Evaluating and mitigating the effects of in utero heat stress on postnatal performance and stress response of swine
In utero heat stress (IUHS) is a major concern for realizing full production potential in the swine industry. Postnatal phenotypes, such as growth performance, post-absorptive metabolism, and stress response, are negatively altered in pig offspring that have been exposed to IUHS. With current trends in global temperatures predicting a continuation of increased temperatures, it is necessary to further investigate mechanisms driving these altered postnatal phenotypes and to find mitigation strategies to combat the negative effects of IUHS. In a first study, postnatal consequences of IUHS in pigs were evaluated and a mitigation strategy was tested. A second study was conducted to investigate the HPA axis response to a stress challenge in IUHS pigs. The first study found decreased average daily gain in IUHS pigs, and that providing a nutrient-dense diet did not rescue this lost productivity due to a decrease in feed intake for this diet. These results show the importance of maintaining beneficial gestation environments to avoid IUHS and the need to continue looking for alternative strategies to mitigate negative effects of IUHS. In the second study, IUHS pigs had a decreased change in cortisol response (Δ CORT) from baseline when subjected to a corticotropin-releasing hormone (CRH) challenge at 10 wk of age, and 15 wk old pigs had a decreased Δ CORT response when subjected to a dexamethasone suppression test and a CRH challenge as well as decreased glucocorticoid receptor expression in both the hypothalamus and anterior pituitary when compared to 10 wk old pigs. These results show changes in HPA axis function as young pigs mature and that particular focus may need to be put on IUHS pigs at a young age when they might be more vulnerable to negative impacts of stress. Overall, these studies show that IUHS causes a variety of negative postnatal effects in offspring and that a better understanding of mechanisms driving these changes along with developing alternative strategies to combat the incidence of these negative postnatal effects remains of paramount importance for the swine industry.