EFFECTS OF AUTUMN SHEARING OF SPRING-BORN EWE LAMBS ON LIVEWEIGHT ANDREPRODUCTIVE-PERFORMANCE

Ewe lambs have a lower incidence of mating and a lower conception rate than adult ewes. There is evidence that these reproductive characteri stics can be improved by shearing prejoining. The effects of shearing spring-born ewe lambs in autumn on subsequent liveweight and reproduct ive performance were evaluated in an experiment repeated over 3 years. Half of the flock was shorn in mid-September and half remained unshor n. All were managed together as a single group thereafter. Fertile har nessed rams were joined on 16 October each year and removed in early D ecember. Matings were recorded daily and ovulation rate was determined by laparoscopy within 10 days of first mating. Shearing had no signif icant effect on liveweight but liveweight gain between shearing and jo ining was lower for the shorn animals (P<0.05). The proportion mated ( shorn 93%, unshorn 96%) and overall conception rate (shorn 73%, unshor n 76%) were unaffected by treatment. While there was no overall effect of shearing on conception rate to first service (P>0.3) there was a y ear x shearing interaction (P<0.05). In the first year, shorn ewes had a higher conception rate but the opposite effect was observed in the second year. Shearing had no significant effect on the date of first s ervice, on ovulation rate or on embryo survival in those ewes which co nceived to first service. The reproductive performance of ewe lambs wh ich lambed, in terms of ovulation rate, number of services to concepti on, conception date, lambing date, litter size and gestation length, w as unaffected by shearing. Shorn ewes tended to give birth to heavier lambs but the difference (0.2 kg) did not reach significance (P=0.2). In this study, shearing prior to joining did not enhance the reproduct ive performance of ewe lambs.