Effects of dietary selenomethionine levels on growth and some immune indices in juvenile sea cucumber Apostichopus japonicus

Juvenile sea cucumber Apostichopus japonicus with initial body weight of 1.30-1.68 g were stocked into 40 liter plastic tanks at a rate of 15 individuals per tank and fed the diets containing selenomethionine at a rate of 0 mg/kg(control group),0.2 mg/kg(group A),0.4 mg/kg(group B),0.6 mg /kg(group C),0.8 mg/kg(group D) and 1.0 mg/kg(group E) with triplication at water temperature of 14.0-8.0 ℃,a salinity of 30-32,and pH 7.5 for 60 days.Some growth indices and enzyme indices of the sea cucumber were measured after the experimental animals were starved for 24 hours at the end of the experiment.The results showed that there was no significant difference in survival of the sea cucumber in the experiment(P0.05).The SGR,the crude protein content in dry mater in body walls,and protein apparent digestibility(%) were also significantly higher in the sea cucumber fed the diets containing 0.6 mg/kg selenomethionine than those in the control(P0.05),while the poor SGR was observed in the sea cucumber fed the diets containing 1.0 mg/kg selenomethionine.The maximal selenium level was found in the intestine of the sea cucumber fed the diets containing 0.6 mg/kg selenomethionine,but was observed in the body wall of the sea cucumber fed the diets containing 0.4 mg/kg selenomethionine,significantly higher than that in the control group(P0.05).The sea cucumbers fed the diets with 0.6 mg/kg selenomethionine had the maximal SOD activity.However,the maximal CAT and ACP activities were found in the coelomic fluid of the sea cucumber fed the diets containing 0.4 mg/kg selenomethionine,significantly than those in the control group.It is suggested that the optimum dietary selenomethionine supplementation should be 0.4-0.6 mg/kg in order to increase the growth performance and immunity in the sea cucumber.