ACCUMULATION OF LIPID IN RIB CUTS FROM BULL AND HEIFER CARCASSES OF TWO BREEDS

Abstract

A trial is reported comparing the accumulation of lipid in rib cuts from 12 bull and 12 heifer carcasses from two breed types: Hereford (HE) and Dairy Synthetic (DY). Serial slaughter was carried out from weaning (163 ± 15.1 (SD) days) to approximately 16 mo of age. The left side of each carcass was broken in two quarters, and then eight wholesale cuts. Fat samples (subcutaneous, intermuscular, body cavity) and a muscle sample were taken from the rib cut and analyzed for their lipid and energy contents. The rate of accumulation of lipid was estimated from the growth coefficient, b, in the allometric equation (Y = aXb) using total separable fat as the independent variable. Growth coefficients were homogeneous both between breeds and sexes indicating that neither sex nor breed influenced the relative accumulation of lipid. A significant sex difference (P < 0.01) was found when the lipid content of the fat depots and the rib muscle were adjusted to a constant side separable fat. No breed differences (P > 0.05) were found in the lipid content of the fat depots. A significant difference between sexes was also found in the energy content of the fat depots, but no differences were found between breeds, when the data were adjusted to the mean of the total side fat.