|Chase, Chadwick - Chad|
|Hammond, Andrew - Andy|
Submitted to: Beef Cattle Short Course Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2002
Publication Date: 5/1/2002
Citation: Chase, C.C.,Jr., Riley, D.G., Hammond, A.C., Olson, T.A., West, R.L., Johnson, D.D., Coleman, S.W. 2002. The search for a combination of carcass and productivity traits in Brahman cattle. 51st Annual Beef Cattle Short Course Proceedings, University of Florida, Gainesville. p. 98. Interpretive Summary: The Brahman breed is established as the breed of choice for providing adaptation to warm climates in the U.S. However, a persistent criticism of Brahman crossbred cattle is that they have lower carcass quality grades and more variable tenderness than many other breed types. This has resulted in significant discounts in the market place for Brahman-type calves. If within breed selection could improve carcass traits such as marbling score, USDA quality grade, and(or) tenderness, cow-calf producers would be able to address industry concerns for these traits and continue to benefit from the excellent performance of crossbred Brahman cows without receiving discounts for calves at marketing. Therefore, feedlot performance and carcass data were collected from 504 Brahman calves produced from 22 different Brahman bulls over a 5 year period to assess the heritability or extent of genetic control of these traits in Brahman cattle. Moderate to high values for heritability were observed for most carcass traits including marbling score and USDA quality grade. This indicates that effective selection programs for these traits could be implemented. In contrast, low heritability values were observed for tenderness traits. Although this does not exclude improvement in tenderness by selection, it does indicate that it may be a longer and more difficult process. Additionally, for each bull predicted breeding values for each trait were estimated. This allows bulls to be compared to one another for a given trait. For example, predicted breeding values for USDA quality grade were 61.1 for sire 13 and -32.4 for sire 10. This indicates that a large number of calves from sire 13 would be expected to have about a one-half higher USDA quality grade than calves from sire 10. Although predicted breeding values are never estimated perfectly those with higher accuracies are expected to be more reliable. These results suggest that carcass traits such as marbling score and USDA quality grade would be responsive to selection in the Brahman breed, but that for tenderness traits selection would likely be slow and should be complemented by the use of post slaughter technologies to enhance tenderness. Predicted breeding values for the sires used in this study could be used as a tool to guide selection for enhanced production, carcass quality, and tenderness in Brahman cattle.
Technical Abstract: The objectives of this study were to use progeny testing to estimate the heritabilities for carcass and tenderness traits in the Brahman breed and to predict breeding values for these traits in Brahman bulls. Feedlot and carcass data from 504 Brahman calves (258 heifers and 246 steers) sired by 22 Brahman bulls were collected over 5 years (1996 to 2000). The average number of progeny per sire was 22.9 and ranged from 7 for a sire used in 1996 (this bull was injured early in the breeding season) to 50 for a sire used in 1998 and 1999. Restricted maximum likelihood procedures of MTDFREML were used to estimate heritabilities and to calculate predicted breeding values and standard errors of prediction. Moderate to high heritabilities were observed for average daily gain (0.64) and carcass traits including hip height (0.67), slaughter weight (0.47), shrink (0.26), fat thickness (0.63), carcass weight (0.55), dressing percentage (0.77), loin muscle area (0.44), kidney, pelvic, and heart fat (0.46), yield grade (0.71), marbling score (0.44), and USDA quality grade (0.47). Low heritabilities were observed for tenderness traits including Warner-Bratzler shear force on days 7 (0.14), 14 (0.14), and 21 (0.06), taste panel tenderness (0.11), and calpastatin activity (0.07). Predicted breeding values for Warner-Bratzler shear force (day 14) ranged from -1.77 for sire 3 to 0.96 for sire 6. This indicated that one would expect the average shear force of a large number of progeny from sire 3 to be 1.4 lb lower in shear force (more tender) than a large number of progeny from sire 6. Likewise, ranges in predicted breeding values for marbling score and USDA quality grade indicated that a large number of calves from sire 13 would be expected to have an average marbling score 62.2 units higher and an average USDA quality grade 46.7 units higher than the averages of a large number of progeny from sire 10. Thus, this information provides additional tools for breeders to use at their discretion in the selection for carcass and production traits in Brahman cattle.