Theses and Dissertations Collection

Protecting and improving production, health and breed diversity are important goals in animal management and conservation. Sheep are a globally important species that contribute meat, milk and fiber to local communities and economies, but production can be jeopardized by poor genetic potential for traits of interest, genetic disease susceptibility, and consequences related to diminished genetic diversity (e.g., inbreeding depression). There remains a need within the sheep genetics community for better characterization of the relationship between genetic variants and production quality traits, improved understanding of the genetic mechanisms which may confer disease resistance or susceptibility, and insights into the genetic signatures resulting from past selection history and unique breed characteristics. The work presented in this dissertation aims to contribute to ongoing efforts to address these concerns. To this end, genome-wide association studies (GWAS) were employed to identify single nucleotide polymorphism (SNP) markers associated with economically relevant wool quality characteristics and susceptibility to angular limb deformity (Rambouillet rams) and susceptibility or resistance to gastrointestinal nematode infection (Katahdin sheep). Inbreeding and genetic diversity were evaluated for Rambouillet, Katahdin and Dorper breeds, and runs of homozygosity and Wright’s fixation index analyses were utilized to identify signatures of selection in these sheep. The work presented within this dissertation addresses areas of current interest and contributes important insights into the contribution of genetics to wool production and disease risk in sheep, and identified signatures of selection which may harbor genes of interest in three popular United States breeds.