Effects of inositol supplementation to practical dietary on growth performance, lipid metabolism and antioxidant activity of Ctenopharyngodon idella

A study was conducted to evaluate the effect of the dietary inositol levels on growth, lipid metabolism and antioxidant activity of grass carp. Seven isonitrogenous (30.78 % protein) and isolipidic (6.04% lipid) practical diets with graded levels of inositol (0, 50, 100, 150, 200, 300, 400 mg/kg) were fed to 25 juvenile fish averaging (15.00±0.15) g (mean±SE) in quadruplicate aquaria for 56 d. The results showed that the final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR) and feed efficiency (FE) at dietary inositol levels of 100–150 mg/kg were significantly higher than those of other groups. With the increasing of inositol dietary level, the crude lipid contents of whole-body and liver and lipid deposition rate significantly increased when dietary inositol was 50-300 mg/kg, but the muscle lipid content of fish fed the 100 mg/kg inositol diet or higher was significantly lower than the control group and the group fed diet containing 50 mg/kg inositol. Intestinal lipase, plasma total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterin (LDL-C), high-density lipoprotein cholesterin (HDL-C) contents and high density/low density lipoprotein cholesterin (HDL-C/LDL-C) rose in first and then declined, and all reached the maximum at dietary inositol levels of 100–150 mg/kg, except the LDL-C content. Dietary inositol supplementation resulted in marked increase of carnitine palmityl tratnsferase-I (CPT-I) and acetylCOAcarboxylase (ACC) activities in liver and muscle. Compared with the control group, the growth rate of CPT-I in liver was lower than that of ACC, while the growth rate of CPT-I in muscle was higher than that of ACC. Significantly higher superoxide dismutase (SOD) activities in liver and muscle were obtained in fish fed 100–150 mg/kg than those fed the control, and lowest malondildehyde (MDA) concentration, transaminase (AST) and alanine transaminase (ALT) activities were also found in that. In conclusion, the appropriate dietary inositol supplementation to grass carp has an improving effect on growth performance and feed conversion efficiency, promotes the capacity on lipid digestion and the synthesis and degradation of tissue fatty acid, increases the crude lipid contents of whole-body and liver and decreases that in muscle, but improves antioxidant activity of liver and muscle. FE and SGR analyzed by broken-line regression indicated that the suitable inositol supplementation to practical dietary of grass carp is 90.3–96.4 mg/kg.