Impact of bacteroides uniformis on fatty liver hemorrhagic syndrome in dawu golden phoenix laying hens: modulation of gut microbiota and arachidonic acid metabolism

This study explored the impact of <i>Bacteroides uniformis</i> (<i>B. uniformis</i>) on fatty liver hemorrhagic syndrome (FLHS) induced by a high-energy and low-protein (HELP) diet in laying hens, mainly focusing on hepatic lipid metabolism, gut microbiota, and arachidonic acid (AA) metabolism. A total of 120 Dawu Golden Phoenix laying hens (210-day-old) were randomly divided into four groups. The control group (CON) was fed a standard diet and received a daily gavage of PBS, while the other groups were fed with a HELP diet to induce FLHS and received a daily gavage of PBS (MOD), 1 × 10⁹ CFU/ml <i>B. uniformis</i> (BUL), and 1 × 10¹¹ CFU/ml <i>B. uniformis</i> (BUH) for 70 days. All hens were administered 1 ml daily by gavage. Each group had 6 replications with 5 hens per replication. The results showed that <i>B. uniformis</i> increased the egg production rate and feed conversion ratio and decreased body weight, liver index, and abdominal fat rate (<i>p</i> < 0.05). <i>B. uniformis</i> treatment reduced liver lipid accumulation by reducing the levels of Triglyceride (TG), Total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), alanine transaminases (ALT), and aspartate transaminases (AST) in serum and significantly elevated high-density lipoprotein cholesterol (HDL-C) (<i>p</i> < 0.05). The results indicated that <i>B. uniformis</i> altered the gut microbiota. Specifically, the abundance of <i>Bacteroides</i> was higher, and the relative abundances of <i>Treponema, Helicobacter,</i> and Spirochaetota were lower than those of the MOD group (<i>p</i> < 0.05). Moreover, targeted metabolomic analysis showed that supplementation of <i>B. uniformis</i> significantly elevated 6-keto-PGF_1α and AA levels, along with significantly reduced levels of thromboxane B₂ (TXB₂), leukotriene D₄ (LTD₄), 8-isoprostaglandin F_2α (8-iso-PGF_2α), 12S-hydroxyeicosatetraenoic acid (12S-HETE), 15S-hydroxyeicosatetraenoic acid (15S-HETE), 9-S-hydroxy-octadecadienoic acid (9S-HODE), and 13-S-hydroxy-octadecadienoic acid (13S-HODE) (<i>p</i> < 0.05). In conclusion, the oral intake of <i>B. uniformis</i> can improve liver function, gut microbiota, and AA metabolism, thereby helping to ameliorate FLHS in Dawu Golden Phoenix laying hens.