THE RESPONSE OF GROWTH PERFORMANCE AND PHYSIOLOGICAL FUNCTIONS TO DIETARY CARBOHYDRATE IN CARASSIUS AURATUS VAR. PENGZE
饲料糖对彭泽鲫生长和生理机能的影响

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 vat. 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 16~(th) 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) (P<0.05). 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 (P<0.05). 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.