Lactobacillus plantarum and Bacillus licheniformis Ameliorate High-Carbohydrate–High-Fat-Induced Glycolipid Disorders in Common Carp in Association With the Gut Microbiota and Bile Acid Axis

High-carbohydrate–high-fat (HCHF) diets help reduce feed costs in intensive aquaculture, but they often induce glycolipid metabolic disorders and hepatopancreatic steatosis in farmed fish. Although probiotics have shown promise in ameliorating metabolic disorders, the mechanisms by which they interact with the gut microbiota–bile acid (BA) axis in fish remain poorly understood. In this study, common carp were fed an HCHF diet to establish a glycolipid disorder model, followed by dietary supplementation with Lactobacillus plantarum (LP) and Bacillus licheniformis (BL) for 8 weeks. Multiomics approaches, including 16S rRNA sequencing, targeted BA metabolomics, and untargeted intestinal metabolomics, were integrated with phenotypic, biochemical, histomorphological, and molecular analyses. HCHF feeding significantly promoted growth but was associated with systemic glycolipid dysfunction. Probiotic supplementation improved glycolipid profiles and antioxidant capacity, alleviated hepatopancreatic lipid accumulation and damage, and activated the hepatic farnesoid X receptor (FXR)/small heterodimer partner (SHP) signaling pathway. Both probiotics reshaped the gut microbiota by enriching the fish-specific beneficial bacterium Cetobacterium somerae and taxa with potential bile salt hydrolase activity, while also modulating key intestinal metabolic pathways. Notably, BL exerted a more pronounced regulatory effect on BA profiles. These findings suggest that LP and BL alleviate HCHF-induced glycolipid disorders in common carp, with the gut microbiota–BA axis serving as a potential key regulatory node, providing a theoretical basis for probiotic application in functional aquafeeds.