Rectal temperature of lactating sows in a tropical humid climate according to breed, parity and season

Abstract

The effects of season (hot vs. warm) in a tropical humid climate, parity (primiparous vs. multiparous) and breed (Creole: CR, Large White: LW) on rectal temperature (RT) were studied for a total of 222 lactations obtained in 85 sows (43 CR and 42 LW; 56 primiparous and 166 multiparous) over a 28-d lactation, between lune 2002 and April 2005. Mean daily ambient temperature was higher during the hot season than during the warm season (26.0 vs. 24.1°C) and relative humidity was high and similar in both seasons (89% on average). At farrowing, BW was lower (172 vs. 233 kg) and backfat thickness was higher (37 vs. 21 mm) in CR than in LW sows (p<0.01). During the hot season, the reduction of average daily feed intake (ADFI) was more pronounced in LW than in CR sows (-920 vs. -480 g/d, p<0.05). Rectal temperature was higher at 1200 than at 0700hr, which coincides with the maximum and the minimum values of daily ambient temperature. The daily RT increased (+0.9°C; p<0.01) between d -3 and d 7 (d 0: farrowing day), remained constant between d 7 and d 25 and decreased (p<0.01) thereafter (i.e. -0.6°C between d 25 and d 32). The average daily RT was significantly higher during the hot than during the warm season (38,9 vs. 38.6°C; p<0.01). It was not affected by breed, but the difference in RT between the hot and warm seasons was more pronounced in LW than in CR sows (+0.4 vs. +0.2°C; p<0.05). Parity influenced the RT response; it was greater in primiparous than in multiparous sows (38.9 vs. 38.7°C; p<0.01). This study suggests that thermoregulatory responses to heat stress can differ between breeds and between parities.