FAT GROWTH AND PARTITIONING AMONG THE DEPOTS IN DOUBLE MUSCLED AND NORMAL CATTLE

Abstract

Eighteen Double Muscled (DM), 18 Beef Synthetic (SY) and 18 Hereford (HE) bulls were serially slaughtered from approximately 250 to 800 kg liveweight to determine the influence of maturity type and "double muscling" on fat growth, partitioning and distribution. The fatty tissue was dissected into subcutaneous fat (SCF), intermuscular fat (IMF) and carcass cavity fat (CCF); the sum of these depots was used as total side fat (TSF). Relative to TSF, DM did not differ significantly from the other maturity types in growth rates of SCF, IMF and CCF, but relative to fat percent in the side, DM tended to have much lower growth rates for SCF and CCF. The common growth coefficients indicated that as TSF increased the proportion of SCF increased (b > 1; P < 0.05), the proportion of IMF decreased (b < 1; P < 0.05), and the proportion of CCF remained relatively constant (b = 1; P > 0.05). At equal TSF, as expected, HE tended to partition more of their fat to the subcutaneous depot, whereas DM and SY tended to partition more of their fat to the intermuscular and carcass cavity fat depots. Relative to HE, DM followed late-developing fat partitioning patterns. The hypodevelopment of fat depots in the carcasses of the muscular hypertrophied animals followed an inner-outer gradient which was most pronounced in the subcutaneous fat depot. Key words: Cattle, fat growth, double muscling, breed type