Effect of heat stress and GlyNAC supplementation on jejunal morphology, hepatic inflammation infiltration and distribution of GSH content in chickens

The present study evaluated the effects of cyclic heat stress (cHS) and diets supplemented with a combination of glycine and N-acetylcysteine (GlyNAC) on growth performance, serum antioxidant capacity and glutathione (GSH) content in serum, liver and pectoral muscles of Cyan-shank partridge chickens. Sixty-four male chickens (60 days old) were selected and randomly divided into four groups: CON + TN (basal diet; TN, thermoneutral condition with continuous 25 °C), GlyNAC + TN (basal diet + GlyNAC; TN), CON + cHS (basal diet; cHS, 32 °C for 4 h daily), and GlyNAC + cHS (basal diet + GlyNAC; cHS). The experimental period was 7 days. Results indicated that cHS significantly increased rectal temperature of chickens during heat treatment period (P < 0.05). Nevertheless, neither cHS nor GlyNAC supplementation affected growth performance or serum malondialdehyde levels. GlyNAC supplementation increased the GSH content in serum, liver and pectoral muscle (P < 0.05), but neither cHS nor GlyNAC altered jejunal GSH levels. The cHS decreased the ratio of villous height to crypt depth (V:C) and increased hepatic inflammatory infiltration score (IIS), while GlyNAC supplementation improved both the V:C ratio and hepatic IIS (P < 0.05). In liver, cHS downregulated the protein expression of caspase 3 and glutamate-cysteine ligase modifier subunit (GCLM), as well as the mRNA expression of GCLM gene. In contrast, GlyNAC supplementation upregulated hepatic caspase 3 protein expression and the mRNA expression of GCLM genes (P < 0.05). In conclusion, dietary GlyNAC supplementation maintained the elevated GSH content in both serum and liver, while alleviating cHS-induced impairment of jejunal integrity and hepatic inflammatory infiltration.