132 Genetics of Stress Hormone Concentrations in Hair of Healthy Nursery Pigs and Their Relationship with Back Test Responses

Abstract

Abstract Cortisol and dehydroepiandrosterone (DHEA) are circulating adrenal hormones whose concentration in the blood varies in the face of infectious and non-infectious stressors. Their incorporation into hair makes their concentration in hair a robust retrospective assessment of HPA-axis activity as a measure of the stress response of an animal over the period of hair growth. Our objective was to estimate the genetic parameters of hormone concentrations in the hair of healthy pigs and their genetic correlation with responses to the standard back-test. Hair shaved from the rump area of 871 Large White X Landrace barrows (~40 d of age) from 6 breeding companies, maintained in a high-health nursery, was analyzed for cortisol and DHEA concentrations. Behavioral responses to a 60 s standard back-test were obtained at ~26 d of age, including the number of vocalizations (VN) and struggles (SN) and the intensity of the vocalizations (VI) and struggles (SI). All pigs were genotyped with a 50K SNP panel and imputed up to 650K. Estimates of heritability of log-transformed levels of cortisol and DHEA using univariate animal models were 0.26 ± 0.08 and 0.00, respectively, while litter effects explained 0.19 ± 0.05 and 0.09 ± 0.04 of the phenotypic variance, respectively. Back-test responses were more heritable, ranging from 0.34 ± 0.08 (VI) to 0.58 ± 0.08 (VN), with small litter effects (0.00 to 0.06). Estimates of genetic correlations using bivariate animal models were high among the back-test responses, ranging from 0.58 ± 0.16 for SN-VN to 0.96 ± 0.04 for VN-VI and 0.99 ± 0.10 for SN-SI. Estimates of genetic correlations of cortisol with back-test responses ranged from low (0.08 ± 0.23 with SI) to moderate (0.66 ± 0.27 with SN). We conclude that the concentration of cortisol in the hair of healthy nursery pigs is a heritable molecular phenotype and is genetically correlated with responses to the back-test. In subsequent research, their potential as indicator traits to select for disease resilience will be investigated. This study was funded by Genome Canada, PigGen Canada, and USDA-NIFA grant # 2021-67015-34562.