Dietary Bile Acid Supplementation Improves Lipid Metabolism and Selected Egg Quality Traits in Late-Phase Laying Hens Fed a High-Fat Diet and Is Associated with Alterations in Gut Microbiota

High-fat diets may improve energy supply in laying hens, but they can also increase fat deposition in the liver and contribute to fatty liver hemorrhagic syndrome (FLHS), a metabolic disorder that impairs hen health and egg production. Bile acids (BAs), which are natural compounds produced in the liver to support fat digestion and metabolic regulation, may help reduce these negative effects. This study evaluated the effects of dietary BA supplementation on production performance, selected egg quality traits, lipid-related indices, liver histology, and cecal microbiota in late-phase laying hens fed a high-fat diet (HFD). A total of 150 Hy-Line Brown laying hens at 50 weeks of age were allocated either a normal diet (ND), a HFD, or a HFD supplemented with 300 mg/kg BAs (HFD + BAs) for 5 weeks. Compared with the HFD group, BA supplementation affected average daily feed intake (ADFI) and increased the Haugh unit (HU) (p < 0.05), whereas laying rate (LR), average egg weight (AEW), feed conversion ratio (FCR), and most other egg quality traits were not significantly changed. BA supplementation was also associated with differences in selected serum and hepatic lipid-related indices. Histological observations indicated differences in hepatic lipid deposition among treatments. Cecal microbiota analysis showed treatment-associated differences in microbial composition, and correlation analysis identified associations between selected taxa and lipid-related indices. These results indicate that, under the present HFD conditions, dietary BAs were associated with changes in selected egg quality traits, hepatic lipid-related indices, and cecal microbial composition. These findings indicate that dietary BAs may improve selected egg quality traits and liver health in late-phase laying hens by regulating lipid metabolism and intestinal microbiota.