Effect of weaning pre- or post-mating on performance of spring-mated ewes and their lambs in New Zealand

Abstract

The objective of this experiment was to determine the effect of lactation over the breeding period and early gestation on ewe reproductive performance and liveweight. Romney ewes (n = 206) with lambs at foot were allocated to either Early or Late weaning groups, synchronised with CIDRs and joined with Suffolk rams 69 days postpartum (P0). Lambs from the Early group were weaned at P0 while lambs from the Late group were weaned at P21. The ovaries of each ewe were observed laparascopically at P9. Late weaned lambs were significantly heavier (P < 0.001) at P21 and P47 than lambs in the Early group. There was no effect of ewe treatment on ewe reproductive performance, liveweight over the breeding period, number of corpora lutea present, pregnancy rates, or on liveweight of the ewes at the subsequent lambing and lactation. Birth and liveweights of subsequent lambs were not affected by the treatment of the ewe over the breeding period. This research suggests that the breeding of suckling ewes in an accelerated lamb production system has no effect on ewe reproductive performance or on subsequent lamb production. © 2006 Taylor & Francis Group, LLC.