Liveweight-productivity relationships in sheep

Abstract

The relationships between liveweight at mating, lamb drop, lamb growth rate, and f1eece weight in Corriedale ewes have been studied by the analysis of data derived from 36 different mobs of ewes extending over several years and comprising 3,910 sheep. Lamb drop or twinning is significantly and positively correlated with liveweight, values being +0.63 between mobs and +0.15 within mobs. Regression of percentage twins on liveweight gives values equivalent to increases of 8.2 per cent between mobs and 4.6 per cent within mobs for a 10 per cent increase in liveweight from 100 lb to 110 lb. Lamb weaning weight is correlated with ewe liveweight to the extent of +0.08 (within mobs) and increases by only 1.8 per cent per 10 percent increase in liveweight. The correlation of f1eece weight with liveweight is +0.24, and f1eece weight increases by 4.3 per cent (within mobs) for each 10 per cent increase in liveweight. The increases in lamb and wool production with increasing liveweight are of approximately t...