- tion la was used to compare the nutrient intake of the average horse (based on estimated BW) with current NRC recommen- dations, la

R E S U L T S

The number of horses per trainer varied from 6 to 24 per stable, with a mean of 12 per stable. The mean ages of the horses in the 9 stables varied from 3.5 to 6.9 years, and the mean age of all horses was 4.8 years. The mean BWs of the horses per stable ranged from 472 kg to 548 kg with an overall mean of 506 kg. As indicated in Table 2 the mean body condition score for all horses was 5, with horses in Stable 1 having a mean body condition score of 4, and horses in Stable 4 having a mean body condition score of 6. Estimated amounts of hay and concentrates fed are given in Table 3. Four trainers fed a grass-alfalfa mixture of hay, four trainers fed only alfalfa as the roughage, and one trainer fed only timothy hay as the roughage. Eight trainers fed oats separately as part of the ration, and only one trainer fed corn separately. All stables used commercially prepared sweet feeds in varying amounts in the daily ration. Based on the interviews with the

trainers, all stables used some form of electrolyte and/or vitamin supplementation, either orally or by injection. These supplements are not included in the tables because they were not considered to affect the CP, DE or DM consumption by horses.

On an "as fed" basis, the estimated total amounts of feed per horse ranged from 10.0 kg to 17.8 kg per day, with a mean of 13.7 kg. The estimated percentage of roughage in the ration varied from a low of 41% to a high of 62%, with an overall mean of 53%. The ratio of concentrate to roughage in this study based on the overall stable mean was .89 to 1. The estimated mean CP percentage in the rations (DM basis) by stable varied from a low of 10.9 % (Stable 1) to a high of 16.5 % (Stable 2). The mean for all stables was 13.8% CP.

The estimated DE of the total rations used at various stables varied from a low of 2.48 Mcal/kg (Stable 5), to a high of 3.08 Mcal/kg (Stable 9). The mean for all stables was 2.72 Meal/kg.The ratios of concentrate to hay, and the total amount fed on a DM basis, varied for each stable, as did the DM as a percentage of BW. The means for total amount fed, (12.3 kg), and the DM as a percentage of BW, (2.43%), are compared with 1989 NRC recommendations in Table 4. Amounts of actual CP and DE for each stable and the mean for the group are presented in Table 5, and the values are compared with 1989 NRC recommendations, la The overall means of the horses' intake of actual CP and DEwere 1678g and 33.3 Mcal, respectively.

D I S C U S S I O N

Based on interviews with trainers, information was re-

46 EQUINE VETERINARY SCIENCE

Table 5. Comparison of daily actual and NRC 1 recommendations of CP and DE intakes by Thoroughbreds at 9 racing stables.

Crude Protein Intakes Digestible Energy Intakes Estimated

Mean NRC Dlff between Diff. between Weight Actual Recommended Actual and NRC Actual NRC Recommended Actual and NRC

Stable (kg) (g) (g) (g) (g) (Meal) (Ucal)

1 490 1179 1284 -105 25.3 32.1 -6.8 2 521 1824 1360 464 30.5 34.0 -3.5 3 489 1864 1282 582 31.6 32.1 -.51 4 472 2155 1243 912 42.2 31.1 11.1 5 548 1638 1424 214 33.7 35.6 -1.9 6 506 1765 1324 441 35.9 33.1 2.8 7 489 1329 1283 46 30.3 32.1 - 1.8 8 511 1928 1335 593 36.3 33.4 2.9 9 533 1420 1389 31 34.2 34.7 -.50

Mean 506 1678 1324 354 33.3 33.1 .2 ± SD 45 314 4.73

1NRC 1989. TM

Table 6. Comparison of actual bodyweight (BW) to estimated BW from chest girth (CG) measurement.

