Genetic correlations for litter weight weaned with growth, prolificacy, and wool traits in Columbia, Polypay, Rambouillet, and Targhee sheep

Total litter weight weaned at 120 d postpartum per ewe lambing is often bel ieved to be a measure of range ewe productivity. Genetic correlations for l itter weight weaned at 120 d with prolificacy, growth, and wool traits for Columbia, Polypay, Rambouillet, and Targhee sheep were estimated using REML with animal models. Observations per breed ranged from 5,140 to 7,083 for litter weight weaned, from 5,140 to 7,095 for prolificacy traits, from 7,75 0 to 9,530 for growth traits, and from 4,603 to 18,443 for wool traits. Her itability estimates for litter weight weaned were low and ranged from 0.02 to 0.11. Fraction of variance due to permanent environmental effects averag ed 0.05 and, due to effects of mates, averaged 0.01. Estimates of genetic c orrelations with litter weight weaned varied from breed to breed. The range s were as follows: 0.42 to 0.65 with litter size born, 0.80 to 0.99 with li tter size weaned, -0.22 to 0.28 with birth weight, -0.07 to 0.23 with avera ge daily gain to weaning, -0.56 to 0.19 with fleece weight, -0.15 to 0.02 w ith fleece grade, and -0.11 to 0.08 with staple length. Results suggest tha t, if selection were practiced on litter weight weaned, the average correla ted responses would be expected to be favorable or neutral for prolificacy, growth, and wool traits although responses might vary from breed to breed.