Growth of bovine tissues 3. Genetic influences on patterns of fat growth and distribution in young bulls

Abstract

ABSTRACTFat growth and distribution were studied by jointing and complete tissue separation of carcasses from 277 young bull progeny of eight sire breeds and two dam breeds, serially slaughtered at 300 kg live weight, 12 and 15 months of age. Growth impetus for fat in each joint was established from the allometric equation (Y = aXb). Differential growth of fat in different joints resulted in marked differences in percentage of fat in various joints as fattening progressed. Growth coefficients,b, for fat in each joint were homogeneous among breed groups, indicating similar fat development patterns over the weight range studied. Growth impetus for fat was lowest in the distal limbs and in the proximal hind limb. Fat growth in the proximal fore limb was proportional to total fat. Along the dorsal line, low impetus was found in neck and rump regions, increasing to a high impetus in the mid-back region. Ventrally the fat of the flank showed the highest growth impetus of all regions with fat in the brisket and flat ribs also showing an increasing proportion with increases in total fat.Small but significant differences among sire breeds were found for the amount of fat in each joint at a standard amount of total fat in the carcass. Differences found among sire breeds in fat distribution were not associated with differences in maturity type.