Improving fatty liver hemorrhagic syndrome in laying hens through gut microbiota and oxylipin metabolism by A potential involvement of arachidonic acid.

(), a crucial commensal bacterium within the gut, has shown connections with hepatic lipid metabolism and inflammation regulation. Nonetheless, the role of in the progression of fatty liver hemorrhagic syndrome (FLHS) remains unknown. This study aims to explore the ameliorative effects of on FLHS in laying hens, as well as its underlying mechanisms. This is the first study to employ a chicken FLHS model, combining microbiomics and oxylipin metabolomics to investigate the mechanism of action of intestinal symbiotic bacteria. Exp. 1: 40 laying hens at 25 weeks old were randomly divided into five treatment groups (eight replicates per group and one hen per replicate), including the control group (basal diet), the high-energy and low-protein (HELP) group, and the HELP group with three different levels (10, 10, and 10 CFU) of . Exp. 2: 18 chickens at 25 weeks old were randomly divided into three treatment groups (six replicates per group and one hen per replicate) including the control group (basal diet), the model group (HELP diet), and the arachidonic acid (AA) group (HELP diet with 0.3% AA). The experiment period of Exp. 1 and Exp. 2 were 8 weeks. significantly improved body weight of seventh week ( = 0.006), liver lipid degeneration, blood lipid levels (triglycerides, cholesterol, and low-density lipoprotein cholesterol;  < 0.05), and liver function (alanine aminotransferase and aminotransferase;  < 0.05) in laying hens. downregulated the expression of lipid synthesis-related genes fatty acid synthase, acetyl-CoA carboxylase, and liver X receptor α, and inflammation-related genes tumor necrosis factor α, interleukin ()-1β, , and in the liver of FLHS-affected hens ( < 0.05), while upregulating the expression of lipid oxidation-related genes carnitine palmitoyl transferase-1, peroxisome proliferator activated receptor () α, and ( < 0.05). The in-depth analysis indicated alterations in oxylipin pathways triggered by , as evidenced by changes in the expression of pivotal genes arachidonate 15-lipoxygenase, arachidonate 5-lipoxygenase ( < 0.05), subsequently causing modifications in relevant metabolites. This included a decrease in pro-inflammatory substances such as 15-oxoETE ( = 0.004), accompanied by an increase in AA ( = 0.008). regulated the homeostasis of intestinal flora by increasing the abundance of and decreasing the abundance of and ( < 0.05). The integrated analysis revealed a robust positive correlation between abundance and AA levels ( = 0.007). This relationship was corroborated through in vitro experiments. Subsequently, the beneficial effect of AA in mitigating FLHS was confirmed in laying hens with FLHS, further supported by reverse transcription-polymerase chain reaction analysis demonstrating gene expression patterns akin to intervention. This study demonstrated that exerts an anti-FLHS effect through modulation of oxylipin metabolism and gut microbiota stability, with a pivotal role played by AA.