Factors affecting productivity of sheep flocks in Ontario

Ontario Sheep Flock Improvement Program records from 1985 to 1989 on 216 670 lambs in 4894 flocks were used for this study. Flocks were required to have progeny from at least five ewes and the lams were grouped by breed type, ram breed, ewe size and birth year, all within producer. Death loss, percent of lambs fostered and effects associated with ewe age and size accounted for a significant portion of the variation in flock productivity. The ranking of breeding system and ram breed effects varied among mating programs. Flock productivity increased with increasing number of lambs born per ewe and ewe size. Flocks with ewes that averaged 59 mo of age had the highest productivity. Flock productivity increased 60 kg flock −1 (2.6 kg ewe −1 ) from 1985 to 1989. Key words: Sheep, flock productivity