Vitamin C or ascorbic acid (ASA) is an essential micronutrient for normal growth, antioxidant capacity and immunity of fish. However, appropriate requirements of ASA for Ctenopharyngodon idella, grass carp juveniles (8.46 ± 0.19), remain unknown. For this purpose, a feeding trial of 60 days was conducted in triplicates. Six isolipidic and isoproteic diets containing 0, 25, 50, 100, 200 and 400 mg/kg of ASA were prepared. Results showed a linear increase in growth as ASA supplementation was increased from 0 to 100 mg/kg. However, a further increase in dietary ASA supplementation from 200 to 400 mg/kg resulted in a slight decrease in growth parameters. A similar trend was also recorded for the whole body, proximate composition, antioxidant enzymes and organ indices against ASA supplementation. On the contrary, fish fed with basal diet had higher thiobarbituric acid reactive substances (TBARS) content in the liver and muscles than those fed with ASA supplemented diets. ASA concentration in muscles increased in a dose-dependent manner, while ASA value was the highest in the fish fed with 100 mg/kg ASA concentration. The weight gain (WG%) data were subjected to broken-line regression analysis, and the optimal ASA requirement of grass carp juveniles was estimated to be 67.1667 mg/kg. Taken together, the inclusion of 67.1667 mg/kg of ASA is recommended in the feed of grass carp juveniles for optimum growth performance. We also recommend analysing the effect of ASA in combination with vitamin A and E.

中文翻译：

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幼草鱼（Ctenopharyngodon idella）日粮维生素C需求及其对生长属性、器官指标、全身成分和生化指标的影响

维生素 C 或抗坏血酸 (ASA) 是鱼类正常生长、抗氧化能力和免疫力所必需的微量营养素。然而，ASA 对Ctenopharyngodon idella的适当要求，草鱼幼鱼（8.46±0.19），仍然未知。为此，一式三份进行了为期 60 天的喂养试验。制备了六种含有 0、25、50、100、200 和 400 mg/kg ASA 的等脂和等蛋白质饮食。结果显示，随着 ASA 补充量从 0 增加到 100 mg/kg，生长呈线性增长。然而，日粮 ASA 补充剂从 200 到 400 mg/kg 的进一步增加导致生长参数略有下降。针对 ASA 补充剂的全身、邻近成分、抗氧化酶和器官指数也记录了类似的趋势。相反，饲喂基础日粮的鱼的肝脏和肌肉中的硫代巴比妥酸反应物质（TBARS）含量高于饲喂ASA补充日粮的鱼。肌肉中的 ASA 浓度呈剂量依赖性增加，而 ASA 值在饲喂 100 mg/kg ASA 浓度的鱼中最高。对增重（WG%）数据进行折线回归分析，估计草鱼幼鱼的最佳ASA需要量为67.1667 mg/kg。总之，建议在草鱼幼鱼饲料中添加 67.1667 mg/kg 的 ASA，以获得最佳生长性能。我们还建议分析 ASA 与维生素 A 和 E 组合的效果。