The exposure of pigs to heat stress impairs the small intestine digestive and absorptive capacities affecting in turn the AA digestibilities. Two seven-day experiments were conducted with cannulated pigs to study the effect of heat stress on both the apparent (AID) and the standardized ileal digestibility (SID) of amino acids in pigs fed a wheat-SBM diet. A thermometer was placed inside the ileal lumen of all pigs to register the temperature at 15 min intervals. After recovery from surgery, all pigs were adapted to the diet and trained to consume the same amount of feed twice a day for seven days under thermal neutral conditions (22 ± 2°C). Following, the pigs were divided into two groups (four pigs each); one was kept under thermal neutral conditions and the other group was exposed to natural heat stress (24 to 45°C) for seven days. Then the ambient temperature conditions of the two groups were switched. Ileal digesta was continuously collected during 12 hours on day seven of each period.
The results indicated that the AID of arginine and histidine was lower in the heat stressed pigs, and the SID of arginine and histidine, as well as leucine, was also lower in heat stressed pigs. Neither the AID nor the SID of the remaining essential amino acids was affected by heat stress. These data show that ileal temperature increases in heat stressed pigs and that the digestibilities of essential amino acids are differentially affected in pigs exposed to natural heat stress conditions. The researchers indicated that special attention should be given to arginine and histidine when formulating diets for growing pigs under heat stress conditions.