Preliminary Study of the Dietary α-Tocopherol Requirement in Sea Cucumber, Apostichopus japonicus

This study was conducted to evaluate the dietary alpha-tocopherol (vitamin E) requirement in juvenile sea cucumber, Apostichopus japonicus. Sea cucumbers averaging 1.48 +/- 0.07 g (mean +/- SD) were randomly distributed into 18 rectangular plastic tanks of 20 L capacity in a recirculating system (20 animals per tank). Six semi-purified experimental diets with average protein and crude lipid levels (dry matter) of 29.7 +/- 0.36% and 4.39 +/- 0.23% (mean +/- SD), respectively were formulated to contain 0 (E4), 15 (E12), 30 (E23), 60 (E44), 120 (E77) and 600 (E378) mg alpha-tocopherol/kg diet, supplied as dl-alpha-tocopheryl acetate. Diets were analyzed for alpha-tocopherol content by HPLC and the alpha-tocopherol levels were 4.01, 12.4, 23.1, 44.3, 77.4 and 378 mg alpha-tocopherol/kg diet for E4, E12, E23, E44, E77 and E378 diets, respectively. Casein and defatted fish meal were used as the protein sources in the diets while wheat flour was the carbohydrate source. Sea cucumbers were fed each of the six experimental diets in triplicate groups. At the end of the 14-week feeding trial, weight gain (WG), specific growth rate (SGR) and feed efficiency (FE) of sea cucumbers fed on E23, E44, E77 and E378 diets were significantly (P < 0.05) higher than those of animals fed on E4 and E12 diets. However, there were no significant differences in WG, SGR and FE among sea cucumbers fed on E23, E44, E77 and E378 diets or among those fed on E4 and E12 diets. Survival of sea cucumbers fed on E44, E77 and E378 diets were significantly higher than those of animals fed on E4, E12 and E23 diets. However, there were no significant differences among sea cucumbers fed on E4, E12 and E23 diets or among those fed on E44 and E77 diets. Whole-body vitamin E concentration increased with alpha-tocopherol content of the diets. Broken line analysis of WG showed an optimum dietary alpha-tocopherol requirement of 41 mg alpha-tocopherol/kg diet in sea cucumber. These results indicated that the optimum dietary alpha-tocopherol requirement in sea cucumber in the form of dl-alpha-tocopheryl acetate could be higher than 23.1 mg alpha-tocopherol/kg diet but lower than 44 mg alpha-tocopherol/kg diet.