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Breeds of Livestock, Department of Animal Science

Breeds of Livestock: Comparitive Research Section: Breed Comparisons in the Germplasm Evaluation Program at MARC

Breeds of Livestock: Comparitive Research Section: Breed Comparisons in the Germplasm Evaluation Program at MARC

Breed Comparisons in the Germplasm Evaluation Program at MARC

Larry V. Cundiff, Ferenc Szabo , Keith E. Gregory, R. M. Koch,
M. E. Dikeman , and J. D. Crouse

Agricultural Research Service
U.S. Department of Agriculture
Roman L. Hruska U.S. Meat Animal Research Center
Clay Center, Nebraska 68933

Introduction

Breed differences in performance characteristics are an important genetic resource for improving efficiency of beef production. Diverse breeds are required to exploit heterosis and complementarity through crossbreeding and new composite breeds and to match genetic potential with diverse markets, feed resources and climates. This report presents results from the Germplasm Evaluation Program at the Roman L. Hruska U.S. Meat Animal Research Center (MARC) to characterize breeds of cattle representing diverse biological types for bioeconomic traits that influence quantity and value of production.

 

Germplasm Evaluation Program

Table 1 shows the mating plan for the first four cycles of the Germplasm Evaluation Program. Topcross performance of 26 sire breeds have been evaluated in F1 calves out of Hereford, Angus or crossbred dams. Hereford-Angus reciprocal crosses were produced in each cycle of the program. Some of the Angus and Hereford sires used in cycle I, were repeated as reference sires in cycle II, III and IV to provide ties for analysis of data pooled over all four cycles.

In cycle I, 32 Hereford (Horned and Polled), 35 Angus, 33 Jersey, 27 South Devon, 20 Limousin, 26 Charolais, and 27 Simmental sires were used by artificial insemination (AI) to produce progeny in 1970-1972. In cycle II, 16 of the Angus sires and 16 of the Hereford sires (reference sires repeated from Cycle I) and 16 Red Poll sires, 11 Brown Swiss sires (7 imported Braunvieh sires from Switzerland, 4 domestic), 11 Gelbvieh, 18 Maine Anjou, and 20 Chianina sires produced progeny in 1973-74. In cycle III, 13 Hereford and 14 Angus sires (reference sires repeated from cycle I) and 17 Brahman, 6 Sahiwal, 9 Pinzgauer, and 7 Tarentaise sires produced progeny in 1975-1976. In Cycle IV, semen from 14 Angus and 11 Hereford (reference sires repeated from Cycle I, born from 1963-1970), 30 current Angus (born 1982-1984), 32 current Hereford (14 horned and 18 Polled, born 1982-1984), 29 Longhorn, 24 Piedmontese, 31 Charolais, 29 Salers, 31 Galloway, 22 Nellore, and 26 Shorthorn bulls produced progeny in 1986-1990. About 200 calves were produced by each sire breed. In cycle IV, following an AI period of about 45 days, one or two bulls each of Charolais, Gelbvieh, and Pinzgauer breeds were used each year by natural service in single-sire breeding pastures for about 21 days. These breeds were used in clean-up matings to increase ties to previous cycles and facilitate pooling of results over all four cycles.

Calves were born in the spring, beginning in March each year. Male calves were castrated within 24 hours of birth. Calves were creep fed (usually whole oats) from mid July or early August until weaning, usually in October (except in September, 1974 due to drought conditions). Following a postweaning adjustment period of about 25 to 40 days, steers were fed separately by sire breed in replicated pens for about 200 days. Averaged across years and feeding periods, the diet contained 1.27 MCal ME/lb, 12.8% crude protein, and 9.2% digestible protein. Representative samples of steers were slaughtered serially each year, in 3 to 4 slaughter groups spanning 56 to 84 days. The steers were slaughtered in commercial packing plants. Hot carcass weights were obtained and used to estimate dressing percent (100 X carcass weight/final live weight). After a 24-hour chill, USDA yield grade (fat thickness, ribeye area, estimated % kidney fat) and quality grade (marbling, maturity) data were obtained. The right side of each carcass was fabricated into boneless, retail product (including all steaks, roasts and lean trim {trimmed to 25% fat basis}), fat trim, and bone. Retail product, fat trim, and bone from the right side was doubled to estimate retail product yield from the carcass in terms of weight and as a percentage of cold carcass weight.

