Genetic parameters for growth and carcass traits of Brahman steers

¹ University of Louisiana at Monroe
² LSU Agricultural Center, Baton Rouge
³ Texas A&M Research and Extension Center, Corpus Christi
⁴ Woodland Mills, TN

^* To whom correspondence should be addressed. E-mail: smith{at}ulm.edu.

	Abstract

Spring born purebred Brahman bull calves (n = 467) with known pedigrees and sired by 68 bulls in 17 private herds in Louisiana were purchased at weaning from 1996 through 2000 to study variation in growth, carcass, and tenderness traits. After purchase, calves were processed for stocker grazing on ryegrass, fed in a south Texas feedlot, and processed in a commercial facility. Carcass data were recorded 24 hr postmortem. Muscle samples and primal ribs were taken to measure calpastatin activity and shear force. An animal model was used to estimate heritability, genetic correlations, and sire EPD. Relatively high heritability estimates were found for BW at slaughter (0.59 ± 0.16), hot carcass weight (0.57 ± 0.15), longissimus muscle area (0.50 ± 0.16), yield grade (0.46 ± 0.17), calpastatin enzyme activity (0.45 ± 0.17), and carcass quality grade (0.42 ± 0.16); moderate heritability estimates were found for hump height (0.38 ± 0.16), marbling score (0.37 ± 0.16), fat thickness (0.36 ± 0.17), feedlot ADG (0.33 ± 0.14), 7-d shear force (0.29 ± 0.14); and 14-d shear force (0.20 ± 0.11); relatively low heritability estimates were found for skeletal maturity (0.10 ± 0.10), lean maturity (0.00 ± 0.07) and percent kidney, pelvic, and heart fat (0.00 ± 0.07). Most genetic correlations were between -0.50 and +0.50. Other genetic correlations were 0.74 ± 0.27 between calpastatin activity and 7-d shear force, 0.72 ± 0.25 between calpastatin activity and 14-d shear force, -0.90 ± 0.30 between yield grade and 7-d shear force, and -0.82 ± 0.27 between fat thickness and 7-d shear force. Heritability estimates and genetic correlations for most traits were similar to estimates reported in the literature. Sire EPD ranges for carcass traits approached those reported for sires in other breeds. The magnitude of heritability estimates suggests that improvement in carcass yield, carcass quality, and consumer acceptance traits can be made within the Brahman population.

Key Words: Brahman steers, carcass traits, genetic parameters

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