Effect Of Inositol Supplementation On Growth Performance,Glycolipid Metabolism,Digestion And Antioxidant Activity Of Grass Carp (Ctenopharyngodon Idellus)

As B vitamins,inositol is widely used in aquaculture because of its advantages in promoting lipid metabolism,improving feed utilization rate and accelerating the growth of fish.Previous studies on inositol were mostly based on purified feed,However,with the increase of the dietary lipid level of grass carp feed in practical production in recent years,the appropriate supplement of inositol in practical diets also should be adjusted.Therefore,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 25juvenile fish averaging(15±0.15)g(mean±S.E.M.)in quadruplicate aquaria for 56d,and the study of grass carp(Ctenopharyngodon idellus)in this experiment carried out the following two aspects:1.Effect of inositol supplementation for practical dietary on growth performance,digestion-absorption function and antioxidant activity of Ctenopharyngodon idellaThe results showed that:1)the final body weight(FBW),weight gain rate(WGR),specific growth rate(SGR)and feed efficiency(FE)at dietary inositol levels of100~150 mg/kg were significantly higher than that of other groups;2)With the increasing of inositol dietary level,the viscerosomatic index(VSI)and hepatosomatic index(HSI)of grass carp revealed a trend of gradual decrease,but no difference was found in condition factor(CF)among all groups;3)The supplement of inositol significantly increased crude protein and crude lipid in whole body;4)The intestinal amylase,lipase,protease,creatine kinase and Na~+,K~+-ATPase activities of fish fed the100 mg/kg were significantly promoted,and villus density and muscular thickness of foregut were markedly improved under the same level;5)Significantly higher superoxide dismutase(SOD)activities in liver,muscle and intestine was 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 for growth performance and feed conversion efficiency,promote the healthy development of intestinal tract and improve digestion-absorption function,and improve antioxidant activity of liver,muscle and intestine.FE and SGR analyzed by broken-line regression indicated that the suitable inositol supplementation for practical dietary of grass carp is 90.3~96.4 mg/kg.2.Effect of inositol supplementation for practical dietary on glycolipid metabolism metabolism of Ctenopharyngodon idellaThe results showed that:1)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 the100 mg/kg inositol diet or higher was significantly lower than the control group and group fed diets containing 50 mg/kg inositol;2)The inositol accumulation in the liver and muscle showed a trend of increased firstly and then stabilized,and reached the highest at dietary inositol levels of 200 mg/kg;3)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 descend,and all reached the maximum at dietary inositol levels of 100~150 mg/kg,except the LDL-C content.In contrast,alanine aminotransferase(ALT)and aspartate aminotransferase(AST)activities showed a trend of decreased firstly and then rise,and also reached the minimum at dietary inositol levels of 100-150 mg/kg;4)Dietary inositol supplementation resulted in markedly increase of carnitine palmityl transferase-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;5)With the increasing of inositol dietary level,the plasma glucose(GLU)content gradually increased and reached its maximum when dietary inositol was 400 mg/kg,and the accumulation of glycogen in liver and muscle showed different trends;6)The dietary inositol levels of 50-300 mg/kg could significantly affect the activities of glycolytic enzymes in the liver and muscle of grass carp.With the increase of dietary inositol level,the activities of hexokinase(HK)and pyruvate carboxylase(PK)in the liver firstly rose and then decreased,but fructose-6-phosphate kinase(PFK)and citrate synthase(CS)activities in the liver showed the opposite trend.The activity of HK in the muscle also increased firstly and then decreased,but there was no significant difference in PK activity among the groups.The PFK activity gradually decreased,and the CS activity was consistent with that in the liver.7)Fructose1,6-bisphosphatase(FBP),glucose-6-phosphatase(G-6-pase)and phosphoenolpyruvate carboxykinase(PEPCK)of liver and muscle were significantly increased at dietary inositol levels of 100-200 mg/kg.In conclusion,the appropriate dietary inositol supplementation to grass carp has an improving effect for lipid digestion,promote the capacity on the synthesis and degradation of tissue fatty acid,increase the crude lipid contents of liver and decrease that in muscle.In addition,suitable levels of inositol can promote glycolysis in the liver and muscle,but not all key enzymes can maintain a consistent feedback response.However,the gluconeogenesis process in the liver and muscles is also kept in an active state,which ultimately leads to an increase in the blood glucose concentration of grass carp...