Effect of phenotypic expression of Brahman breeding on marbling and tenderness traits.

Steers with known proportions of Brahman and Hereford breeding (80 quarter-bloods, 25% Brahman x 75% Hereford and 79 half-bloods, 50% Brahman x 50% Hereford) were used to determine the effect of phenotype on marbling and beef tenderness characteristics. Three experienced evaluators independently classified each live steer according to estimated proportion of Brahman breeding based on phenotypic evidence of Brahman breed characteristics. The steers were slaughtered, their carcasses were graded, and a carcass. Samples of longissimus muscle were obtained for measurement of 24-h calpastatin activity, sensory panel evaluation, and Warner-Bratzler shear (WBS) force measurements. Paired steaks were aged (6 and 18 d postmortem) and palatability determinations were completed. Estimates of live animal phenotype ranged from 0/16 to 9/16 for quarter-blood Brahman steers and from 1/14 to 13/16 for half-blood Brahman steers. Neither live animal phenotype nor carcass hump height was correlated with marbling score. Live animal phenotype was correlated (P < .01) with taste panel tenderness ratings (rd6 = -.36; rd18 = .36) and shear force values (rd6 = .36; rd18 = .30). Moreover, carcass hump height exhibited low, negative correlations (P < .05) with panel tenderness scores (rd6 = -.16; rd18 = -.28) and low, positive correlations (P < .10) with shear force (rd6 = .13; rd18 = .16). Steaks from steers classified as more than 3/8 Brahman were tougher (P < .05) than steaks from steers classified as 3/8 or less Brahman. Steaks from carcasses with hump height measurements of 7.60 cm or greater had lower panel tenderness ratings and higher WBS values (P < .05) than steaks from carcasses with hump heights less than 6.35 cm. Quarter-blood and half-blood Brahman steers that were similar in phenotype produced steaks that were similar in tenderness. Results of this study suggest that as phenotypic evidence of Brahman breeding increases the tenderness of cooked steaks from Brahman crossbred steers decreases.