Dietary porcine bile acids alleviate hepatic lipid dysregulation and fatty liver syndrome in aged laying hens fed high-energy low-protein diets

Fatty liver syndrome (FLS) in aged laying hens is characterized by excessive hepatic lipid accumulation and impaired performance. This study evaluated the effects of dietary supplementation with a porcine bile-derived bile acid (BA) product (containing 19.9% goose-derived deoxycholic acid and 77.2% porcine BAs) on hepatic lipid dysregulation and the development of FLS in aged laying hens fed a high-energy low-protein (HELP) diet. A total of 384 Hy-Line Brown laying hens (75 week of age, baseline laying rate approximately 72%) were randomly allocated to a 2 × 2 factorial arrangement with four dietary treatments: a control diet (11.29 MJ/kg metabolizable energy [ME], 16.5% crude protein [CP]) or a HELP diet (12.56 MJ/kg ME, 13.0% CP), each supplemented with or without 100 mg/kg BAs. The experiment was conducted over the late laying period, and data were analyzed using a two-way ANOVA to assess the main effects of diet, BA supplementation, and their interaction. Compared with the HELP group, the HELP + BAs group exhibited significantly improved laying performance, as evidenced by increased egg production, enhanced feed efficiency, and higher eggshell density ( P < 0.05). In the liver, a significant interaction between HELP diet and BAs supplementation was observed ( P < 0.05). Compared with the HELP group, the HELP + BAs group also showed a significant reduction in hepatic lipid accumulation, as evidenced by decreased lipid droplet deposition and lower hepatic triglyceride and total cholesterol levels ( P < 0.05). Moreover, BAs increased hepatic carnitine palmitoyltransferase-1 (CPT1) activity while suppressing fatty acid synthase (FAS) activity and this also involved interactions ( P < 0.05). Gene expression analysis showed that, compared with the group without BAs supplementation, BA supplementation downregulated the key lipogenic genes ( FASN and ACC ), with a significant interaction observed between the HELP diet and BA supplementation ( P < 0.05). In addition, BA supplementation regulated the expression of genes involved in BA and lipid metabolism ( PPARγ , LRH-1 , and CYP7A1 ) ( P < 0.05). In addition, BA supplementation enhanced hepatic protein expression of p-AMPK and p-ACC ( P < 0.05). Taken together, these results suggest that dietary BA supplementation effectively alleviates HELP-induced FLS in aged laying hens by inhibiting hepatic lipogenesis and promoting fatty acid oxidation. This effect is likely to improve both liver health and egg production performance.