Effects of dietary vitamin C on growth and immune response of Japanese seabass, Lateolabrax japonicus

Studies were conducted to investigate the effects of dietary ascorbic acid on growth. survival tissue concentration and immune response of Japanese seabass (initial average weight 6.26 +/- 0.10g). Seven practical diets were formulated to contain 0.0, 12.2. 23.8. 47.6. 89.7. 188.5 and 489.0 mg ascorbic acid equivalent kg(-1) diet, supplied as L-ascorbyl-2-polyphosphate (LAPP). Each diet was fed to triplicate groups of fish in seawater floating cages (1.5 x 1.5 x 2.0 m). and each cage Was stocked with 80 fish. Fish were fed twice daily (06:30 and 16:30) to apparent satiation for 8 weeks. The water temperature fluctuated from 26.5 to 32.5degreesC. salinity from 32parts per thousand to 36parts per thousand and dissolved oxygen approximately 7 mg 1(-1) during the experimental period. The optimum growth was obtained in diets with equal to or more than 47.6 mg ascorbic acid kg(-1) diet. The ascorbic acid concentrations in liver and muscle correlated positively with those in diets. The vitamin C requirements were estimated to be 53.5 mg k(-1) based on growth performance. 93.4 mg kg(-1) based on liver concentration of ascorbic acid and 207.2 mg kg(-1) based on muscle concentration of ascorbic acid. The activities of lysozyme and alternative complement pathway in serum increased with the increase of dietary ascorbic acid. when dietary ascorbic acid reached 489.0 mg kg(-1). these parameters were significantly higher than those of all other treatments. (C) 2004 Elsevier B.V All rights reserved.