Study On Application And Mechanism Of Phospholipids Supplemented In Microdiets Of Pelteobagrus Fulvidraco Larvae

Phospholipid(PL) is a bioactive compound,has a broad application prospect because of its unique physico-chemical property and nutritional value.Dietary PL supplementation has potential importance for the formulation of practical larval diets,but the origin of the requirement is still unclear.The study was conducted to investigate the effects of PL supplementation in formulated microdiets on growth,survival,stress resistance,lipid metabolism,antioxygen ability and foregut and liver histological changes of Pelteobagrus fulvidraco larvae.This investigation was aimed to reveal the mechanisms of the PL requirement from macroscopic and microcosmic aspects,which can provide information on the practical use of PL in larval microdiets.1 Changes in lipids and fatty acid composition during development in Pelteobagrus fulvidraco fertilized eggs and larvaePurpose:To establish the changes which during embryogenesis and early larval development,fertilized eggs and larvae of Pe#eobagrus fulvidraco were examined for lipids and fatty acid compositions.Method:The lipids content and fatty acid composition in the fertilized eggs and larvae which did not feed for 7 days after hatching were analyzed by means of common chemical assay and gas chromatography(GC).Result: The lipid content of fertilized eggs tended to increase during hatching period,while the PL content increased a little from 16h after fertilization.Fertilized eggs contained more polyunsaturated fatty acids(PUFA) and monounsaturated fatty acids(MUFA) than saturated fatty acids(SFA).There was no significant change in the proximate fatty acid composition of eggs during hatching.The lipid and PL content of larvae decreased sharply after hatching.Total lipid decreased from 4.57%on day 0 to 0.75%on day 7 and PL content decreased from 1.32%to 0.14%.A further analysis showed that the reduction in lipid content of larvae was significantly larger than in the PL content from day 0 to day 5.The fatty acid composition in starved larvae changed significantly as starvation progressed.In starved larvae the MUFA content decreased significantly and the greatest decrease occurred in the C18:1 content.In this regard the degree of decreases was,n-9＞n- 6＞n-3,suggesting that MUFA were a major energy source for starving Pelteobagrus fulvidraco larvae,DHA and AA were conserved in preference to EPA.Conclusion:PL is a necessary nutrient for normal growth and development of larvae which served as an important energy source for metabolism during larval period.The larval fish have a huge PL requirement.2 Effect of phospholipid supplementation in formulated microdiets on growth,survival and stress resistance of Pelteobagrus fulvidraco larvaePurpose:The effect of supplementation of soybean PL to Pelteobagrus fulvidraco larvae diets on growth survival and stress resistance were investigated.Method:All Pelteobagrus fulvidraco larvae obtained following artificial fertilization were randomly divided into 5 groups with 4 replicates of 10000 larvae each.The larvae were fed from day 3 to 21 posthatch with four diets containing the same basal diet,coated with different lipid fractions(6%diet).The lipid fractions consisted of increasing levels of soybean PL (0,2,4 or 6%of diet) and decreasing levels of mixed oil(fish oil:soybean oil,2:1).A group of larvae was fed rotifers as a control.The growth performance,survival rate and stress resistance ability were determined after the experiment.Results:the PL content of microdiets significantly influenced the performance of larvae(p＜0.05).The body weight and total length of larvae increased as a result of PL supplementation.Larvae fed diet supplemented with 6%PL exhibited the best growth performance and similar to those fed rotifers.The condition factor of larvae was not significantly affected by dietary PL level on day 14 and day 21(p＞0.05).Survival was high and above 90%at the end of the feeding trial in all groups and did not differ significantly among the groups,except for group PL0.Survival of fish fed the diet with no supplementation of PL was lower than the other groups and tended to increase with increasing dietary PL levels.Larvae fed PL6 diet and rotifers had significantly higher average daily gain(ADG),length gain rate(LGR), weight gain rate(WGR) and specific growth rate(SGR) than those fed the other diets (p＜0.05) and larvae fed PL0 diet was the lowest(p＜0.05) during days 0-7.The ADG of larvae in each group during days 14-21 was higher than that during 0-7days.The larvae in group PL6 still had the highest ADG,while the ADG of larvae fed rotifers increased little during days 14-21.The LGR,WGR and SGR of larvae in each group were lower during days 14-21 than those during days 7-14 and those of the larvae in control group fed rotifers decreased significantly.The WGR and SGR of larvae in group PL0 were significantly higher than those in the other groups(p＜0.05).During the whole test period, the ADG,LGR,WGR and SGR of larvae all increased with increasing dietary PL levels. The length-weight relation of Pelteobagrus fulvidraco larvae was consistent with the general growth model of fish.The index b of length-weight relation equation varied from 2.62 to 2.77.The