Assessment and genetics of stress resilience in dairy cattle

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Dairy cattle are routinely subjected to a variety of stressors that negatively impact health and fertility, welfare and production. Health and climate experts predict that exposure to stressors (i.e. pathogens, fungal mycotoxins and extreme temperature events) will increase as climate conditions continue to destabilize. Since antimicrobials are now less available for preventing and treating livestock disease, there is a need to explore alternative strategies, such as genetic selection for increased stress resilience, to enhance animal health; it is anticipated that stress resilient animals will be healthier, live longer, and be more productive. In the proposed study, we plan to develop an immune stress challenge for dairy calves using microbial-associated molecular patterns (MAMPs) so that dairy cattle populations can be stress-phenotyped, which is not currently possible. This novel health phenotype will then be used to calculate heritability estimates, explore associations with other measured health and production traits, and carry out a genome-wide association study (GWAS) to identify genetic markers associated with stress responsiveness. Lastly, resilience of stress-phenotyped animals to climate-associated stressors will be assessed. Given the wide-ranging impacts of stress on animal health and production, it is anticipated that development of this stress model will allow Canadian breeding companies such as the SEMEX Alliance to carry out genomic selection to improve dairy cattle health and production well into the future.