All F1 females were retained to evaluate growth, age at puberty, reproduction and maternal performance through mature ages. Heifers, managed to be bred as yearlings and calve first at 2 years of age, were fed a diet of approximately 50% corn silage and 50% alfalfa or grass haylage plus protein or mineral supplement. Estrus was checked visually twice daily from an average age of about 250 days until the middle of the breeding season at about 420 days of age. Date at puberty was defined as date at first observed estrus confirmed by a subsequent estrus observed within 45 days. Females were mated to produce three-breed cross progeny. In cycle I, females were bred by AI to Hereford, Angus, Devon, Holstein and Brahman bulls to produce their first calves as 2-year-olds, by AI to Hereford, Angus, Gelbvieh, Maine Anjou, and Chianina sires to produce their second calves as 3-year-olds, and by natural service to Brown Swiss sires for their subsequent calves. In cycle II, females were bred by AI to Hereford, Angus, Santa Gertrudis and Brahman bulls to produce their first calves as 2-year-olds, and by natural service to Simmental sires for their subsequent calves. In cycles III and IV, females were bred by natural service to Red Poll sires to produce their first calves as 2-year-olds and to Simmental sires to produce subsequent calves through at least seven years of age.

Data from two-breed F1 crosses (Phase 2 progeny out of Hereford and Angus dams, Table 1) were analyzed with mixed model procedures (Harvey, 1985) considering appropriate fixed effects (e.g., birth year, cow age, sex, breed of sire, breed of dam, and breed of sire X breed of dam) and random effects (sire nested within breed of sire to test breed of sire and residual variance to test other fixed effects). Data for Devon, Brangus, Santa Gertrudis, and Holstein crosses (phase 3, three-way crosses out of F1 dams, Table 1) were pooled with data from the separate analysis for two-breed F1 crosses by adding the average difference from contemporary Hereford and Angus sired three-way crosses to the mean of Hereford-Angus reciprocal F1 crosses from the pooled analysis of phase 2 progeny.

Breed group means are presented for F1 crosses grouped into seven biological types based on relative differences (X lowest, XXXXXX highest) in growth rate and mature size, lean-to-fat ratio, age at puberty and milk production (Table 2). Although straightbred Hereford and Angus were produced, their results are not presented because they did not have the benefit of heterosis. Thus, breed group means for all traits are for F1 crosses that benefit from effects of heterosis, averaged over both Hereford and Angus dams. Means for current samples of Hereford, Angus and Charolais sires (sires born since 1983) are estimated separately from those by original sires (born in 1970 or earlier).

 

Results

Breed group means are presented in Table 3 for gestation length, unassisted births (for cows calving at 4 years of age or older), calf survival from birth to weaning, birth weight and 200-day weaning weight. Data for unassisted births are for cows calving at 4 years of age or older to conform to cow ages available in all cycles. This was necessary because cow age X breed of sire interaction effects were significant for unassisted births in analysis of cycle I data and no 2-year-old cows were included in cycles II, III and IV and no 3-year-old cows were included in cycles II and III of the program. There were significant differences among breeds for all birth and weaning traits. Breeds with the heaviest weights at birth and weaning tended to have more calving difficulty than those with lower growth potential. Calf survival tended to be lower in breeds requiring more assistance at birth.

