Project Number: 2056-31610-006-15-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2018
End Date: Sep 30, 2019
1) Investigate breed differences in meat- and wool-type breeds for economically relevant traits. 2) Determine how relevant traits from different breeds combine in crossbred progeny. 3) Describe heterotic effects associated with breed crosses. 4) Develop unique adjustments for potential heterogeneous variances and environmental effects that may be necessary when combining pure and crossbred data.
Within the United States, the use of diverse breed resources and their crosses are key components of sheep production enterprises. Currently, however, information on crossbred performance is not incorporated into genetic evaluation of purebred sheep and objective methods to compare rams of different breeds are not readily available. These limitations impact the efficacy of selection decisions in purebreds. Such knowledge is required to properly utilize crossbred data, and data from purebred animals of different breeds, in genetic evaluation of U.S. sheep. To accomplish the objectives, cooperators will utilize existing data available from crossbreeding projects undertaken at the United States Department of Agriculture, Agricultural Research Service (USDA ARS) Range Sheep Production Efficiency Research Unit (RSPER) over the last three program cycles. Rams of multiple breeds, meat- and wool-type, were purchased from around the nation and crossed to the RSPER’s ewe base. This has resulted in an unparalleled crossbred record database, representing nearly 240 sires and their offspring’s performance for an array of economically relevant traits. Information on a fully formed Terminal-sire composite line, and an industry composite (Siremax), is also available for comparative purposes. Using quantitative genetics methods, breed effects will be determined. Based on the population’s structure, including mating design, direct and maternal heterotic effects from the various crosses will be evaluated. Since purebred sires were sourced from flocks participating in the National Sheep Improvement Program (NSIP), the crossbred data will be connected with purebred parental performance. Through this conduit, heterogeneity of variance in the combined populations will be investigated, including differential impacts of environmental factors on performance. Collectively, these results will serve as the foundation for integrating crossbred data into routine genetic evaluation. The link with NSIP will also ensure the products will be promptly transferred to industry for advancement of the profitability, quality and competitiveness of the national sheep base.