Influence of maternal liveweight on reproductive performance and wool production of heterozygous Booroola Merino × Coopworth (FecBFec+) and Merino × Coopworth ewes

The concurrent and long-term effects of feeding high (H) and low (L) levels of nutrition from weaning to 4 years of age were measured in 188 high fecundity heterozygous Booroola Merino × Coopworth (BC) ewes (FecB Fec+) and 58 low fecundity New Zealand Merino × Coopworth (MC) ewes. Following the cessation of differential feeding, all groups were grazed on a common plane of nutrition for 2 years. There were no significant nutrition by genotype interactions for liveweight, lamb performance, or ewe lambing performance. During common feeding, carryover effects of restricted feeding were apparent only for liveweight and barrenness. The mature liveweight of H ewes was 60–70 kg throughout differential feeding, which was 12–15 kg heavier than L ewes. L ewes showed 58% compensatory growth but were still 5.1 kg lighter than H ewes (P < 0.05) at the end of the experiment. Ovulation rates of L ewes were 0.07–0.51 lower than their H contemporaries during differential feeding and this was significant (P < 0.05 ...