8 Gestational Heat Stress: Implications for Pregnancy Success and Offspring Development in Swine

Abstract Gestating sows are particularly sensitive to heat stress due to their large mass and greater metabolic heat production associated with increased reproductive organ and fetal development. Unfortunately, the heat stress sensitivity of gestating sows has increased over the past decades due to genetic and genomic advances that have improved litter sizes and reproductive efficiency. When combined with the greater frequency and severity of heat waves and high temperatures, it is likely that reproductive issues associated with heat stress exposure will continue to be a concern for the swine industry. It is well understood that high temperatures pose a challenge to gestating sows and their developing offspring. Research from 50 to 60 yr ago demonstrated that heat exposure results in a decrease in viable embryos and an increase in embryonic mortality, particularly when gestating sows are subjected to heat stress in the first trimester. Additionally, late gestation heat stress exposure can increase the rate of stillborn piglets and reduce the total number of liveborn piglets. Although the reasons for these losses are multifactorial, the direct influence of maternal body temperature and total stress load on the intrauterine environment can play a significant role during these critical stages. For offspring that survive to birth, prospects for a healthy, productive, and stress-free life are at risk due to the long-lasting effects of in utero heat stress, which include greater postnatal stress sensitivity and decreased productivity. Therefore, understanding and mitigating gestational heat stress in pigs is of great importance to ensure the sustainability and profitability of swine production.