The influence of previous reproduction on subsequent fertility in multiparous ewes

Abstract

Adult ewes often lose live weight while lactating, but should regain it prior to the following mating if pasture availability or sheep numbers are managed judiciously. Data from a self-replacing flock of Wiltshire ewes four to nine years of age (n=267) was available for 622 lambing events across a 13-year period. Wiltshires grow little wool and live weight was not complicated by fleece weight. The average number of lambs born was 1.76 per ewe per year during the course of the study. Ewes not rearing a lamb (13.2%), or rearing singles (42.4%), twins (42.4%), or triplets (1.9%), were present at weaning. All ewes were grazed together and when their lambs were weaned, those that did not raise a lamb (67.4 ± 9.7 kg) were heavier than ewes that raised singles (63.0± 9.3 kg), twins (59.9 ± 8.5 kg) or triplets (59.7 ± 7.7 kg) (P<0.001). Despite this, the previous number of lambs weaned did not influence the number of lambs born in the subsequent year (P = 0.43), but was positively associated with ewe liveweight gain between weaning and mating (P<0.01). Number of lambs born was positively influenced by ewe live weight at mating up to 65kg. Reproductive performance was not influenced by the previous year, providing ewes were able to increase live weight between weaning and mating.