|West, R. - UNIVERSITY OF FLORIDA|
|Johnson, D. - UNIVERSITY OF FLORIDA|
|Olson, T. - UNIVERSITY OF FLORIDA|
Submitted to: Brahman Journal
Publication Type: Trade Journal
Publication Acceptance Date: December 14, 2002
Publication Date: February 14, 2003
Citation: Riley, D.G., Chase, C.C., West, R.L., Johnson, D.D., Olson, T.A., Hammond, A.C., Coleman, S.W. 2003. Estimation of the genetic control of brahman beef quality, quantity, and palatability traits. Brahman Journal.33(12):27. Interpretive Summary: Brahman crossbreds are an important part of cow-calf production in the Gulf Coast region of the United States, primarily because of their adaptability to hot, humid climates, high pest loads, and low quality forage. However, relatively large numbers of straightbred Brahman cattle are required to generate crossbred cows for various types of crossbreeding production systems. The production difficulties associated with straightbred Brahman cattle include inferior carcass yield and quality grade and tenderness as compared with Bos taurus beef cattle. Knowledge of the degree of genetic control over these types of traits is necessary in order to design selection programs and assess their potential effectiveness. We estimated heritabilities of these carcass traits in Brahman steers and heifers: average daily gain in the feed yard, hip height at slaughter, slaughter weight, hot carcass weight, adjusted 12th rib fat thickness, loin muscle area, percentage kidney, pelvic, and heart fat, USDA yield and quality grade, dressing percentage, marbling score, cutability, retail yield, carcass hump height. The percentage of the variation due to genetics in these traits was approximately the same (30 to 60%) as has been reported for other breeds of cattle. Heritabilities were estimated for these traits related to tenderness: Warner-Bratzler shear force, sensory tenderness, juiciness, connective amount, flavor, and calpastatin activity. The percentage of the variation due to genetics in these traits was slightly lower (less than 20%) than other research has reported. Brahman cattle have been frequently criticized for low marbling (and hence quality grade) and tenderness. These results indicate that sires can be identified that are above average in marbling and could be used to improve this trait relatively quickly in Brahman cattle, without antagonistic effects on other carcass traits. Results also suggest that tenderness improvement in the breed should include non-genetic methods, such as post-slaughter methods.
Technical Abstract: Heritabilities, genetic and phenotypic correlations were estimated from feedlot, carcass, and palatability data collected from Brahman calves (n = 504) in central Florida from 1996 to 2000. Data were analyzed using animal models in MTDFREML (Boldman et al., 1995). Models included contemporary group (n = 44; groups of calves of the same sex, fed in the same pen, slaughtered on the same day) as a fixed effect and calf age in days at slaughter as a continuous variable. Estimated feedlot trait heritabilities were 0.64, 0.67, 0.47, and 0.26 for ADG, hip height at slaughter, slaughter weight, and shrink. The USDA yield grade estimated heritability was 0.71; heritabilities for component traits of yield grade, including hot carcass weight, adjusted 12th rib backfat thickness, loin muscle area, and percentage kidney, pelvic, and heart fat were 0.55, 0.63, 0.44, and 0.46, respectively. Heritability estimates for dressing percentage, marbling score, USDA quality grade, cutability, retail yield, and carcass hump height were 0.77, 0.44, 0.47, 0.71, 0.5, and 0.54, respectively. Estimated genetic correlations of adjusted 12th rib backfat thickness with ADG, slaughter weight, marbling score, percentage kidney, pelvic, and heart fat, and yield grade (0.49, 0.46, 0.56, 0.63, and 0.93, respectively) were generally larger than most literature estimates. Estimates of heritability for shear force, tenderness score, connective tissue amount, juiciness, flavor, and calpastatin activity were 0.14, 0.11, 0.12, 0.05, 0.04, and 0.07. Results indicate that sufficient genetic variation exists within the Brahman breed for design and implementation of effective selection programs for important carcass quality and yield traits. Results suggest that selection for tenderness improvement should be complemented by post-slaughter intervention procedures.