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970
Effect of heat stress on the apparent and standardized ileal digestibilities of amino acids in growing pigs
The exposure of pigs to heat stress (HS) impairs the small intestine digestive and absorptive capacities affecting in turn the AA digestibilities. A two 7-d periods experiment was conducted with 8 pigs (30 kg initial BW) surgically fitted with T-type cannulas at the terminal ileum to analyze the effect of HS on both the apparent (AID) and the standardized ileal digestibility (SID) of AA in pigs fed a wheat-SBM diet. A thermometer was placed inside the ileal lumen (IL) 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 7d under thermal neutral (TN) conditions (22 ± 2 °C). Following, the pigs were divided into 2 groups (4 pigs each); one was kept under TN conditions and the other group was exposed to natural HS (24 to 45 °C) for 7d (period 1). In period 2, the ambient temperature conditions of the two groups were switched. Ileal digesta was continuously collected during 12 h on d 7 of each period. Chromic oxide was used as indicator of the intestinal digesta flow. The IL temperature was around 1.6°C higher in HS pigs (P < 0.001). The AID of AA (%) for the TN and HS pigs were: Arg, 90.6, 88.1; His, 88.7, 85.9; Ile, 84.8, 83.9; Leu, 86.9, 84.1; Lys, 86.8, 86.2; Met, 89.8, 89.1; Phe, 86.0, 84.8; Thr, 75.7, 74.1; Val, 82.8, 81.7, respectively. The SID (%) of AA for the TN and HS pigs were: Arg, 94.0, 92.0; His, 92.5, 90.2; Ile, 89.5, 88.1; Leu, 90.1, 88.6; Lys, 91.0, 90.1; Met, 94.4, 93.6; Phe, 90.4, 88.9; Thr, 86.0, 83.7; Val, 88.1, 86.5; respectively. The AID of Arg and His was lower (P < 0.01) in HS pigs, and the SID of Arg and His, as well as Leu, was also lower in HS pigs. Neither the AID nor the SID of the remaining essential AA was affected by HS. In summary, these data show that ileal temperature increases in HS pigs, and that the digestibilities of essential AA are differentially affected in pigs exposed to natural HS conditions. Special attention should be given to Arg and His when formulating diets for growing pigs under HS conditions
Keywords: pigs, heat stress, amino acids, digestibility