The relationship of various muscular and skeletal scores and ultrasound measurements in the live animal,and carcass classification scores with carcass composition and value of bulls

The relationships of live animal muscular and skeletal scores and ultrasound measurements and carcass conformation and fat scores with carcass composition and value were determined using 74 bulls. The animals consisted of 53 late-maturing breed crosses and 21 Holstein–Friesian slaughtered at 13 to 17 months of age. They were offered concentrates ad-libitum and 1 kg of grass silage dry matter per head daily for the final 139 day finishing period. Live animal muscular and skeletal scores and ultrasonic muscle and fat depth measurements of the M. longissimus dorsi were recorded at 8 to 12 months of age and pre-slaughter. Following slaughter, carcasses were classified for conformation and fatness and the right side of each carcass was dissected into meat, fat and bone. Carcass conformation and fat scores, (scale 1 to 15) ranged from 4.7 to 14.4 and 2.7 to 11.5, respectively. Pre-slaughter muscular scores showed significant positive correlations with kill-out proportion (r = 0.82), carcass meat proportion (r = 0.72), conformation score (r = 0.94), carcass value (r = 0.72), and the proportion of high-value meat cuts in the carcass (r = 0.49), and significant negative correlations with carcass bone (r = − 0.89) and fat (r = − 0.32) proportions. The associations between pre-slaughter muscular scores and proportion of high-value cuts in meat, perinephric plus retroperitoneal fat and fat score were not significant. Corresponding correlations with muscular scores at 8 to 12 months of age were generally lower than those recorded pre-slaughter. Correlations of ultrasound muscle depth with carcass traits showed similar trends but lower values to those obtained using the muscular scoring procedure. Ultrasound fat depth pre-slaughter was positively correlated with carcass fat proportion (r = 0.56) and fat score (r = 0.54), and negatively correlated with carcass meat proportion, proportion of high-value cuts and carcass value. Correlations with other carcass traits were not significant. Correlations of live animal skeletal scores with carcass traits were generally non-significant. A one unit (scale 1–15) increase in carcass conformation score was associated with significant increases in kill-out proportion, meat yield and carcass value of 11.9 g/kg, 11.9 g/kg and 5.8 cent/kg, respectively. Corresponding effects for a one unit change in fat score were − 2.9 g/kg, − 11.1 g/kg and − 4.9 c/kg. In conclusion, live animal muscular scores and ultrasound measurements and carcass conformation and fat scores were shown to be useful predictors of carcass composition and value.