376 Genetic Approaches to Improve Reproductive Performance in the U.S. Sheep Industry

Abstract The U.S. sheep industry has experienced many changes over the last 50 years, most prominent being a 75% reduction in national breeding ewe inventory. Wool now accounts for ~10% of enterprise returns compared to ~80% from sale market lambs. Most objective work indicates greatest emphasis should be placed on traits associated with reproductive efficiency [e.g., number lambs born/weaned (NLB/NLW), lamb survival]. Still, average NLB across (1.07 lambs/ewe) and within geographic regions (East = 1.13, Midwest 1.25, West 1.09, Southwest 0.79 remains low. Several genetic technologies are available improve performance. Introgression large effect gene variants, such as those BMPR-1B, have increased by ~1.0 ~1.5 heterozygous homozygous ewes, respectively. However, without joint improvement maternal ability and/or husbandry, advantages NLW less pronounced few producers utilize variants practice. Reproductive present challenges selection programs they lowly heritable (< 0.15) sex-limited. Previous single-trait experiments had modest (0.01 – 0.02 lambs/yr). Selection accuracy is greatly improved including pedigree genomic relationships when deriving estimated values (EBV). Since 2000, EBV 0.01 lambs/yr concurrent direct (0.02 kg/yr) (0.04 weaning weight Polypay flocks enrolled National Sheep Improvement Program (NSIP). NSIP represent < 1% production-oriented so considerable expansion needed realize within-breed at level. Perhaps importantly, differences exist breeds utilized greater extent strategic crossbreeding systems. Optimizing performance specific production environments essential sustainability industry.