U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska


Document Type


Date of this Version



Published in Sheep & Goat Research Journal, Volume 20, 2005.


Ewe production traits and ability to breed out of season were compared for the Dorper (DO), Katahdin (KA), and St. Croix (SC) breeds between 2000 and 2005. Sheep were managed on grass pasture and were supplemented with corn/soybean meal and free-choice, trace-mineral mix. Ewes were exposed to rams of their respective breeds in late summer (August/September), winter (December), or spring (April/ May) for 30-day breeding periods. Lambs were weighed at birth and 60 days of age. Pregnancy and lambing rates and litter birth weight were greater for all breeds bred in winter and lowest in spring. Pregnancy losses were greater and birth weights reduced for DO and KA ewes less than two years of age bred in the spring compared with other seasons. Birth weights of lambs were not affected by season, but weaning weights were greatest for all breeds when ewes were bred in summer. Relative efficiency at weaning (kg of lamb produced/kg ewe weight) was greatest for summer-bred ewes and greatest for KA compared with DO and SC ewes. In summary, DO, KA, and SC ewes are capable of out-of-season breeding in Arkansas. However, relative efficiency and weaning weights were lowest for spring-bred ewes and fertility of yearling ewes of all breeds was reduced during spring breeding.