GROWTH OF BOVINE TISSUES .2. GENETIC INFLUENCES ON MUSCLE GROWTH AND DISTRIBUTION IN YOUNG BULLS

Muscle weight distribution was compared by jointing and complete tissue separation of carcasses from 277 young male progeny of eight sire breeds and two dam breeds, serially slaughtered at 300 kg live weight, 12 months and 15 months of age. The sire breeds were Simmental, Charolais, Danish Red and White, Romagnola, Chianina. Hereford, Blonde d'Aquitaine and Limousin; the dam breeds were Danish Red and Danish Black Pied. Growth impetus for muscle in each joint was established from the allometric equation (Y = aXb). Growth coefficients, b, were homogenous among breeds, indicating similar muscle development patterns over the range of weights studied. Growth impetus waves increased centripetally on the limbs, caudocephalically on the whole of the body (being more marked dorsally) and dorsoventrally on the trunk. There were small but significant breed differences in the proportion of muscle in different joints at similar total muscle weight. They probably reflect differences in maturity and other minor functional influences. Chianina and Hereford crosses were the two extremes for muscle distribution with many of the remaining breed groups being very similar. Differences were already established by 300 kg live weight and muscle growth patterns were similar among breeds over the range of the experiment. © 1978, British Society of Animal Science. All rights reserved.