Effects of Bacillus coagulans on growth performance and intestinal mucosal barrier functions of juvenile channel catfish (Ictalurus punctatus)

To investigate the effects of Bacillus coagulans on growth performance and intestinal mucosal barrier functions of juvenile channel catfish ( Ictalurus punctatus ), this study formulated two experimental diets: a control diet (CN group, without B. coagulans ) and a B. coagulans -supplemented diet (BC group, containing 1×10 8 CFU/g B. coagulans ). Each diet was assigned to three replicate tanks for an 8-week feeding trial. Compared with the CN group, the BC group exhibited a significantly lower feed conversion ratio ( P < 0.05). The BC group exhibited significantly increased activities of intestinal trypsin, α-amylase, and glutathione S-transferase ( P < 0.05), alongside significantly reduced levels of malondialdehyde and superoxide anion ( P < 0.05). Moreover, the BC group showed significantly upregulated gene expression of intestinal tight junction proteins ( zonula occludens-2 , claudin-18 , claudin-g , junctional adhesion molecule-2b , and junctional adhesion molecule-3b ; P < 0.05) and the anti-inflammatory factor ( transforming growth factor-β ; P < 0.05). Conversely, the gene expression levels of pro-inflammatory factors ( interleukin-1β , tumor necrosis factor-α , interleukin-6 , and interferon-γ1 ) were significantly downregulated ( P < 0.05). Additionally, genes associated with the intestinal chemical barrier ( mucin-4 , lysozyme-c , lysozyme-g , NK-lysin type 1 , and β-defensin ) were significantly upregulated ( P < 0.05). Intestinal microbiota analysis revealed increased relative abundance of beneficial bacteria (e.g., Firmicutes, Bacilli, Erysipelotrichales, and Turicibacter ) in the BC group ( P < 0.05). Non-targeted metabolomics further indicated significantly elevated levels of beneficial metabolites, including soyasaponin I and taurine in the BC group ( P < 0.05). In summary, dietary B. coagulans improved feed utilization, enhanced intestinal digestive and antioxidant capacity, strengthened mucosal barrier functions, optimized intestinal metabolism, and promoted intestinal health.