Effect of feed intake level on the body temperature of pigs exposed to heat stress conditions.

Feed intake (FI) level affects body heat production in thermo-neutral pigs; exposure of pigs to heat stress (HS) also increases body temperature (BT). However remains unclear whether the FI level affects the heat production of HS pigs. This study analyzed the effect of FI level on BT of 9 HS pigs (46.3 ± 2.6 kg body weight) implanted with a thermometer set to register the BT at 5-min intervals into the ileum. Pigs were divided in two groups randomly allotted to two FI treatments: high FI (HFI, 1.20 kg/d), and low FI (LFI, 0.96 kg/d), according to a two-period crossover experimental design. Pigs were fed 3-times a day (0600, 1200, and 2200 h), same amount each time (400 g or 320 g). Ambient temperature (AT) ranged from 29.0 to 35.4 °C. The BT of both HFI and LFI pigs followed a similar pattern along a 24-h period, but the BT of HFI pigs was higher than that of LFI pigs (P < 0.05). Postprandial afternoon and evening BT was higher than that after the morning meal (P < 0.05). The postprandial BT increment differed between meal times and AT, but not between FI levels. The BT of HFI and LFI pigs increased up to 0.18 and 0.22 °C, 0.60 and 0.61 °C, and 0.24 and 0.35 °C after the morning, afternoon, and evening meal, respectively, compared with the preprandial BT (P < 0.05). Hence, the dissipation capacity of feeding-related body heat appears to depend on the thermal load of HS pigs before consuming their meals; presumably, the thermal load during 6-h before the morning meal (AT below 32 °C) was lower than before the evening meal (AT above 32 °C). In conclusion, FI level affects the postprandial BT of HS pigs and its magnitude is larger after the evening and afternoon meals. These data suggest that HS pigs may reduce the voluntary FI during the afternoon and evening hours.