Hepatic Fatty Acid Profile and Gut Microbiota Changes in Response to Dietary Bile Acid Supplementation in Late-Laying Hens

This research examined how dietary bile acids (BAs) influence hepatic fatty acid composition and cecal microbial community of late-laying hens. A total of 1080 Hy-Line Brown hens, aged 76 weeks, were randomly divided into four groups, each receiving a basal diet with 0 (CON), 200 (BA200), 300 (BA300), or 500 (BA500) mg/kg BAs for 35 days. Results showed that hepatic stearic acid (C18:0) concentrations were significantly reduced in all BAs-supplemented groups (p < 0.05). The BA300 group exhibited a significant increase in oleic acid (C18:1n9c), total monounsaturated fatty acids (MUFAs), and n-3 polyunsaturated fatty acids (PUFAs), alongside a decreased n-6/n-3 PUFA ratio (p < 0.05). Furthermore, the Chao1 index increased in all BAs-supplemented groups (p < 0.05), and the Simpson index was higher in BA300 (p < 0.05). LEfSe analysis indicated that the CON group had a higher abundance of opportunistic pathogens, while BA supplementation altered the cecal microbial composition. Notably, the BA300 group exhibited the most favorable microbial profile, characterized by enrichment of beneficial Enterococcus and improved microbial stability. In conclusion, supplementation with 300 mg/kg BAs most effectively improved hepatic fatty acid composition and cecal microbial diversity in late-laying hens, supporting its use as a nutritional strategy in the late laying phase.