Published online by Cambridge University Press: 02 September 2010
Masham ewes were mated at three stages of the breeding season, early (15 September to 20 October), mid (20 October to 24 November) and late (15 December to 19 January), at two different body condition scores, 4 and 2, for 3 successive years. The mean scores achieved for body condition 4 were 3·6, 3·7 and 3·9 for early, mid and late respectively and for body condition 2 were 2·4, 2·3 and 2·2. In the late lambing flock more ewes were marked by vasectomized rams and less ewes were barren than in the early and mid flocks. The ewes in higher body condition at mating had significantly more triplets and fewer singles, and a higher lambing percentage (183 versus 165). This effect of body condition on litter size distribution was significant at each time of mating, with the ewes at the late mating producing significantly fewer triplets and more singles; this difference was caused by a reduction in the performance of the body condition 4 ewes in the late group.
Young ewes in the body condition 4 group produced significantly fewer triplets and more singles than the mature ewes in the same body condition group, but at the lower body condition age had no effect on litter size distribution.