Breed group means for postweaning average daily gain, final weight, dressing percent, marbling score (slight = 400 to 499; small = 500 to 599) and percentage grading USDA Choice or higher are shown in Table 4. Breed group means for carcass weight, fat thickness, rib eye area, and kidney-pelvic-heart fat percentage (estimated and actual) are presented in Table 5. Breed group means for retail product, fat trim and bone presented as a percentage of carcass weight are presented in Table 6. Weight of retail product, fat trim and bone adjusted to the average slaughter age of 450 days are also presented in Table 6. There were significant differences among all sire breeds for carcass and meat traits. Breeds that ranked highest for percentage retail product tended to have lower levels of marbling. Progeny by current sires versus progeny by original sires of the Hereford and Angus breeds indicate that live weights and retail product, fat trim and bone weights have increased significantly at a constant age. However, carcass composition (retail product, fat trim and bone expressed as a percentage of carcass weight) and other carcass traits have not changed in Herefords and Angus between the late 1960's and the mid 1980's.

Breed group means are presented in Table 7 for 400-day and 550-day weight, percent expressing puberty, age at puberty, and pregnancy rate. Actual age at puberty is for heifers expressing a first estrus (ranging from 58.5 to 100%). Adjusted age at puberty is adjusted to a 100 percent expression basis assuming an underlying normal distribution. Breed group means differed significantly for all growth and puberty traits of heifers. Heifers sired by bulls of breeds with large mature size (e.g., Charolais, Chianina) tended to be older at puberty than heifers sired by bulls of breeds with smaller mature size (Hereford, Angus). However, the relationship between mature size and age at puberty can be offset by associations with milk production. Breeds which have been selected for milk production reach puberty earlier than breeds of similar mature size and lean growth potential that do not have a history of selection for milk production (e.g., Braunvieh, Gelbvieh, Holstein, Simmental, and Salers versus Charolais and Chianina). Also, the Bos indicus breeds (Brahman, Sahiwal, and Nellore), which were older than all other breeds in age at puberty, appear to have been subjected to selection pressures that set them apart from Bos taurus breeds for age at which they exhibit their first estrus. Although age at puberty differed significantly among breeds, conception rate in yearling heifers did not differ consistently between breed groups reaching puberty at the oldest ages from those breed groups reaching puberty at the youngest ages. For example, conception rate of Brahman and Sahiwal cross heifers was very high in spite of their older age at puberty. Heifers in all breed groups were grown and developed under dry lot conditions on a moderately high energy diet (about 1.0 Mcal metabolizable energy [ME] per lb) and conception rate was not limited by variation observed among breed groups in age at puberty. Heifers developed more slowly on diets with lower energy density, have been shown to exhibit puberty at significantly older ages and have lower conception rates when exposed to breeding as yearlings than heifers developed more rapidly.

Breed group means for reproduction and maternal traits of F1 females are shown in Table 8. It should be emphasized that results for females produced in cycle IV of the program are preliminary (i.e., females born in 1990 have only been evaluated as 2-year-olds, females born in 1989 have been evaluated as 2- and 3-year-olds, females born in 1986 have been evaluated as 2- through 6-year-olds). Means for traits such as conception rate, percentage calf crop born and weaned, and percentage calvings unassisted are likely to change as additional data accumulate. The relationship between birth weight and unassisted calvings is much lower when evaluated as a maternal trait in F1 daughters than when evaluated directly in F1 progeny (Table 3) of diverse breeds. For example, progeny of Chianina, current Charolais, Salers, Maine Anjou, Braunvieh, and Shorthorn dams were relatively heavy at birth but above average in unassisted births. Also, progeny of Hereford-Angus cross females by current sires were heavier than those by original sires but calving assistance was similar. Females by Bos indicus sire breeds (Brahman, Sahiwal and Nellore) and by Jersey and Longhorn sires had progeny with relatively light birth weights and excelled in calving ease. Breed group differences in weaning weight of progeny are strongly associated with genetic potential for growth and milk production of the diverse biological types.

No one breed excels in all traits that are important to beef production. Crossbreeding systems that exploit heterosis and complementarity and match genetic potential with market targets, feed resources and climates provide the most effective means of breeding for production efficiency.

 


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