Effect of dietary L-carnitine and lipid levels on growth performance, blood biochemical parameters and antioxidant status in juvenile common carp (Cyprinus carpio)

An 8-week feeding trial was carried out under controlled condition to evaluate the effect of dietary L-carnitine and lipid levels on growth performance, whole body composition, blood biochemical parameters and antioxidant status of juvenile common carp. So, six experimental diets (designated as L5C0, L5C500, L5C1000, L10C0, L10C500 and L10C1000), which contained 5 or 10% dietary lipid were supplied with or without L-carnitine at 500 and 1000 mg kg(-1). A total of fish with initial average weight of 22.65 +/- 0.13 g were randomly distributed into 18 fiberglass tanks, 10 fish per tank. Fish were fed with one of three replicates of six isonitrogenous and isocaloric diets. Results showed that supplemental dietary L-carnitine at two levels of lipid did not significantly (P > 0.05) affect growth performance and feed utilization of juvenile common carp. Fish fed the diet L10C1000 showed increased protein content and decreased lipid and ash content (P < 0.05) compared with other groups. Triglyceride and cholesterol concentrations of fish fed 10% dietary lipid increased significantly (P < 0.05) compared with fish fed 5% dietary lipid. Dietary L-carnitine decreased cholesterol and low-density lipoprotein (LDL) concentrations yet increased glucose and high-density lipoprotein (HDL) concentrations more noticeable (P < 0.05) in fish fed the diet L10C1000 compared with its own control. Also, dietary L-carnitine elevated enzymatic antioxidants (superoxide dismutase, SOD; catalase, CAT and glutathione peroxidase, GPX) yet decreased malondialdehyde (MDA) concentrations in fish fed the diets L10C1000 compared with its own control group (P < 0.05). Therefore, a use of 1000 mg of L-carnitine kg(-1) diet is essential for depress lipid peroxidation and improve body composition in diets of juvenile common carp which contained 10% lipid.