Genetic Markers, Cattle Disposition, and Stress Relative to Variations in Beef Tenderness

The objective of this research was to evaluate the efficacy of genetic markers, disposition, and animal stress on variations in beef tenderness. Warner-Bratzler shear force (WBSF) values on 570 mixed breed heifers and steers were used to determine estimates of genetic selection. Cattle used for this analysis were marketed from 2008 to 2011, and included five different feedlot based research projects at the Carrington Research Extension Center (Carrington, ND). Tissue samples were collected for IGENITY? (Merial Limited, Duluth, GA) analysis. Results included both selection indices and molecular breeding values for hot carcass weight, ribeye area, yield grade, fat thickness, percent choice, marbling, tenderness, docility, heifer pregnancy rate, maternal calving ease, and stayability. These genetic based parameters were compared with actual carcass values and measurements of temperament including exit velocity, chute score, and capture score. Genetic marker assisted selection may offer a more effective means of improving cattle management strategies and product quality; however there is progress to be made on the accuracy of such predictions. In the second project, the effect of temperament and slaughter method on Minolta color scores and tenderness was evaluated. Measurements of temperament were obtained prior to slaughter on Angus x Peidmontese crossbred heifers. Heifers were slaughtered on two consecutive Mondays using either Kosher or captive-bolt slaughter methods. At approximately 24 h post-mortem, carcass measurements and marbling scores were obtained. Longissimus thoracis (LT) samples were collected and aged 14 d prior to Minolta color score and WBSF measurements. Chute score, capture score, and vocalization scores significantly correlated (P < 0.03) with blood lactate concentration. The LT from Kosher slaughtered heifers had significantly higher (P < 0.01) L*, a*, b* and WBSF values than that of captive bolt stunned heifers. The LT from captive bolt stunned heifers had significantly higher (P = 0.04) marbling, and a tendency (P = 0.08) for increased cook loss compared with that from Kosher slaughtered heifers. These data indicate that chute behavior is significantly correlated to measurements of blood lactate and suggests that the Kosher slaughter method may negatively affect meat quality parameters compared with the captive-bolt stunning method