Abstract
A Capsicum spp.-based phytogenic solution (PHY) improved the performance and thermal tolerance of heat-stressed (HS) growing pigs. Two trials were conducted to further evaluate the HS pig response to supplemental PHY. Trial 1: The effects on the serum concentrations of amino acids (AAs) and the gene expression of tight junction proteins in the jejunum and ileum were assessed with 42 pigs (Landrace-Hampshire-Duroc; 27.0 ± 4.5 kg BW). There were three treatments (14 replicates): pigs under thermoneutral (TN) conditions fed control diet (TN-C); and HS pigs fed control diet without (HS-C) or with PHY (HS-PHY). Trial 2: Two-period digestion trial with eight ileal-cannulated pigs to analyze apparent ileal digestibility (AID) of AAs. Period 1: All TN pigs, fed the control (TN-C) or PHY-supplemented (TN-PHY) diet. Period 2: All HS pigs, fed the same diet as in period 1 (HS-C and HS-PHY). The control diet was based on wheat-soybean meal. In the jejunum, HS-C pigs had reduced occludin gene expression (p < 0.01) compared to TN-C pigs. HS-PHY pigs increased claudin-2 and tight-junction-protein-1 gene expression compared to HS-C (p < 0.05). In the ileum, HS-C and HS-PHY pigs had reduced occludin gene expression (p < 0.01). The serum concentrations of AAs decreased in HS-C compared to TN-C pigs (p < 0.05); except for arginine and isoleucine, HS-PHY pigs partially recovered serum AA levels. HS tended to reduce (p < 0.10; lysine and methionine) and reduced (p < 0.05) the AID of essential AAs. PHY did not mitigate the HS-associated reduced AA digestibility. In conclusion, these results support the concept that a phytogenic solution improves intestinal integrity and partially restores the post-absorption metabolism of amino acids, independent of the amino acid digestibility of heat-stressed pigs.