Chronic Heat Stress Affects Bile Acid Profile and Gut Microbiota in Broilers

Heat stress (HS) can inhibit the growth performance of broilers and cause substantial economic losses. Alterations in bile acid (BA) pools have been reported to be correlated with chronic HS, yet the specific mechanism and whether it is related to gut microbiota remains unclear. In this study, 40 Rugao Yellow chickens were randomly selected and distributed into two groups (20 broilers in each group) when reaching 56-day age: a chronic heat stress group (HS, 36 & PLUSMN; 1 & DEG;C for 8 h per day in the first 7 days and 36 & PLUSMN; 1 & DEG;C for 24 h in the last 7 days) and a control group (CN, 24 & PLUSMN; 1 & DEG;C for 24 h within 14 days). Compared with the CN group, total BAs' serum content decreased, while cholic acid (CA), chenodeoxycholic acid (CDCA), and taurolithocholic acid (TLCA) increased significantly in HS broilers. Moreover, 12 & alpha;-hydroxylase (CYP8B1) and bile salt export protein (BSEP) were upregulated in the liver, and the expression of fibroblast growth factor 19 (FGF19) decreased in the ileum of HS broilers. There were also significant changes in gut microbial composition, and the enrichment of Peptoniphilus was positively correlated with the increased serum level of TLCA. These results indicate that chronic HS disrupts the homeostasis of BA metabolism in broilers, which is associated with alterations in gut microbiota.

Automated summary

Heat stress can hinder the growth performance of broilers, leading to economic losses. The study found that chronic heat stress resulted in a decrease in total bile acids and an increase in cholic acid, chenodeoxycholic acid, and taurolithocholic acid in broilers. The expression of CYP8B1 and BSEP increased in the liver, while the expression of FGF19 decreased in the ileum of heat-stressed broilers. Significant changes in gut microbial composition were also observed, with the enrichment of Peptoniphilus being positively correlated with the increased serum level of taurolithocholic acid.