Application Of Surfactin In Diet Of Growth Retarded Marbled Eels(Anguilla Marmorata) At Elver Stage

This trial was conducted to investigate surfactin application in the diet of growth retarded marbled eels(Anguilla marmorata)at elver stage.Six hundred and forty marbled eels at elver stage were randomly divided into four treatments with four replicates in each group and 40 fish in each replicate.The dietary surfactin levels of the four treatment groups were 0(control group),25,50,and 100 mg/kg,respectively.The trial period was 10 weeks.Compared with control group,the finial body weight,weight gain rate and survival rate of surfactin supplementation groups were significantly improved(P<0.05),and those parameters in25mg/kg surfactin supplementation group were significantly higher than those of other surfactin groups.Feed conversion rate,relief rate and survival rate were improved significantly(P<0.05),and no significant differences of those parameters were found among surfactin supplemented groups(P>0.05).Amylase activities and lipase activities(except 25 mg/kg surfactin supplementation group)in all groups were similar(P>0.05);protease activities of in intestine of surfactin supplementation groups were significantly higher than those of control group(P<0.05),and protease activity of 25 mg/kg surfactin supplementation group were significantly higher than those of other two surfactin supplementation groups(P<0.05).The glutamic-oxalacetic transaminase activity,glutamic-pyruvic transaminase activity and Triglyceride levels in liver of fish fed diets with surfactin supplementation were similar(P>0.05);total cholesterol levels of three groups with surfactin supplementation were lowered significantly(P<0.05),and no significant differences were found among all three surfactin supplementation groups(P>0.05).Fish fed diets with surfactin supplementation had greater height of mucosa fold(P<0.05),no significant differences in surfactin supplemented groups(P>0.05).Adequate surfactin supplementation in diets of fish decreased the E.coli population significantly(P<0.05),increased the Lactobacillus population significantly(P<0.05),and had no effect on total bacterial population in intestine of growth retarded marbled eels(P>0.05).Total antioxidation capacity level and activities of superoxide dismutase in intestine of fish fed diets with surfactin supplementation were significantly increased(P<0.05),those two parameters in 25 mg/kg surfactin group were significantly higher than those of other two surfactin groups(P<0.05).The activities of glutathione peroxidase were increased by surfactin supplementation(P<0.05),andno significant differences were found among all three surfactin supplementation groups(P>0.05).The activities of catalase were not affected by surfactin supplementation(P>0.05).The Malondialdehyde levels and reactive oxygen species levels of fish fed diets with surfactin supplementation were significantly lowered(P<0.05),and no significant differences were found among three surfactin supplementation groups(P>0.05).In conclusion,25 mg/kg surfactin supplementation in diet of growth retarded marbled eels at elver stage could effectively improve the growth performance and intestinal health status.