Comparative performance of South Australian Merino and Poll Dorset × Merino ewes mated to Suffolk rams

Abstract

Reproductive performance of Poll Dorset × South Australian Merino (PD × M) ewes was superior to that of South Australian Merino (M) genotype with 10% more pregnant ewes, 11% more lambs born per pregnant ewe, and a 7% better lamb survival rate. This resulted in 22 more lambs slaughtered per 100 ewes exposed. Merino ewes produced more greasy wool (6.08 vs. 4.35 kg) of finer fibre diameter (27.5 vs. 32.9 μm) than PD × M ewes. Mature liveweight at mating of PD × M ewes was 17% more than that of M ewes (57.8 vs. 50.1 kg). Carcasses of lambs from PD × M ewes were heavier (18.7 vs. 16.8 kg), shorter per unit carcass weight (698 vs. 783 mm carcass length per 16.9 kg carcass weight), and fatter (13.0 vs. 11.6 mm; GR fat depth) when evaluated at similar carcass weight as compared with carcasses of lambs from M ewes. Skin weight and skin wool characteristics of lambs were similar between genetic groups. Under 1987 and 1988 Australian wool and sheep meat market price conditions, the economic worth of M ewes per unit metabolic weight (mature weight 0.75) was 45% more profitable than that of PD × M ewes.