Effects of L-arginine supplementation on ileal digestibility of amino acids and serum concentrations of free amino acids in growing pigs exposed to heat stress conditions

Damage to small intestinal epithelium related to heat stress (HS) exposure negatively affects protein digestion and amino acid (AA) absorption in pigs. Supplemental Arg appears to partially recover the small intestine epithelium integrity. The effect of supplemental Arg on apparent ileal digestibility (AID) and serum concentration (SC) of free AA (indicator of AA absorption), was conducted with 12 ileal-cannulated pigs (27.0 ± 3.1 kg) housed under HS conditions. Pigs were randomly assigned to two treatments: HS-B, pigs fed a wheat-SBM basal diet; HS-Arg, pigs fed the basal diet supplemented with 0.20% free L-Arg. Pigs received their corresponding diet for 5 days, followed by 2-days of ileal content collection. The SC of free AA was analyzed from blood collected at 2 h postprandial. Ambient temperature (AT) ranged from 28.9 to 39.3 °C. Intestinal temperature increased up to 1.6 °C during the AT peak hours compared to the lowest AT recordings. Total flow of Arg, His, Ile, Leu, Lys, Met, Phe, Trp, and Cys through terminal ileum reduced ( P < 0.05) and that of Thr, Val, Ala, and Ser tended to reduce ( P < 0.10) in HS-Arg pigs. The AID of Arg, His, Leu, Phe, Trp, and Cys increased ( P < 0.05), and Lys, Val, and Ser tended to increase ( P < 0.10) in HS-Arg pigs. The SC of Arg, His, Ile, Lys, Met, Val, Cys, Gln, Glu, Gly, Pro, ornithine, and urea was higher in HS-Arg pigs ( P < 0.05). In conclusion, supplemental Arg in diets for pigs exposed to HS conditions increased the AID and the SC of most essential AA.