Protective effects of inulin on high-fat feed-induced growth inhibition, oxidative stress and lipid metabolism disorders in common carp (Cyprinus carpio)

Increasing the fat content in feed can spare protein but may cause lipid metabolism disorders. Inulin can regulate lipid metabolism and improve fish health. To investigate the effects of inulin supplementation in high-fat diets on common carp ( Cyprinus carpio ), 540 fish (4.47 ± 0.07 g/fish) were randomly divided into 6 groups with three replicates each. Groups were fed diets for 8 weeks as follows: CK (8 % lipid), G0 (12 % lipid), G1 (5.00 g/kg inulin+12 % lipid), G2 (10.00 g/kg inulin+12 % lipid), G3 (15.00 g/kg inulin+12 % lipid), and G4 (20.00 g/kg inulin+12 % lipid). Results showed that inulin supplementation (10.00–20.00 g/kg): enhanced weight gain rate, specific growth rate, feed efficiency ratio, and protein efficiency ratio, mitigating the growth reduction caused by the high-fat diet ( P < 0.05). Inulin increased hormone-sensitive lipase and adipose triglyceride lipase activities in the hepatopancreas and muscle, and upregulated peroxisome proliferator-activated receptor beta and gamma mRNA expression in the hepatopancreas, alleviating high-fat diet-induced lipid metabolism disorders ( P < 0.05). Inulin elevated serum levels of lysozyme, alkaline phosphatase, complement component, and immunoglobulin M, enhanced immune function, and increased glutathione, total superoxide dismutase, and glutathione peroxidase activities in the hepatopancreas and intestine, boosting antioxidant capacity ( P < 0.05). Furthermore, inulin ameliorated high-fat diet-induced damage to hepatopancreatic and intestinal tissues. Taken together, this study suggests that inulin supplementation improved growth performance, alleviated lipid metabolism disorders, and preserved the morphological integrity of hepatopancreatic and intestinal tissues. Based on comprehensive analysis and cost-effectiveness, the optimal inulin supplementation level in a high-fat diet for common carp is 15.00 g/kg. • High-fat feed disrupts lipid metabolism, reduces antioxidant capacity in common carp. • Add 15 g/kg inulin to feed can regulates lipid metabolism in common carp.