396 Heat stress and bioenergetics in sows and their offspring: implications for growth and development.

Abstract Pork production plays a crucial role in providing high-quality nutrition to a growing population. However, rising global temperatures and more frequent and extreme weather events directly affects swine through heat stress. Advances in swine genetics, management, and nutrition have enhanced productivity, with modern pigs achieving faster and more efficient growth rates and larger litter sizes. However, these advancements are associated with greater metabolic heat production, particularly in gestating and lactating sows, reducing the thermal gradient necessary for effective heat dissipation and increasing their heat stress susceptibility. Exposure to heat stress alters metabolic efficiency, shifting energy away from productive processes and towards those necessary for survival, ultimately impacting productivity. Heat stress may also reduce maintenance energy requirements due to changes in visceral mass, feed intake, thyroid hormone levels, and energy requirements for thermogenesis. The direct impacts of heat stress on the sow can also have long-term consequences for their offspring. Developing swine fetuses are particularly vulnerable to gestating sow heat stress they rely entirely on the dam’s ability to dissipate heat. In utero heat stress not only has direct impacts on the sow’s ability to produce a viable litter, with reduced birth weights and litter sizes reported, but also alters lifetime metabolism and energy partitioning priorities in affected offspring. These phenotypic changes are likely a result of epigenetic modifications and in utero growth restriction. Together, postnatal and in utero heat stress create compounding physiological stressors that impact swine performance at multiple stages of development. Understanding the biological mechanisms underlying these bioenergetic shifts is essential for refining models that more accurately predict metabolic requirements under heat stress and for developing or improving mitigation strategies.