Dairy cattle breeding programs should consider selection for improved health traits although defining a breeding goal that includes health traits may be difficult. Considerable genetic variability exists for most health traits in dairy cattle. The underlying genetic variability for health traits may be larger than most estimates found in the literature because of incomplete and inconsistent data recording. Appropriate economic values for many health traits are substantial. Economic values should consider direct and indirect costs (including life cycle costs). Genetic standard deviations and economic values indicate that individual health traits may be 25% (or more) as important as yield in the breeding goal. Mammary, metabolic, and locomotive health traits are the most important. Reproductive traits exhibit genetic variation and some reproductive traits may have limited usefulness for selection. Clearly, genetic change in reproduction should be monitored in dairy cattle. The challenge for geneticists is to determine how to measure health and reproductive traits or correlated traits for optimum selection programs. Index weights for yield and health traits or correlated traits can be readily calculated if one assumes that multiple trait genetic evaluations are available for selection. Correlations among measured traits and breeding goal traits are especially important for proper index construction. Genetic markers have potential for improving health traits in dairy cattle, but the complexity of most diseases and lack of data will delay discovery of useful markers.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 17. Genetics and breeding of dairy and beef cattle, swine and horses, , 81–88, 1994
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