Genetic and economic implications of teat and udder structure in Canadian Angus cattle
SubjectGenetic selection, Teat and Udder Score, GWAS, Cow Longevity
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AbstractIn beef herds, maintenance of favourable mammary structure is important for production efficiencies, as well as animal health and welfare. Poor teat and udder structure are associated with increased mastitis, delayed calf suckling, and early culling of cows. Despite this and evidence that teat and udder structures are moderately heritable, the Canadian Angus Association does not have a genetic evaluation for teat and udder scores. The aims of this thesis were to: 1) assess optimal animal models for estimation of genetic parameters for teat and udder scores in the Canadian Angus population, including genetic correlations with valued and commonly selected growth traits; 2) identify genomic regions and candidate genes significant to teat and udder scores in Canadian Angus cattle using weighted single step genome wide association studies (WssGWAS); 3) verify the appropriateness of a repeated measures model and explore common and distinct genomic regions and candidate genes significant towards the traits in young and mature cow groups; and 4) estimate the economic value and discounted genetic expression coefficient, and thus the economic weight for teat and udder score in Canadian Angus cattle, using both traditional bio-economic modeling as well as producer survey results using 1000minds conjoint analysis. Towards these objectives, mammary structure on Canadian Angus cows was scored using the Beef Improvement Federation recommended guidelines (1 to 9 score). Distinct approaches using single and two-trait animal models were used to determine that teat and udder score are moderately heritable (0.32 (0.06) and 0.15(0.04) respectively) in the Canadian Angus population and that it is appropriate to use visual scores from young cows to predict teat and udder score for mature cows. The WssGWAS results identified genomic regions modulating development of, gross annual remodeling of, and maintenance of mammary structure in Angus cattle. Ultimately, positive economic weights determined for teat and udder score using bioeconomic modeling and conjoint survey analysis supported the opportunity and benefit of selecting for improved teat and udder scores in Canadian Angus cattle.
CitationDevani, K. (2021). Genetic and economic implications of teat and udder structure in Canadian Angus cattle (Unpublished doctoral thesis). University of Calgary, Calgary, AB.
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