Dietary yeast culture supplementation enhances feed utilization in largemouth bass (Micropterus salmoides) via promotion of metabolic homeostasis and hepatointestinal health

As a complex compound, yeast culture provides not only abundant proteins and amino acids, but also immunologically active components such as β-glucan, nucleotides, and mannose oligosaccharides. This study aimed to investigate the effects of dietary supplementation with yeast culture on the growth performance, metabolism, and hepatointestinal health of largemouth bass ( Micropterus salmoides ). Juvenile largemouth bass (initial body weight: 31.39 ± 0.05 g, n = 120) were randomly divided into two groups and reared for 65 days: a control group (Con) and supplemented with 3 % yeast culture on the basis of control group (YC). The results showed that although yeast culture supplementation did not significantly affect growth performance ( P > 0.05), it significantly reduced the feed conversion ratio (FCR) and increased the productive protein value (PPV) ( P < 0.05), indicating improved economic benefits. Fish fed YC diet enhanced the fasting glycolysis, gluconeogenesis, key lipolytic enzymes, and the basal energy metabolism ( P < 0.05), which contributed to the protection of the liver from lipid accumulation. Additionally, addition of yeast culture reduced inflammatory infiltrated intestines and downregulated the expression of HIF1α and IL-10 ( P < 0.05). It also promoted intestinal health by reducing the abundance of harmful bacteria and increasing beneficial microbes. In conclusion, yeast culture improves hepatointestinal health by modulating glucose and lipid metabolism, as well as optimizing the gut microbiota composition, leading to enhanced feed utilization and economic benefits. • Yeast culture can lower the feed conversion ratio and improve economic efficiency, without impairing growth performance. • Yeast culture regulates glucose and lipid metabolism, offering protection to the liver against fat accumulation. • Yeast culture reduced harmful bacteria and increased beneficial microbes, effectively alleviating intestinal inflammation.