THE RESPONSE OF GROWTH PERFORMANCE AND PHYSIOLOGICAL FUNCTIONS TO DIETARY CARBOHYDRATE IN CARASSIUS AURATUS VAR. PENGZE

Four isonitrogenous(35% DM) and isocaloric(16.4 kJ/g DM) diets with two types(dextrin and glucose) and two levels(20% and 40%) of carbohydrates were fed the initial weight(2.40±0.16)g Carassius auratus var.pengze for 16 weeks respectively.The fish was fed 3 times a day at 8:30,12:30 and 16:00 respectively and at each time the feed was given in trisect in order to minimize the leakage.Daily feed rations were about 4% and modulated according to the feed intake.Three replicate was performed and all the tanks were in the same close circulated system.The water temperature was kept at 25±0.5℃ during the period,the NH4+-N was lower than 0.14mg/L,the dissolved oxygen was higher than 6.0mg/L,and the nature photoperiod was followed.The fish was weighted to calculate the growth rate at the end of the 16th week.The whole fish,blood,spleen and hepatopancreas were sampled to determine spleen and hepatosomatic index(HSI),glycated hemoglobin(GHb),the antioxidant capacity and non-specific immunity.Some other carps with initial body weight of 7.14±0.85 g were reared under the similar conditions for 8 weeks to analyze the survival rate of 24h after 12.5 mg/kg body weight cadmium injected in the end.The lowest weight gain rate 586.2% was observed in fish fed diet with 40% glucose and the highest 602.6% in fish fed diet with 20% glucose.However,no significant difference was observed among groups.There was no significant difference in both spleen index and HSI,with their range from 0.28% to 0.31% and from 2.31% to 2.46% respectively.The GHb was higher in fish fed diets with high glucose(28.9 A/10gHb) and high dextrin(28.9 A/10gHb) compared to that with low glucose(26.4 A/10gHb) and low dextrin(25.1 A/10gHb)(P0.05).The hepatopancreas total antioxidant capacity(T-AOC) ranged from 1.21 U/mg protein to 1.99 U/mg protein,while the fish fed diets with glucose was higher than that with dextrin(P0.05).The activities of hepatopancreas superoxide(SOD) ranged from 270.7 U/mL to 294.3 U/mL,plasma SOD ranged from 70.1 U/mL to 85.9 U/mL,plasma T-AOC ranged from 14.0 U/mL to 17.8 U/mL,complement hemolysis(CH50) ranged from 114 U/mL to 167 U/mL,lysozyme(Lyz) ranged from 0.024 U/mL to 0.035 U/mL,and all of these indexes didn't show significant differences among groups.The erythrocyte osmotic fragility(Eof) were lower in fish fed high glucose diets(0.31 NaCl%) and high dextrin diet(0.31 NaCl%) compared to that fed low glucose diet(0.40 NaCl%) and low dextrin diet(0.36 NaCl%).The survival rate after Cadmium injected was not affected by dietary carbohydrate.These results indicated that no negative effect was appeared for carp when fed diet with 40% carbohydrate,and dietary carbohydrate could improve the antioxidant status.