Vitamin C is an essential micronutrient for normal physiological and immune functions of fish. However, its requirements and effects in Chu's croaker (Nibea coibor) are currently unknown. A 56-day feeding trial was conducted to evaluate the optimal dietary vitamin C requirements based on its effects on growth performance, body composition and biochemical parameters in juvenile Chu's croaker (14.17 ± 0.1 g). Six isoproteic (450 g/kg crude protein) and isolipidic (100 g/kg crude lipid) diets were formulated to contain 2.24 (basal diet), 39.03, 85.01, 171.16, 356.49 and 715.46 mg/ kg of vitamin C. The results showed that fish fed on 171.16 mg/kg vitamin C diet had the highest growth performance and feed utilization. Fish fed on the basal diet had higher malondialdehyde (MDA) content and lower activities of antioxidant enzymes in the serum and liver as compared with those fed on vitamin C diets. Polynomial analysis indicated that the optimal dietary vitamin C requirements of juvenile Chu's croaker were 102. 28, 98.21, 150.26, 165.38, 71.46, 176.19, 84.84 and 103.78 mg/kg based on weight gain, specific growth rate, liver storage, muscle storage, liver MDA content, liver alanine aminotransferase activity, liver alkaline phosphatase activity and liver superoxide dismutase activity, respectively. We recommend an inclusion level in the range of 71.46-150.26 mg/kg vitamin C in the diets of juvenile Chu's croaker for optimum growth performance, liver function, antioxidant capacity and innate immunity functions.
K E Y W O R D Santioxidant capacity, Chu's croaker, growth performance, innate immunity, Nibea coibor, vitamin C | 61 ZOU et al.
