Fermented bile improved growth performance and intestine health by altering metabolic profiles and intestinal microbes in Chinese perch, <i>Siniperca chuatsi</i>

Abstract A type of fermented bile acid (BA) named 170HDa was produced using a biological method, and its impacts on growth performance, metabolism, and intestinal microbes in Chinese perch ( Siniperca chuatsi ) were investigated. Seven experimental diets were established, including treatment groups supplemented with 0.02%–0.06% 170HDa (GN1‐GN5), a positive control diet containing 0.04% commercial BAs (GN6), and a negative control diet without BA supplementation (GN7). The trial lasted for 6 weeks. Results demonstrated significant improvements ( p &lt; 0.05) in growth indicators such as final weight (FW), weight gain (WG), specific growth rate (SGR), and feed conversion ratio (FCR) in fish fed diets containing 0.02%–0.04% 170HDa compared to the control groups. Serum biochemical analyses revealed that dietary 170HDa improved lipid metabolism by significantly reducing low‐density lipoprotein cholesterol (LDL‐C) and amylase (AMS) ( p &lt; 0.05). Histopathological examination indicated that 0.02%–0.04% 170HDa‐treated fish showed more intact intestinal villi and less inflammatory damage, whereas the control group displayed notable intestinal damage characterized by inflammatory cell infiltration, lysis, and severe vacuolization. Gut microbial diversity was significantly affected by 170HDa treatment, particularly at the phylum (Proteobacteria, Tenericutes, Firmicutes, and Fusobacteria) and genus levels. Moreover, the highest activities of acid and alkaline phosphatase appeared in the GN3 group. Meanwhile, elevated levels of IL‐1β, TNFα and NF‐kB p65 were found in the 170HDa‐treated groups. These findings suggest that dietary 170HDa at a concentration of 0.02%–0.04% effectively enhanced growth performance, lipid metabolism, and intestine health in Chinese perch, potentially offering an environmentally friendly alternative to chemically extracted BAs.