| In this study,the optimal requirements of soybean phospholipids in the feed of Chinese mitten crab(Eriocheir sinensis)and juvenile crabs were evaluated from the point of view of survival,growth and digestive enzyme activity,and the possible mechanisms of the beneficial effects of phospholipids on survival,growth and digestion were explored.The results can provide a theoretical basis for optimizing the feed formula of E.sinensis and provide clues for studying the effects of phospholipids(PL)on molting and lipid metabolism.The main results and conclusions of this study are as follows:1 Effects of dietary phospholipid levels on survival,growth,digestive enzyme activity and biochemical index of Eriocheir sinensis: A 50-day feeding experiment was performed to investigate the effects of dietary phospholipid(PL)addition on the survival,growth,digestive enzyme activities,calcium content and neverland(NVD)expression in juvenile Chinese mitten crab(Eriocheir Sinensis).Five experimental diets were formulated with increasing addition of PL(0%,1%,2%,3%,and 4%),which were named PL0,PL1,PL2,PL3 and PL4,respectively.Each diet was randomly assigned to four tanks of juvenile E.sinensis(initial weight: 5.12 ± 0.16g),with eight crabs held in each tank.The results showed that(1)PL addition significantly increased the survival rate(SR),but just slightly increased the weight gain rate(WGR)of juvenile E.sinensis.As the PL addition level increased,SR and WGR first increased and then decreased,with the highest values observed in the PL3 group.(2)As the PL addition level increased,the activities of trypsin and cellulase significantly increased and then decreased,with the highest value observed in the PL2 group and PL3 group,respectively.As PL addition level increased from 1% to 2%,lipase activity increased sharply and then kept constant with further increase of dietary PL.(3)As PL addition level increased from 0% to 3%,the calcium content in the serum significantly increased,and then significantly decreased with further increase of PL addition.PL addition just slightly promoted the calcium content in the hepatopancreas compared with the control group.(4)As PL addition level increased from 0% to 3%,the expression of NVD in the hepatopancreas significantly increased,and then decreased to basal level with further increase of PL addition.In conclusion,2%-3% addition of PL is beneficial for the survival,growth performance,digestive enzyme activities of juvenile E.sinensis.PL addition at a relatively higher level(3%)increased the calcium absorption possibly due to the elevated expression of NVD and its mediated cholesterol metabolism into vitamin D.2 Effects of dietary phospholipid levels on survival,growth,digestive enzyme activity and biochemical index of juvenile E.sinensis: The aim of this study was to study the effects of five phospholipid levels on the survival,growth,digestive enzyme activity and Neverland gene expression of juvenile E.sinensis.In the experiment,palm oil and soybean lecithin were used as the main fat sources to prepare five kinds of diets with equal nitrogen and other lipids.The phospholipid levels were 0%(control group),1%,2%,3% and 4%,respectively,named PL0,PL1,PL2,PL3 and PL4.All kinds of feed were randomly fed to 4 groups of river crabs(initial weight:0.52±0.02g).The experimental period was 60 days.The results showed that(1)Phospholipid addition showed no significant effects on the survival rate of juvenile E.sinensis.The addition of phospholipids significantly increased the weight gain rate and specific growth rate of juvenile crabs,but reduced the feed conversion ratio,with the highest growth rate and lowest feed conversion ratio observed in the PL1 group.(2)The activities of trypsin and amylase in the hepatopancreas of juvenile crabs significantly decreased with the increase of phospholipid level.When the phospholipid level was equal to or above 3%,the activities were significantly lower than that in the PL0,PL1 groups.The amylase activity showed a similar tendency to weight growth rate with the increase of phospholipid level.The amylase activity was highest in the 1% phospholipid group,which was significantly higher than that in PL3,PL4 groups.On the contrary,the lipase activity decreased first and then increased,with the lowest value observed in the PL2 group,which was significantly lower than that in the PL0,PL4 groups.(3)As phospholipid level increased,triglyceride contents in the hepatopancreas of juvenile crabs decreased significantly.When the phospholipid level was equal to or above 3%,the contents were significantly lower than that in the PL0,PL1 groups.(4)As phospholipid level increased to 2%,the expression level of Neverland gene in the hepatopancreas of juvenile crabs significantly increased,and then decreased with further increase of phospholipid level.In conclusion,1% phospholipid significantly promoted growth performance,PL2 increased the expression of Neverland gene in the hepatopancreas,while3%-4% phospholipid decreased the activities of digestive enzymes(trypsin,cellulase and amylase)of crabs.Based on the survival and growth performance,the optimal phospholipids addition level was estimated to be 1% dry diet for juvenile E.sinensis. |
