Genome-Wide Association Analyses of Biological Responses to Heat Stress in Pigs

With genetic selection for rapid, lean tissue accretion, pigs are becoming increasingly sensitive to heat stress due to their physiological limitations (dysfunctional sweat glands) to effectively dissipate heat. Increased respiration rate and reduced feed intake are immediate and conserved biological responses to heat stress in pigs and other livestock species.  Genetic differences in how animals respond to high ambient temperatures have been previously reported, but genetic factors contributing to the response variability remain ill-defined. In this study, Illumina porcine SNP Beadchips were used to genotype 236 female pigs exposed to heat stress conditions, and analyzed to detect chromosomal regions associated with biological responses measured before and after heat stress, including rectal temperature, respiration rate, feed intake and body weight loss. We identified significant SNP associations for rectal temperature on SSC12, respiration rate on SSC14 and SSC16, and feed efficiency and weight loss on SSC13. Further analyses of these detected regions will likely reveal potential candidate genes and suggest molecular mechanisms contributing to the variability in the biological response of pigs to environmentally induced hyperthermia. This work was supported by grants from the National Pork Board, Smithfield, Ensminger fund and State of Iowa and Hatch funding.