Effect of dietary supplementation with Clostridium butyricum on growth, intestinal microbiota, metabolome and transcriptome in a hybrid fish ( Megalobrama amblycephala ♀ × Culter alburnus ♂)

Abstract This study investigated the effects of dietary supplementation with Clostridium butyricum on the growth performance, intestinal microbiota, metabolome and transcriptome of a hybrid fish ( Megalobrama amblycephala ♀ × Culter alburnus♂ ). Experimental fish were diet supplemented with C . butyricum at 0 (control group [CG]), 4.02 × 10 8 (L), 1.66 × 10 9 CFU/kg (T), respectively, for 8 weeks feeding. The results showed that the growth performance of fish followed the trend of T > L > CG. Compared to group CG, the microbial community structure in group T shifted significantly. The relative abundance of Fusobacteriota and Cetobacterium was higher while that of Pseudomonadota , Bacillota and Plesiomonas was lower. The predicted functional abundances of biotin metabolism, D‐alanine metabolism and propanoate metabolism in the intestinal microbiota were higher in group T than in group CG. Besides, 131 DEMs were identified and mainly enriched in glycerophospholipid metabolism and beta‐alanine metabolism. In addition, transcriptome analysis showed 1479 differentially expressed genes (DEGs) were identified and mainly enriched in pentose and glucuronate interconversions, peroxisome and protein digestion and absorption. Correlation analysis showed that the dominant bacterium Cetobacterium was positively associated with fish growth performance and glycerophospholipid metabolites. These findings suggested that dietary supplementation with C. butyricum reshaped intestinal microbiota structure and influenced lipid, carbohydrate and protein metabolism, as well as the expression of genes related to carbohydrates and lipids, which may provide insights into the microbiota‐host interactions that regulate growth in hybrid fish.