The Effects of Dietary Bacillus subtilis, Lactobacillus plantarum, and Saccharomyces cerevisiae on Growth Performance, Immune Function, and Muscle Quality in Largemouth Bass (Micropterus salmoides).

This study investigated the effects of dietary compound probiotics on growth performance, antioxidant capacity, immune response, and nutritional composition in largemouth bass (Micropterus salmoides). A total of 360 healthy fish with an average initial body weight of 30.56 ± 0.32 g were randomly assigned to three treatment groups receiving diets with 0% (control), 0.5%, or 1.0% compound probiotics for 56 days. Results showed that fish in the 0.5% and 1.0% groups had significantly higher final weight, weight gain rate, specific growth rate, and improved feed conversion ratio compared to the control (P < 0.05). Antioxidant indicators, including superoxide dismutase, catalase, glutathione peroxidase, and total antioxidant capacity, were significantly increased in both liver and intestine, while malondialdehyde levels were reduced (P < 0.05). Enzymes related to non-specific immunity, such as acid phosphatase, alkaline phosphatase, and lysozyme, were also significantly elevated (P < 0.05). Inflammatory gene expression in liver and intestine showed downregulation of pro-inflammatory cytokines and upregulation of anti-inflammatory cytokines. The expression of intestinal tight junction proteins, including claudin, occludin, and zonula occludens-1, was significantly enhanced (P < 0.05). While basic muscle composition was unchanged, beneficial shifts were observed in fatty acid and amino acid profiles, with increased levels of oleic acid, linoleic acid, phenylalanine, and lysine. These findings suggest that dietary supplementation with 0.5% compound probiotics effectively enhances growth, immunity, antioxidant function, and muscle nutritional quality in largemouth bass.