GENERAL, SPECIFIC, MATERNAL AND RECIPROCAL EFFECTS FOR EWE PRODUCTIVITY IN CROSSING FIVE BREEDS OF SHEEP

Five breeds of sheep (Minnesota 100, 102, 103 and 105, and Shropshire), and their two breed crosses, including reciprocals, were raised at the University of Minnesota's Agricultural Experiment Stations, Rosemount and Waseca. Included in this study were 421 purebred and 1037 crossbred ewes and their 367 purebred and 849 Suffolk-sired crossbred lambs born over a 5-yr period. Estimates of heterosis, pure breed, general, specific, maternal and reciprocal effects were obtained for fertility, prolificacy, livability, overall reproduction, and total and average lamb weights per ewe at birth and weaning (100 days). Significant differences were observed for prolificacy, livability, and total and average lamb weights per ewe at birth and weaning. General combining ability was important (P < 0.01) for prolificacy and average lamb weight per ewe at birth and weaning. Specific combining ability was significant for prolificacy, total lamb weight per ewe at birth, and average lamb weight per ewe at weaning. Maternal and reciprocal effects were not important (P > 0.05). Significant interactions of location with specific combining ability and maternal ability were observed for average lamb weight per ewe at weaning. Breeds ranked differently on purebred performance and general combining ability. Heterosis, pure breeds, and general and specific combining ability had important effects. Therefore, both additive and non-additive effects should be considered in developing breeding strategies to maximize productivity for commercial lamb production. Key words: Sheep, breed, ewe productivity, genetic effects