Effects Of Vitamin E On Growth And Immunity Of Sea Cucumber(Apostichopus Japonicus) Under Environmental Stresses

Sea cucumber (Apostichopus japonicus) is one of the most important commercial mariculture species in Northern China, the hatchery-reared juveniles of which are usually held in indoor facilities. In this period, intensive culture and excessive feeding may lead to a deterioration of aquaculture water quality, which may negatively affect on growth rate and health of sea cucumber. Currently, antibiotics were used to prevent diseases of sea cucumber. However, the use of antibiotics may cause problems in food safety. Therefore, how to improve disease resistance of sea cucumber without using antibiotics has become an urgent issue in sea cucumber culture. The aim of this study was to provide a feasible way to solve the problem in sea cucumber culture. The present study investigated the requirement of sea cucumber on vitamin E, and the effects of vitamin E on the growth and immunity of sea cucumber under environmental stresses. In addition the mechanism of vitamin E action on growth and immunity of sea cucumber was explored.The main findings in this study are listed as follows:(1) The requirement of sea cucumber on vitamin E was investigated through analysising contents of vitamin E in body wall, intestinal tissue and intestinal digesta of sea cucumber. The effects of major environmental factors in intensive culture of sea cucumber were also investigated. The results showed that the contents of vitamin E in body wall, intestinal tissue and intestinal digesta were6.3,7.2and6.1mg kg-1respectively. The results indicated that vitamin E was necessary for sea cucumber and the main impact environmental factors were ammonia and nitrite in sea cucumber culture.(2) The feeding trial was conducted to determine the dietary vitamin E requirement and its effect on the growth and immunity of juvenile sea cucumber. The results showed that dietary vitamin E could increase the specific growth rate (SGR), survival rate, non-specific immunity, disease resistance and antioxidant capacity of sea cucumber. The results indicated that a level of88-92mg kg-1vitamin E was required for maximal growth and non-specific immune responses of sea cucumber.(3) The feeding trials were conducted to study the effects of vitamin E on growth and immunity of sea cucumber under stresses induced by ammonia and nitrite. The results showed that the specific growth rate (SGR), survival rate, non-specific immunity and disease resistance were reduced, at same time, the lipid peroxidation in body wall and mortality of sea cucumbers induced by vibro splendidus challenge were all increased. Dietary vitamin E supplementation in diet resulted in increased in specific growth rate (SGR), survival rate, the activity of acid phosphatase (ACP) and superoxide dismutase (SOD) in compared to the control. The vitamin E supplemented diet could reduce the lipid peroxidation in body wall and mortality of vibro splendidus challenge, and dietary vitamin E requirement of sea cucumber for maximum of growth and non-specific immune responses was200mg kg-1under stresses induced by medium ammonia and nitrite. The results demonstrated that chronic ammonia and nitrite caused negative effects on growth and immunity, and increased the dietary vitamin E requirement of sea cucumber. The supplement vitamin E in diets could diminish the effects of oxidative stress such as oxidative damage of tissues and energy consumption, and maintained the function of the immune system of sea cucumber. Therefore, vitamin E could reduce toxicity of ammonia and nitrite.(4) The feeding trials were conducted to study the mechanism of vitamin E on the growth and immunity of sea cucumber. The results showed that the supplementary vitamin E in diets increased the intestine folds height of sea cucumber and the activity of intestinal protease, lipase and alginase. The lipopolysaccharide induced experiments showed that vitamin E could reduce the levels of nitric oxide and prostaglandin analogues in sea cucumber, and inhibited the activity of nitric oxide synthase (NOS). The results demonstrated that vitamin E promoted the growth by influencing of intestinal digestive enzymes and intestinal structure of sea cucumber. Vitamin. E could affect the immunity of sea cucumber via prostaglandin and nitric oxide pathway, in which the antioxidation of vitamin E plays an important role.