Effect of dietary supplementation on growth performance, immune function, and intestinal health of hybrid grouper ( ♀ × ♂).

Introduction: The aim of this study is to investigate the effects of supplementing () on hybrid grouper ( ♀ × ♂), with a particular focus on its impact on growth performance, blood composition, intestinal antioxidant capacity, gut microbiota, tight junction protein (ZO-1) expression, and inflammatory gene expression. The study seeks to uncover the potential health benefits of C. butyricum supplementation for hybrid grouper.

Methods: The experiment included four groups: a control group (CON) and three experimental groups, each supplemented with different strains of (KM, DZN, and CLH), with a concentration of 1 × 10 colony-forming units per gram. These groups were designated as CB1 (KM), CB2 (DZN), and CB3 (CLH). The study evaluated growth performance, blood composition, intestinal antioxidant capacity, gut microbiota, ZO-1 protein expression, and inflammatory gene expression ( and ).

Result: The results indicated that supplementation with had no significant effect on body weight gain (WG), feed efficiency (FE), or body composition. However, the CB3 group significantly increased the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the intestine, as well as the expression of ZO-1. In addition, the CB3 group significantly increased serum lysozyme (LZM) activity, complement 4 (C4) levels, and immunoglobulin M (IgM) concentration, while significantly reducing the expression of pro-inflammatory genes ( and ). After supplementation with , the level of malondialdehyde (MDA) in the intestine was significantly lower than that in the control group, indicating a reduction in intestinal oxidative stress. Supplementation with also altered the composition of the gut microbiota, promoting the growth of beneficial bacteria and inhibiting pathogenic bacteria, thereby further enhancing ZO-1 expression and intestinal barrier function.

Discussion: This study suggests that supplementing has a significant immunomodulatory effect on hybrid grouper, enhancing serum immune parameters, alleviating intestinal inflammation and oxidative stress, and promoting intestinal health. Although no significant impact was observed on growth performance, the role of in improving intestinal barrier function and modulating the gut microbiota highlights its potential for enhancing fish health.