Effects and potential mechanism of dietary vitamin C supplementation on hepatic lipid metabolism in growing laying hens under chronic heat stress.

The adverse effects of chronic heat stress (CHS)-induced fatty liver syndrome (FLS) on laying hens during the egg-producing stages have been wildly documented. However, until nowadays, the CHS responses of growing laying hens as well as its alleviating effects of vitamin C is rarely reported. In this study, 12-week-old laying hens were subjected to CHS at 36 °C for 10 h/d for 3 weeks with or without dietary supplementation of 300 mg/kg vitamin C. Results showed that CHS significantly impaired the growth performances and the liver functions of birds, as characterized by reduced feed intake and body weight, increased hepatic lipid accumulation and serum concentrations of TG, ALT and AST, as well as the abnormal expression patterns of the lipid metabolism-related genes. Vitamin C supplementation successfully mitigated the lipid accumulation, while showed no alleviating effect on the serum contents of ALT or AST, which are two key indicators of the liver functions. Metabolomic analysis based on UPLC-Q-TOF/MS identified 173 differential metabolites from the HS and HSV group samples, and they are mainly enriched in the pathways related to the cellular components, vitamin and amino acid metabolism and the energy substance metabolism. The results indicate that CHS-induced hepatic lipid deposition in growing laying hens is effectively alleviated by dietary supplementation of vitamin C, which is probably resulted from the alterations of hepatocellular metabolic patterns.