Horse # Age Sex Actual Est. CG Difference (yrs) Sex (kg) (kg) (kg)

1 3 M 469 463 6 2 3 M 447 442 5 3 3 G 461 464 7 4 3 S 502 495 7 5 4 G 492 469 3 6 4 G 507 501 6 7 4 M 487 480 7 8 5 G 524 516 8 9 6 G 495 487 8 Mean ± SD 487 ± 24 481 ± 24 6.3

Unpublished data.

corded on the age and sex of each stable's horses 3 years-of- age or older, their feeding practices, and each horse's training and racing schedule. There was some difference in mean body condition scores between stables, but most horses had a score of 5 which was average for this group of horses (Table 2). All trainers followed feeding practices and training and racing schedules (Table 1) typical of Thoroughbred racing stables at this racetrack. Training schedules were modified for indi- vidual stables with variations in the number of gallop work- outs per week and the time at which they worked certain distances. As an example, the horses in Stable 1 galloped 12 furlongs in 3 minutes five days per week, and the horses in Stable 4 galloped 12 furlongs in 3 minutes 15 seconds three days per week. The mean age of all horses (4.8 yrs.) and the mean BW of all the horses (506 kg) were somewhat higher

than observed by Winter 15 at a Thoroughbred racetrack. The mean BW for all the horses is within the normal range of 408- 544 kg. 2

All the horses had been actively racing for 2 months, were continuously stabled at the racetrack, and therefore, were subject to stresses present in a racetrack environment. Although there is no hard data, some authors 7,1s have sug- gested these unique stresses might partially account for higher energy requirements for race horses compared to other work- ing horses.

While use of a scale would have given the most accurate BWs, the tape values are believed to be within .6-1.6% (under) the actual BWs. This interpretation is based on an unpublished survey (Table 6) by the authors at a training farm where the CGs of 9 race horses were measured and the estimated BWs were compared with actual BWs on a certified platform scale. Averaging the data from each horse in order to arrive at a stable average for age, BW, and feed intake, is an acceptable method practiced in other racetrack suryeys. 7,1s The mean estimated feed intake for all horses on an "as fed" basis was 13.7 kg. Adjusted for mean estimated BW, this feed intake was slightly lower than observed by Winter? s The mean estimated per- centage of roughage in the ration on an "as fed" basis was 53 %. The ratio of concentrate to roughage was therefore .89 to 1. Currently, NRC recommends TM proportions of 65% concen- trate and 35% roughage in the ration, for a ratio of 1.86 to 1.

All trainers except one (Stable 7 fed grass hay only) fed a higher estimated average CP percentage on a DM basis in their rations than recommended. The estimated average CP percentage for all feeds at the 9 stables was 13.8% compared to the 1989 NRC recommendation 12 of 11.4% for horses in the

Volume 12, Number 1, 1992 47

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......

intense work category. The CP percentage was higher than necessary and would at least increase the cost of the ration.

The DE values which were estimated from the ADF content of the feeds varied in the rations as indicated in Table 3. They varied from 2.48 to 3.08 Mcal/kg within the 9 stables, with an overall mean of 2.72 Mcal/kg. The current NRC recommended nutrient density for race horse rations on a DM basis is 2.85 Mcal/kg. +2 While the DE concentrations in the rations of horses in training were lower than expected, overall the horses' DM intake (as indicated in Table 4) was sufficient to maintain body condition. The overall estimated means of DM intake and the DM intake as a percentage of BW were slightly higher than 1989 NRC recommendations, +2 but lower than other surveys. ++,1 s It is possible horses could be consum- ing higher percentages of roughage in the rations (which has a relatively lower DE level than concentrates) and still meet the NRC recommendations for DM intake, but not be con- suming adequate DE. The mean actual CP intake for all stables (1678 g) is higher than NRC recommendations (1989) 12 of 1324 g, but lower than two other surveys. 1 +. + s The fact that all stables except one were above the actual CP intake requirements suggested by NRC (1989) +2 (some as high as 2.5-73% above) is a reflection that most stables were using rations relatively higher in CP on a percentage basis than NRC recommends. On the basis of this survey, overfeeding of protein is a common practice at racetracks, and more investi- gations with working horses are needed to determine the utilization of energy from excess protein.

