Start Date: Aug 01, 2007
End Date: Jul 31, 2012
Genetic variation among and within breeds, including allelic variation, provides a foundation for genetic improvement through selection and for management of genetic effects through crossbreeding (or mating) systems. Improvement of production efficiency and sustainability of beef cattle and sheep production systems are dependent on greater knowledge of genetic effects on fundamental traits affecting life-cycle efficiency such as fertility, prolificacy, maternal ability, offspring survival, health, longevity, and adaptation to production environments. Two broad approaches will be pursued: 1) large-scale animal experimentation and 2) development and application of statistical theory and software to support discovery and estimation of genetic effects. The first three objectives use experimental populations to provide genotypic and phenotypic data for traits known to affect life-cycle efficiency and for matching genetic resources with specific marketing and production situations. Large-scale beef cattle and sheep experiments using both quantitative and molecular approaches are planned to provide genotypic and phenotypic data for estimation of genetic effects on fundamental traits. Cattle research will emphasize multi-breed genetic evaluation, estimation of genetic parameters within breed, and structuring of populations to facilitate genomic research leading to development of DNA tests for economically important traits. A population of cattle is being developed for QTL identification that has recent ties to industry genetics, several half-sib families large enough to contribute to identifying QTL through linkage, and many smaller families and several potential origins of QTL allowing fine mapping, association analyses, and marker validation. Potential interactions of temperate and tropically-adapted cattle breeds with temperate and subtropical environments will be investigated through evaluation of F1 cows consistent with commercial production systems in the subtropical environment of Louisiana and the temperate environment of Nebraska. Sheep experimentation will focus on breed evaluation, leading to creation and development of an easy-care maternal line of hair sheep. The animal experiments will be complemented by research to develop and apply statistical technologies required for discovery, estimation, and use of genetic effects, including incorporation of genetic markers into multibreed genetic evaluations for beef cattle. The fourth objective addresses designs of experimental populations for estimation of genetic effects. Various mating plans will be simulated and evaluated for their power to detect QTL effects of various sizes, power of detecting breed-specific heterosis, and for the standard errors of other genetic effects. The final objective focuses on the development and application of statistical theory required for analysis of data and exploitation of genetic effects by livestock industries. Whole genome selection will be investigated as a method to reduce bias and improve accuracy of genetic prediction.