# Effects of a Capsaicin-Based Phytogenic Solution on Intestinal Permeability, Serum Amino Acid Concentrations, and Digestibility in Heat-Stressed Growing Pigs

## TL;DR

A capsaicin-based supplement improves intestinal health and amino acid metabolism in heat-stressed pigs, without affecting amino acid digestibility.

## Contribution

The study identifies that a phytogenic solution improves intestinal integrity and post-absorptive metabolism in heat-stressed pigs.

## Key findings

- Supplementation improved markers of intestinal permeability and partially restored amino acid concentrations.
- The phytogenic solution increased gene expression of tight junction proteins in the jejunum and ileum.
- Amino acid digestibility remained unaffected despite improved intestinal health and metabolism.

## Abstract

Heat stress causes considerable damage to the production parameters of pigs. A previous report showed that a diet supplemented with a phytogenic solution containing Capsicum spp. was shown to enhance their thermal tolerance, resulting in increased nutrient consumption and more efficient nutrient utilization. Improved pig performance was associated with lowered body temperatures, enhanced heat-stress defenses, preservation of intestinal integrity, and improved post-absorptive metabolism. This study investigated whether the observed effects are associated with altered amino acid concentrations in blood, the expression of proteins regulating intestinal permeability, and improved amino acid digestibility to further elucidate the mechanism of action. Our findings showed that supplementation improved markers of intestinal permeability and partially restored amino acid concentrations, indicating improved post-absorptive metabolism. However, amino acid digestibility remained unaffected, suggesting that, in conjunction with the results of our previous study, the improved performance is related to enhanced intestinal health, antioxidant status, post-absorptive metabolism, and thermoregulatory responses at a higher level of feed intake. Overall, the tested dietary phytogenic solution may help pigs minimize some of the negative effects of heat stress by operating at multiple levels.

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.