Carcass Characteristics of Yearling Normal and Double Muscle Cross Bulls

Data on 99 young bulls, which were the progeny of matings of either double muscle bulls and normal cows (DMx) or normal bulls and normal cows (N) born over three calving seasons, were analyzed to compare the carcass characteristics and lean yield of yearling DMx and N bulls. DMx carcasses had larger (P < 0.001) ribeye areas and cutability but smaller (P < 0.001) grade fat and average fat thicknesses than N carcasses, when the data were adjusted to either constant slaughter age (395.7 d) or constant carcass weight (304.7 kg). Muscle:fat and muscle:bone ratios and percent muscle in the 10th-1lth-12th rib joint were higher (P < 0.001), while percent fat and percent bone in the rib joint were lower (P < 0.005) in DMx compared to N carcasses, when the data were adjusted to either constant grade fat thickness (10.0 mm) or constant rib joint weight (4871.4 g). The magnitude of the observed superiority of DMx over normal carcasses in lean yield was not the same across carcass grades. For A1 or A2 carcasses, rib joints from DMx carcasses had 8.8 and 5.7%, respectively, more (P < 0.05) muscle than those from N carcasses.