Growth of bovine tissues 4. Genetic influences on patterns of bone growth and distribution in young bulls

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Abstract
Bone growth patterns and distribution were compared in joints of carcasses from 277 young bulls, progeny of eight sire breeds and two dam breeds, serially slaughtered at 300 kg live weight, 12 and 15 months of age. The growth pattern for bone in a joint was estimated from the allometric equation (Y = aXb). Growth coefficients (b) were homogeneous among breed groups for bone in each joint relative to total side bone indicating that the different breeds followed similar patterns of differential bone growth. Growth impetus of limb bones was lowest in the distal parts, increasing to the proximal regions, with the fore limb showing higher growth impetus than the hind limb. Bones of the whole thoracic region showed a high growth impetus and those of the lumbar region the highest. The cervical vertebrae showed only average growth impetus, maintaining a constant proportion of total bone. Significant sire breed differences were found in the proportion of bone in each joint when adjusted to equal side bone weight but the differences were rather small and probably commercially unimportant. Differences among sire breed groups reflected differences in maturity type, with progeny of Here-ford sires representing early maturity and progeny of Chianina sires the other extreme. Functional association between muscle and bone was not reflected in a similarity of growth patterns, except for the muscles and bones of the limbs.