Effects of short-term exposure to high ambient temperature and relative humidity on thermoregulatory responses of European (Large White) and Caribbean (Creole) restrictively-fed growing pigs

The effects of short-term exposure to high ambient temperature and relative humidity (RH) on thermoregulatory responses were studied in two consecutive experiments on a total of 12 Large White (LW) and 12 Creole (CR) growing pigs. The pigs were submitted to two or three consecutive thermal challenges over two (153 and 188 days of age; experiment 1) or three consecutive stages (97, 111, and 125 days of age; experiment 2). For each thermal challenge, the ambient temperature (T) varied daily from 22 to 34 °C between 0900 and 1500 and from 34 to 22 °C between 1500 and 2100 during five consecutive days. The RH was maintained constant at 70, 80, 90, 80, and 70%, on day 1, 2, 3, 4, and 5, respectively. The feeding level of each pig was adjusted on a BW basis to provide 1.3 of the maintenance metabolisable energy requirement. Cutaneous temperature (CT) was constant between 22 and 24 °C and increased linearly between 24 and 34 °C (+0.27 °C per °C; P 0.10). Rectal temperature (RT) decrease (P 0.10) by breed (between 30 and 32 °C) whereas the increase of RR from 28 to 34 °C was significantly lower for CR than for LW (19.0 vs. 27.6 bpm, P 0,10). La température rectale (RT) diminue entre 22 et 26 °C (–0,3 °C ; P 0,10) alors que l’augmentation du RR entre 28 et 34 °C est significativement plus faible pour les CR comparativement aux LW (19,0 vs. 27,6 ventilations par min ; P < 0,01). Pour les deux expériences, les réponses à un stress thermique aigu sont modifiées par la répétition des challenges thermiques suggérant une acclimatation des porcs au stress thermique. En conclusion, cette étude montre que le type génétique peut influencer la réponse des porcs à un stress thermique