Effects of Dietary La~(3+) on Growth,Immunity and Disease Resistance to Vibrio splendidus of Sea Cucumber,Apostichopus japonicas

A 8-week feeding experiment was conducted to evaluate the effects of La3+on the sea cucumber(initial average weight(6.72±0.01)g).Five practical diets were formulated with graded level of La3+(0,10,25,50 and 75mg/kg dry feed).At the end of the feeding experiment,sea cucumbers were weighed by tank to monitor growth.Four sea cucumbers were randomly collected for the assay of immune parameters.The remaining juveniles were injected with the pathogen bacteria V.Splendidus and monitor the accumulative mortality rate during 14 d.The experiment result indicated that the specific growth rate of 50mg/kg La3+group was 36.92% higher than the control group.Compare to the control,sea cucumbers fed with 50mg/kg La3+had significant higher activities of phagocytosis,respiratory burst,acid phosphatase(ACP)andalkaline phosphatase(AKP).The activity of total superoxide dismutase(T-SOD)and total nitric oxide synthase(T-NOS)of coelomocytes was tending to increase as dietary La3+increased from 10 to 50mg/kg,but there were no significant differences.The result of challenge test also showed that sea cucumbers fed with 50mg/kg La3+had significantly lower accumulative mortality compared with the control groups.In conclusion,the oral administration of La3+on the sea cucumber at a dose of 50mg/kg can improve growth,enhance the immunity as well as increase disease resistance.