饲料维生素C含量对圆斑星鲽幼鱼抗氨氮胁迫能力的影响

Effects of Dietary Vitamin C Content on Anti-Ammonia-Nitrite Stress Ability of Juvenile Spotted Halibut(Verasper variegatus)

氨氮污染是水产养殖中重要的污染物,因此提高鱼体抗污染应激能力至关重要。本试验采用不同维生素C含量的饲料饲喂圆斑星鲽幼鱼,探究饲料维生素C含量对圆斑星鲽幼鱼抗氨氮胁迫能力的影响。试验在（12.5±1.5）℃的水温下进行,选择体重为（38.0±0.8）g的健康圆斑星鲽幼鱼,随机分为7组（每组3个重复,每个重复30尾）,分别投喂维生素C含量为10.2（对照）、249.1、402.8、616.2、769.5、909.4和1 177.8 mg/kg的试验饲料8周。投喂试验结束后,从每个重复取10尾鱼,用20 mg/L的氨氮胁迫24 h。结果表明：无论是氨氮胁迫前还是氨氮胁迫后,在饲料维生素C含量达到769.5 mg/kg时,肝脏和肌肉中维生素C积累达到饱和,再继续升高饲料维生素C含量,肝脏、肌肉中维生素C含量不再显著升高（P〉0.05）。除1 177.8 mg/kg维生素C组外,无论是氨氮胁迫前还是氨氮胁迫后,各维生素C添加组圆斑星鲽幼鱼血清中过氧化氢酶（CAT）和超氧化物歧化酶（SOD）活性均显著高于对照组（P〈0.05）。除616.2 mg/kg维生素C组血清中CAT活性无显著变化（P〉0.05）外,氨氮胁迫使各组血清中CAT和SOD活性显著降低（P〈0.05）,但添加维生素C可以减少降低的幅度。无论是氨氮胁迫前还是氨氮胁迫后,各维生素C添加组鳃丝Na^＋/K^＋-ATP酶活性均显著高于对照组（P〈0.05）。氨氮胁迫使对照组及909.4和1 177.8 mg/kg维生素C组鳃丝Na^＋/K^＋-ATP酶活性显著降低（P〈0.05）,其他组则无显著变化（P〉0.05）。氨氮胁迫使各组血清中葡萄糖和乳酸含量显著升高（P〈0.05）,对照组血清中皮质醇含量显著升高（P〈0.05）。此外,氨氮胁迫使各组血清中总铁结合力显著降低（P〈0.05）。综合各项测定指标,圆斑星鲽幼鱼饲料中维生素C含量在402.8~616.2 mg/kg时可有效提高机体抗氨氮胁迫能力。

Ammonia-nitrogen pollution is one of the important pollutants in aquaculture,thus improving the resistance of pollution stress of the fish is very important.This experiment using different vitamin C content diets to feed juvenile spotted halibut（Verasper variegatus）,in order to get the effects of dietary vitamin C content on anti-ammonia-nitrogen stress ability of juvenile spotted halibut.Water temperature was maintained at（12.5±1.5）℃ in this experiment.Juvenile spotted halibut with the body weight of（38.0±0.8） g were randomly assigned into 7 groups with 3 replicates per group and 30 fish per replicate,and fed 7 experimental diets with the vitamin C content was 10.2,249.1,402.8,616.2,769.5,909.4 and 1 177.8 mg/kg,respectively.The experiment lasted for 8 weeks.After feeding trial,each replicate selected 10 fish to stress 24 h by 20 mg/L ammonia-nitrogen.The results showed as follows：whether before or after ammonia-nitrite stress,the vitamin C accumulation in muscle and liver reached saturation when dietary vitamin C content was 769.5 mg/kg,and continued to rise the dietary vitamin C content,the vitamin C content in muscle and liver was not significantly increased（P〉0.05）.The activities of serum catalase（CAT） and superoxide dismutase（SOD） in vitamin C addition groups except 1 177.8 mg/kg vitamin C group were significantly higher than those in control group whether before or after ammonia-nitrite stress（P〈0.05）.The activities of serum CAT and SOD in groups except serum CAT activity in 616.2 mg/kg vitamin C group were significantly decreased by ammonia-nitrite stress（P〈0.05）,and decline ranges in vitamin C addition groups were less compared with control group.The gill Na^＋/K^＋-ATPase activity in vitamin C addition groups was significantly higher than that in control group whether before or after ammonia-nitrite stress（P〈0.05）.The gill Na^＋/K^＋-ATPase activity in control group and 909.4,1 177.8 mg/kg vitamin C groups was significantly decreased（P〈0.05）,but that in other groups had no significant change after ammonia-nitrite stress（P〉0.05）.Ammonia-nitrite stress significantly increased the contents of serum glucose and lactic acid in all groups（P〈0.05）,and significantly increased the serum cortisol content in control group（P〈0.05）,while significantly decreased the serum total iron binding capacity（TIBC） in all groups（P〈0.05）.Base on a comprehensive consideration of various measured indices,when dietary vitamin C content is 402.8 to 616.2 mg/kg,the anti-ammonia-nitrogen stress ability of juvenile spotted halibut can be effectively improved.