The Genetic Impact of Stress Responsiveness and Disease Susceptibility in Pigs

126 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2005.Stress can impact various aspects of the immune system by either stimulating or suppressing the specific immune response initiated by the stressor. The experiment described in chapter 1 was designed to evaluate the impact of five breeds of pigs at three different ages on aspects of the innate immune system, cortisol (CORT) concentrations, and performance measures. Overall, there was a significant breed x age interaction for CORT, immunoglobulin G, phagocytosis (PHAGO), chemotaxis (CHTX), and performance measures. The experiment in chapter 2 was designed to determine the impact of subjecting three breeds and two commercial lines of pigs to stressors for 14 continuous days on various aspects of the innate immune system, CORT, and performance measures and the impact social status has on these responses. Pig breed or pig line did not influence the immune response to the stressors imposed in this study, but stress affected CORT, lymphocyte proliferation (LPA), and natural killer cytotoxicity (NK). Furthermore, among stressed-pigs, social status influenced total white blood cell counts (WBC), NK, and PHAGO. The experiment described in chapter 3 was designed to determine the effect of heat stress and social status on the immune response and performance of pigs infected with porcine reproductive and respiratory syndrome (PRRS) virus. Total WBC, CORT, macrophage sub-populations, PHAGO, and performance measures were different in pigs infected with PRRS compared to non-infected pigs. Heat stress influenced CORT and performance measures of pigs. However, PRRS and heat stress did not have an additive impact on the immune responses assessed in this study. Furthermore, pig social status affected body weight, macrophage sub-populations, interferon-gamma, LPA, and NK. In conclusion, there are baseline differences in the immune status among different breeds of pig but pig breed does not apparently influence the immune responsiveness to stressors imposed for 14-d. Heat stress does not appear to have an additive negative affect on the immune responsiveness of young pigs to PRRS. However, social status consistently influenced the immune responsiveness of pigs to both stressors and PRRS. Thus, implying that social status, and type and duration of a stressor are important factors that influence the immune response of a pig.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD