Impact of single or repeated short-term heat challenges mimicking summer heatwaves on thermoregulatory responses and performances in finishing pigs

摘要

The objectives of this study were to determine the effects of single or repeated shortheat stress (HS) challenges that mimicked summer heat waves on performance andthermoregulatory responses in finishing pigs. A total of 45 crossbred castrated males weretested in three consecutive replicates of 15 pigs. Within each replicate, pigs wereassigned to one of five treatments. Pigs in treatment group TTT were maintained inthermoneutral conditions (22 °C) for the entire experiment (45 d). Pigs in treatment groupHHH were subjected to an HS challenge (32 °C for 5 d) at 113, 127, and 141 d of age (inexperimental periods P1, P2, and P3, respectively). Pigs in treatment groups HTT, THT, andTTH were subjected to the HS challenge at 113, 127, or 141 d of age, respectively. Each5-d challenge was preceded by a 3-d prechallenge period and followed by a 7-d recoveryperiod. Pigs were housed in individual pens and fed ad libitum. HS significantly reducedaverage daily feed intake (ADFI) and the average daily gain (ADG). Expressed as apercentage of the performance observed during the prechallenge period, ADFI decreased by12%, 22%, and 26% and ADG decreased by 12%, 43%, and 72% in the HTT, THT, and TTH groups,respectively. Regardless of the experimental group, no compensatory performance wasobserved during the recovery period, suggesting that HS has a long-lasting effect onanimal performance. Pigs subjected to HS had an immediate increase in core bodytemperature (Tcore), skin temperature, and respiratory rate, all of whichgradually decreased during the HS challenge. Based on Tcore measurements,hypothermia was observed during the recovery period in each of the three experimentalperiods, especially for pigs in the HHH and the HTT groups but only during the first HScycle. Repeated exposure to HS for the HHH group resulted in heat acclimation responsescharacterized by a lower increase in Tcore and lower decrease in ADFI during P2and P3 than during P1.