The effect of dietary supplementation with Lactobacillus rhamnosus GCC-3 fermentation product on gut and liver health of common carp (Cyprinus carpio)

This study investigated the effects of Lactobacillus rhamnosus fermentation products added to feed on common carp (Cyprinus carpio) on growth, gut and liver health, and gut microbiota. Common carp with an average weight of 1.95±0.4 g were fed five experimental diets: normal diet (normal) and normal diet supplemented with Lactobacillus rhamnosus fermentation products (abbreviation: 0.2% GCC-3, 0.3% GCC-3, 0.4% GCC-3 and 0.5% GCC-3, respectively) for 8 weeks. The results showed that the GCC-3 fermentation product did not affect the growth phenotype of common carp. The diet supplemented with 0.3% GCC-3 significantly reduced the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels of common carp compared to the control group. Diets with GCC-3 fermentation products significantly reduced liver triacylglycerol (TAG) levels. Diets supplemented with 0.3% GCC-3 fermentation products significantly downregulated the expression of liver liposynthesis gene (fas) and significantly upregulated the expression of liver lipolysis gene (cpt1). Diets supplemented with GCC-3 significantly reduced the serum lipopolysaccharide (LPS) levels of common carp compared to the control group. In addition, dietary supplementation with 0.3% GCC-3, 0.4% GCC-3, or 0.5% GCC-3 all increased the abundance of Cetobacterium and decreased the abundance of Acinetobacter. In summary, dietary supplementation with 0.3% GCC-3, 0.4% GCC-3, and 0.5% GCC-3 reduced liver lipid deposition, and improved gut microbiota homeostasis of common carp. The best positive effect was observed in common carp fed a 0.3% GCC-3 supplemental diet.