Combined supplementation with Bacillus subtilis and tea polyphenols alleviates high-fat diet-induced fatty liver hemorrhagic syndrome in laying hens by regulating the gut-liver axis.

Fatty liver hemorrhagic syndrome (FLHS) poses a significant threat to the health and productivity of laying hens, characterized by hepatic steatosis and disrupted lipid metabolism. Bacillus subtilis (BS) and tea polyphenols (TP) have been reported to improve laying performance and modulate lipid metabolism. This study evaluated the effects of BS and TP supplementation on mitigating FLHS through physiology, microbiomic, transcriptomic, and metabolomic analyses. A total of 150 fifty-week-old laying hens were divided into three groups, with five replicates per group and ten hens per replicate: the control group (normal diet, ND), model group (high-fat diet, HFD), and treatment group (HFD + 300 mg/kg BS and 300 mg/kg TP, HFD+BS/TP). The results demonstrated that the addition of BS and TP effectively mitigated lipid metabolism disorders in laying hens consuming a high-fat diet. Supplementation with BS/TP altered the dysbiosis caused by the high-fat diet by reshaping gut microbial communities and decreasing the abundance of Collinsella and ASF356, thus restoring balance. Serum metabolomic analysis indicated that eight differentially expressed metabolites (DEMs) involved in lipid metabolism were identified. Transcriptomic analysis identified six differentially expressed genes (DEGs) linked to lipid metabolism. Both DEMs and DEGs were primarily co-enriched in progesterone-mediated oocyte maturation. Overall, our findings showed that dietary supplementation with BS/TP could alleviate hepatic metabolic disturbances associated with FLHS in aged laying hens by modulating the gut-liver axis. This underscores the considerable potential of the BS/TP as an effective feed additive for preventing and alleviating the adverse effects of a high-fat diet.