Synergistic effects of butyrate-producing bacteria (Clostridium senegalense I5 or Paraclostridium benzoelyticum G5) and Gracilaria lemaneiformis-originated polysaccharides on the growth and immunity of rabbitfish

This study evaluated the synergistic effects of dietary butyrate-producing bacteria (Clostridium senegalense I5 (I5) and Paraclostridium benzoelyticum G5 (G5) and Gracilaria lemaneiformis-derived polysaccharide (GLP) in rabbitfish (Siganus canaliculatus). Both bacterial strains demonstrated high susceptibility to most antibiotics, salt tolerance up to 6.5 %, pH tolerance ranging from 2 to 10, and strong auto-aggregation abilities. In a 60-day feeding trial, rabbitfish were fed either commercial pelleted feed (CPF) as a control, or CPF supplemented with 0.10 % GLP and 10⁷ cfu of G5 (GPb), or 0.10 % GLP and 10⁷ cfu of I5 (GCs). GCs significantly improved growth and feed utilization compared to other diets (P < 0.05), while both GPb and GCs improved intestinal health, and digestive enzyme activity (amylase and lipase). Additionally, both GPb and GCs increased the activity of immune-related enzymes and total antioxidant capacity, while reducing malondialdehyde levels (P < 0.05). Transcriptomic analysis of liver tissue revealed differential gene expression in immune-related pathways for GCs and GPb. Fish fed GCs and GPb diets exhibited enhanced resistance against Vibrio parahaemolyticus compared to controls (P < 0.05). These findings suggest the potential of synbiotics involving I5 or G5 and GLP to improve growth, immune response, intestinal health, and disease resistance in rabbitfish, providing valuable insights for rabbitfish aquaculture.