THE ACCUMULATION AND DISTRIBUTION OF FAT IN EWE AND RAM LAMBS

Abstract

Sixteen ewes and 22 rams (crossbred lambs) were grouped by sex and fed a diet based on grain and hay. All animals were slaughtered over a 4-wk period to give a range of slaughter weights (24.0–61.8 kg). After slaughter, one side of each carcass was broken into the four primal wholesale cuts (leg, loin, rib, shoulder) with the rest of the carcass discarded as trim. The four wholesale cuts were separated into fat (subcutaneous fat (SF), intermuscular fat (IF), kidney fat (KF) and body cavity fat (BCF)) muscle and bone. Depot fat accretion in the carcass was investigated using the allometric equation with side weight and side fat weight as the independent variables. Total rate of fat deposition relative to side weight was higher in ewes than rams, and ewes had more total fat than rams when comparisons were made at the same side weight (10.03 kg). However, growth coefficients for depot fat accumulation in a side and in the wholesale cuts relative to side fat were homogeneous between sexes indicating that sex did not affect the relative accumulation of fat. SF, however, had the highest growth coefficient (1.23) and IF the lowest (0.74). At equal total side fat ewes had significantly more IF in a side than rams, but overall the differences in the distribution of fat in the wholesale cuts were minor and commercially unimportant. It was concluded that the ewes had a faster rate of fat deposition than rams but both sexes followed the same pattern of differential fat accumulation, and that the distribution of fat was dependent mainly on the total amount of fat in a carcass. Key words: Fat, lambs, carcass