The overall mean of the actual DE intake (33.3 Meal) was comparable to both NRC recommendations (1989) +2 of 33.1 Meal and a German study. +6 The amounts were lower but greatly different than other surveys done at Thoroughbred racetracks.l+.+ 5

Averaging in Table 5 tends to hide the fact that horses at six stables were below the NRC recommended (1989) +2 DE intakes, but still had an overall mean body condition score of 5. This could be accounted for by closer analysis of small differences in training schedules which might reveal less intense workloads.

C O N C L U S I O N S

Considering the data in this survey, it appears that the 1989 NRC recommendations 12 for CP, DE, and DM intakes by horses in the intense work category are more accurate estimates of the nutrient needs of Thoroughbred race horses than recommended in the 1978 edition. 1+ Nevertheless, ad- justments in recommendations to trainers may be necessary

because of varying training methods between stables and the differences found in horses, especially when considering individual metabolism, temperament, and the ability to handle stresses in a racetrack environment.

R E F E R E N C E S

1. Burton, JH, MacNeil S: Trainer feeding practices and nutrient intakes of Standardbreds at three Ontario racetracks. Proceedings 9th Equine Nutr Physiol Soc Symp, Michigan State University, East Lansing, MI, p51,1985.

2. Evans JW: Horses, a Guide to Selection, Care and Enjoyment, W. H. Freeman and Company, p109, 1981.

3. Freeman DW, Potter GD, Schelling GT, Kreider JL: Nitrogen metabolism in mature horses at varying levels of work. J Amin Sci 66:407,1988.

4. Glade MJ: Nutrition of the racehorse. Equine Vet J 15:31,1983.

5. Henneke DR, Potter GD, Kreider JL, Yeates BF: Rela- tionship between condition score, physical measurement, and body fat percentage in mares. Equine VetJ 15:371-372,1983.

6. Hinkle DK, Potter GD, Kreider JL, Schelling GT, Ander- son JG: Nitrogen balance in exercising mature horses fed varying amounts of protein, Proceedings 7th Equine Nutr Physiol Soc Syrup, Warrenton, VA, p91,1981.

7. Ignatoff J, Hintz HF: A survey of feeding practices at two Standardbred racetracks. Feetstuff 52(41):24,28,1980.

8. Minieri L, Barbieri V, Nizza hA: Alcuni aspetti dell' alimen- tazione del cavallo trottatore in attivita agonistica in compania. Ati Soc Ital Sci Vet 39:462,1985.

9. Mullen PA, Hopes R, Sewelh The biochemistry, hematol- ogy, nutrition and racing performance of two-year-old Thorough- breds throughout their training and racing season. Vet Rec 104:90,1979.

10, Nash R, Hintz HF: Feeding practices attwo Standerdbred tracks. Hoo/beats 49(9):23,1981.

11. National Research Council: Nutrient Requirements of Horses, 4th ed., National Academy Press:Washington, DC, 1978.

12. National Research Council: Nutrient Requirements of Horses, 5th rev. ed., National Academy Press:Washington, DC,1989.

13. Smith FH: Nutritional aspects associated with poor per- formance in the racehorse. Irish VetJ 40:87,1986.

14. Schils S, R. Jordan: Nutrition practices and philosophies of racehorse trainers: survey. Proceedings 11th Equine Nutr Physiol Soc Syrup, Oklahoma State University, Stillwater, OK, p238,1989.

15. Winter LD, Hintz HF: Feeding practices et two Thorough- bred racetracks. Proceedings 7th Equine Nutr Physicl Soc Symp, Warrenton, VA, p36,1981.

16. Zmija G, Kienzle E, Meyer H: Feeds and feeding in German training stables of racehorses. Proceedings 12th Equine Nutr Physiol Soc Syrup, University of Calgary, Alberta, Canada, p85,1991.

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