Evaluation of pigs’ susceptibility to summer heat waves based on continuous measurement of body temperature

The aim of this study was to categorise the heat acclimation response patterns of growing–finishing pigs subjected to acute heat stress induced experimentally. This classification was based on continuous core body temperature ( BT ) measurements. These data have been originated from six experimental trials, all of which were designed to assess the effects of a stress situation simulating a summer heatwave on pig performance and physiological responses. The pigs (Large White × Landrace × Pietrain; n = 186) were housed either individually (five trials) or in small groups (one trial) in temperature-controlled rooms. In each trial, the pigs were kept under thermoneutral conditions (an average of 22 °C) for at least 7 days prior to being subjected to an acute heat stress situation lasting four to five consecutive days at an average temperature of 32 °C. Throughout the trials, the pigs had free access to feed and water. Core BT patterns were modelled using spline smoothing functions. All pigs showed an immediate rise in core BT during the first 24 h of heat exposure, followed by a gradual decline during the acclimation phase. An analysis pipeline was developed to extract mean, trial-specific, and individual-specific variations from raw core BT data. On the basis of individual variations in core BT, our non-supervised clustering approach distinguished three groups of pigs with divergent temperature responses to the heat challenge. Cluster 1 (n = 97) exhibited a moderate BT increase during the first 48 h with limited acclimation. Cluster 2 (n = 42) showed a sharp initial rise followed by a significant decline, reflecting strong heat acclimation. Cluster 3 (n = 36) displayed a gradual BT increase during the first 48 h with no clear acclimation over the subsequent 3 days. These groups also differed in their circadian variation in core BT during the challenge, as well as in their voluntary feeding patterns before and during the thermal challenge. Taken together, these results provide valuable insights into the different physiological strategies used to cope with acute heat stress.