Bovine Compositional Interrelationships

Abstract

Composition studies were completed using 49 steers representing variations in muscularity that included double muscled cattle. Results indicated that non-muscular cattle were fatter than anticipated when evaluated subjectively, and the reverse was true for muscular cattle. Muscular cattle contained from 2 to 7% more fat-free muscle and this was attributed to higher muscle-bone ratios; however, fatness was the dominating variable in determining ultimate composition. The proportionate contributions of each muscle to total muscle mass and each bone to total skeletal mass was nearly constant for all cattle, and this was also true for body parts (holding fat content and weight constant). Wizen fat content and live empty body weight were held constant, all cattle converted equal quantities of feed to fat-free muscle. The combination of fat depth, longissimus area and marbling content provided a useful combination of variables to predict quantity of fat-free muscle. Muscular cattle had higher dressing yields which were attributed to their possessing proportionately smaller body cavities. Fatter cattle did not have higher dressing yields when live weight and muscularity were held constant because it appeared that increased quantities of mesentery fat compensated on a proportional basis for increased quantities of carcass fat. One double muscled steer possessed the biological capacity to deposit excess quantities of fat when time on feed was unlimited.