Genetic and genomic approaches to improve dairy health, food quality and farm profitability through enhanced immune response

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Accurate and systematic recording of on-farm disease is subject to many environmental factors, including data recording practices, herd management and pathogen exposure. As a result, the heritability of disease traits is quite low, generally below 5%. Immune response (IR) traits, on the other hand, function to control disease and are better defined for each animal with a much higher heritability (~25%). Therefore, while disease recording is a prerequisite for the validation of any selection strategy to improve health, selection for IR is likely to be a more powerful way to increase resistance to a broad range of pathogens than direct selection for a particular disease or single pathogen. The immune system is designed to control infectious disease and individuals with robust immune response are expected to have health advantages. At the University of Guelph, researchers have developed a patented test system to identify animals with a balanced and enhanced or High Immune Response (HIR). HIR dairy cattle have been shown to be at lower risk of diseases, including mastitis, the mostly costly disease of dairy cows. HIR animals are expected to require less therapeutic intervention, including antibiotics, thereby improving milk and meat quality. The next critical step to improve understanding of the HIR technology is to perform genome-wide association studies to determine potential genetic markers associated with the various IR phenotypes and to create a reference population of cows with IR phenotypes and genotypes for genomic evaluation of immune response. The results of this study are expected to provide novel insight into the potential inclusion of immune response traits in genetic and genomic selection indices to improve inherent animal health, food quality and farm profitability.