Efficiency of growth and wool production of young Merino ewes from a flock selected for fertility

Abstract

A handfeeding experiment was conducted with weaner ewe lambs from two Merino flocks. One flock had been selected for high net reproductive rate, growth rate and wool production (fertility flock) ; the other flock was a randomly selected control flock (random flock). Single and twin born lambs from each flock were used in the experiment. Lambs were randomized into four treatment groups and offered the diet either ad libitum or at one of three levels estimated to restrict growth rate to 50, 100 and 150 g day-1. At each level of feeding, fertility flock lambs grew faster and were more efficient in converting feed to liveweight gain. Over the whole experiment the feed conversion efficiencies in g gain per kg digestible organic matter intake per day were 218 and 185 (P < 0.05) for the fertility and random flocks respectively. There were no significant differences in growth rate or efficiency of conversion of feed to liveweight gain between single-born and twin-born lambs. Random flock lambs had a significantly higher wool growth rate and were more efficient converters of feed to wool than fertility flock lambs. Gross efficiencies were 10.8 and 9.1 g clean wool per kg digestible organic matter intake per day (P < 0.05) for random and fertility flock lambs respectively. Single-born lambs grew significantly more wool than twin-born lambs but there was no significant difference between birth types in the efficiency of conversion of feed to wool.