EVALUATING MITIGATION STRATEGIES TO PROMOTE RECOVERY FROM ACUTE HYPERTHERMIA IN SWINE

Heat stress (HS) is one of the consequential important problems facing the swine industry. The negative effects of HS include reduced growth performance, reproductive efficiency, and carcass quality as well as increased morbidity and mortality. Although, the swine industry has developed several abatement strategies (i.e., fans, cooling pads, sprinklers, etc.), these approaches may be ineffective in the future as global temperatures continue to rise and the frequency of more severe heat waves increases in regions where animal agriculture is prevalent. These extreme heat events put pigs (especially those approaching market weight) at risk for acute hyperthermia that can lead to death unless body temperature is rapidly returned to euthermia and thermoregulatory function is restored.Therefore, evaluating mitigation strategies to promote recovery from acute hyperthermia is of utmost importance for improving pigs’ health and well-being and ensuring profitability and food security. In four experiments, the existence of microclimates in grow-finish barns during late summer was ascertained and a rapid cooling technique using cold water dousing and feed removal to promote recovery from acute hyperthermia in pigs was evaluated. In the first study, it was determined that microclimates exist in grow-finish barns and that pigs raised in pens that were not located directly below air inlets and ventilation fans had greater body temperature and reduced feed efficiency despite similarities in the in-barn ambient temperature and relative humidity. These data exemplifythe importance of adequate ventilation systems in swine barns and the impact of microclimates on pigs’ health and productivity during warm summer months. In the second study, grow-finish pigs that did not have feed access were exposed to acute HS and then rapidly or gradually cooled. Following the acute HS and recovery phase, all pigs were maintained under thermoneutral conditions and then euthanized over three days to determine the temporal effects of the cooling treatment on body temperature and intestinal integrity. The results showed that rapid cooling following acute hyperthermia in pigswas effective in returning body temperature to euthermia more rapidly compared to gradual cooling and rapid cooling prevented further intestinal damage. Based on these results, it was hypothesized that feed removal may have played a role in the effectiveness of rapid cooling. Therefore, a third experiment was conducted in which grow-finish pigs with or without access to feed were exposed to an acute HS challenge and then rapidly cooled. This study concluded that feed access was a determinant factor in the cooling outcome, as the gastrointestinal temperature returned to euthermia during the rapid cooling period more rapidly when feed was removed. Finally, a fourth study was conducted to evaluate the effects of feed removal in the absence of rapid cooling on the systemic inflammatory response and short-term growth performance of grow-finish pigs. However, it was determined that feed removal alone did not reduce the inflammatory response as expected. Overall, these studies demonstrate the risk forgrow-finish pigs during summer heat events and the potential use of rapid cooling in combination with feed removal for promoting recovery from acute hyperthermia in pigs.