Effects Of Silymarin On Growth Performance And Lipid Utilization Of Juvenile Chinese Mitten Crab Eriocheir Sinensis

In aquaculture practice,high lipid contents and over-oxidized oils of dietary have brought many negative effects to aquatic animals.Silymarin is a kind of flavonoid complexes with various pharmacological activities,which is extracted from the dried fruit of Silybum marianum L.Gaertnn.Studies on mammals and fish have shown that silymarin has the effects on protecting liver,regulating lipid metabolism and alleviating lipid peroxidate damage.However,the study about silymarin on the efficient utilization of dietary lipid in crustaceans has not been reported yet.In this research,cultivation experiments were conducted in order to evaluate the effects of silymarin on the growth performance and lipid utilization of juvenile Chinese mitten crab Eriocheir sinensis in diets containing different lipid levels and oxidized fish oil and determine the appropriate silymarin supplement under normal lipid level.The results of this study can provide theoretical basis for future application of silymarin in dietary of crustacean.Findings and conclusions are as follows: 1.Effects of dietary lipid contents and silymarin on growth performance and lipid metabolism in E.sinensisThe effects of silymarin supplementation in the diet on growth performance and lipid metabolism of E.sinensis at two dietary lipid levels(7% and 13%)were evaluated.A total of six isonitrogenous diets were formulated with 0,100 and 300 mg/kg silymarin supplementation to each diet with different dietary lipid contents,and fed to E.sinensis(2.45 ± 0.01 g)for 8 weeks.The results revealed that both weight gain and specific growth rate of crabs were significantly increased with the increasing of dietary silymarin supplementation contents regardless of dietary lipid levels(P < 0.01).The activities of LPS and LPL in the hepatopancreas of crabs were also significantly enhanced by dietary silymarin supplementation(P < 0.05).The results of real-time PCR analysis revealed that dietary silymarin supplementation significantly increased mRNA expressions of TGL,CPT-l and IL regardless of lipid levels(P < 0.05).Meanwhile,silymarin supplementation significantly increased the activites of SOD and GSH-PX and decreased the content of MDA(P < 0.05).The research showed that silymarin supplementation in dietary can not only improve the growth performance,but also promote the catabolism and utilization of lipid by E.sinensis,and can also enhance the antioxidant capacity in the hepatopancreas of crabs.2.Effects of dietary silymarin levels on growth performance,body composition and antioxidant ability of E.sinensis.Eight experimental diets were formulated with basal diets added of silymarin of 0,50,100,200,300,400,800 and 1600 mg/kg(SM0,SM50,SM100,SM200,SM300,SM400,SM800 and SM1600).Each experimental diets were fed to E.sinensis(2.45 ± 0.01 g)for 8 weeks.The results indicated that the weight gain and specific growth rate were firstly increased and then decreased with the increase of dietary silymarin supplementation and the highest values were all found in crabs fed diet with silymarin supplementation of 300 mg/kg,which were significantly higher than that in SM0 group(P < 0.05).There was also no significant difference in the feed conversion ratio and survival among all treatments(P > 0.05).Contrasted with SM0,there was no significant difference in the contents of crude lipid,crude protein,monisture and ash among all groups(P > 0.05).The activites of GSH-PX in hepatopancreas among all treatments have no significant difference compared to SM0(P > 0.05),and the highest value was found in SM300.Compared with SM0,activities of SOD in hepatopancreas of crabs among other treatments were higher,but without significant difference(P > 0.05).The contents of MDA in the hepatopancreas of crabs in all treatments were lower than content of crab in SM0,but no significant difference was found(P > 0.05).Specific growth rate was regard as criterion,based on broken-line regress model analysis,the optimal supplementation of silymarin is 264.9 mg/kg.Therefore,according to the the growth performance and antioxidant capacity of E.sinensis,it is suggested that the appropriate silymarin supplemental level in the dietary of E.sinensis)is 264.9-300 mg/kg.3.Effect of oxidized fish oil and silymarin addition on growth performance,antioxidant capacity and non-specific immunity of E.sinensisThe effects of silymarin supplementation in the diet on growth performance,antioxidant ability and non-specific immunity of E.sinensis at four oxidized fish oil levels(0,70,140 and 210 mg/kg)were evaluated.A total of eight basal diets were formulated with 0 and 300 mg/kg silymarin to each oxidized fish oil diet,and fed to E.sinenses(1.022 ± 0.001 g)for 7 weeks.The results indicated that both weight gain and specific growth rate of crabs were significantly decreased with the increase of the degree of oxidation of fish oil in diets(P < 0.05).Compared with SM0,weight gain and specific growth rate of crabs were increased in SM300 group,and the difference in F group was significant(P < 0.05).Besides,the contents of ash,crude lipid and crude protein of crabs were also increased with the increasing of dietary silymarin supplementation,and the difference in F group was also significant(P < 0.05).The activities of SOD and GSH-PX in SM300 group were higher than those in SM0 and the contents of MDA in SM300 were lower than that in SM0 group,but all had no significant difference(P > 0.05).With the increase of oxidation degree of fish oil in diets,the activities of AKP in hepatopancreas of crabs were significantly decreased(P < 0.05),the activities of ACP was also decreased,but had no significant differences(P > 0.05).The effects of silymarin on the activities of AKP and ACP in hepatopancreas of crabs were not significant(P > 0.05).The results suggested that excessive oxidation of fish oil had significantly negative effects on the growth performance,antioxidant activity and nonspecific immunity of E.sinenses.Adding 300 mg/kg silymarin to the diet with oxidized fish oil is beneficial to the accumulation of nutrients and improve the growth performance of crabs.However,the effects of alleviating oxidative damage caused by oxidized fish oil and improving non-specific immunity of crabs is not significant.Therefore,it is suggested that the supplement of silymarin in oxidized fish oil feed should be increased.