feed coefficient(FC) of larvae tended to decreased with the increasing dietary PL levels.The stress resistance ability of larvae appears to be less affected by the dietary PL supply.Conclusion:PL had a growth-promoting effect on Pelteobagrus fulvidraco larvae,improved feed efficiency and enhanced survive rate.3 Effect of phospholipid supplementation in formulated microdiets on lipids and fatty acid composition of Pelteobagrus fulvidraco larvaePurpose:This study was undertaken to assess the effect of different lipid sources and dietary PL supplementation on lipid metabolism especially fatty acid composition of Pelteobagrus fulvidraco larvae and further investigated the mechanism of the growth-promoting effect of PL.Method:According to the design of part 2 above,the lipids content and fatty acid compositions in whole body of larval fish in each treatment were analyzed after feeding.Results:Dietary fatty acid loss or gain did not change significantly after the stability test.The fatty acid compositions of microdiets leached into the water during the stability test was not affected by dietary PL supplementation.The total lipid content of larvae tended to increased as a result of PL supplementation and the fish aged.The total lipid contents of group PL4 and PL6 were significantly higher than that of group PL0 and PL2(p＜0.05) and group PL6 was highest on day 21,though the difference was not significant from the other groups(p＞0.05).The PL content of larvae was affected by dietary PL on day 14.The difference of PL content among group PL4, PL6 and control group fed rotifers was not significant(p＞0.05) and significantly higher than that in group PL0(p＜0.05).The PL content of larvae did not differ significantly among the groups on day 21(p＞0.05).Compared with day 14,the increase of PL content in group PL0 was significantly higher than that in the other groups on day 21(p＜0.05). On day 14,the contents of C18:2n6c,C18:3n6,C18:3n3,PUFA and n-6PUFA showed significant difference(p＜0.05) and increased with increasing the dietary PL levels.The contents of DHA and EPA in group PL6 were significantly higher than those in group PL0 (p＜0.05).The contents of C18:0 and SFA decreased significantly as a result of PL supplementation.On day 21,C18:2n6c,PUFA and n-6PUFA contents of larvae fed the diets with supplementation PL were increased significantly,while the 16:0 and SFA contents decreased.Comparison of fatty compositions of larvae at different ages of each group,the contents of C18:2n6c,C18:3n3,EPA,DHA,PUFA and n-3PUFA increased, while C 16:0,C20:4n6 and SFA decreased as the fish aged.The contents of C 16:0,C 18:0, EPA and SFA in control group fed rotifers were higher than those in groups fed microdiets,and C18:2n6c,DHA and PUFA were lower.The fatty acid compositions of larvae fed rotifers were characterized by the specific fatty acids related to the rotifer. Conclusion:The supplementation of PL to the diet could increased lipid retention in larval fish and enhanced the absorption and utilization of dietary EFA.4 Effect of phospholipid supplementation in formulated mierodiets on antioxygen ability and ATPase activity of Pelteobagrus fulvidraco larvaePurpose:This study was undertaken to assess the effect of dietary PL supplementation on antioxygen ability and ATPase activity of Pelteobagrus fulvidraco larvae and further investigated the mechanism of the growth-promoting effect of PL. Method:According to the design of part 2 above,antioxygen ability and ATPase activity of larval fish in each treatment were analyzed after feeding.Results:The content of MDA in larvae decreased and SOD,CAT and GST activities increased with increasing the dietary PL levels.The GSH-PX activity of larvae fed the diets with supplementation PL were higher than the PL0 group(p＜0.05).The GSH-PX activity was the highest in the group fed 4%PL and did not improved by the addition of 6%PL.The SOD,CAT,GST and GSH-PX activities of larvae increased while the content of MDA decreased on day 21 compared with day 14.The addition of PL improved Na⁺,K⁺-ATPase and Ca²⁺-ATPase activities of larvae.The Na⁺,K⁺-ATPase and Ca²⁺-ATPase activities of larvae fed the diets with supplementation PL were significantly higher than the PL0 group fed the diet with no supplementation PL on day 14 and day 21(p＜0.05).The ATPase activity of group PL4 was the highest and group PL0 was the lowest.Comparison of ATPase activities of larvae at different ages of each group,The Na⁺,K⁺-ATPase and Ca²⁺-ATPase activities of larvae fed microdiets decreased a little on day 21 compared with day 14.Conclusion:PL could maintain cellular membrane integrity,induce the oxidative damage to biomembrane by free radicle and improve antioxygen ability and ATPase activity of larval fish.5 Effect of phospholipid supplementation in formulated microdiets on foregut and liver histological changes of Pelteobagrus fulvidraco larvaePurpose:This study was undertaken to determine the effect of commercial PL supplementation in formulated microdiets on foregut and liver histological changes of Pelteobagrus fulvidraco larvae,which can further investigated the mechanism of the growth-promoting effect of PL with the study of histology and digestive physicalogy. Method:According to the design of part 2 above,Larvae were sampled from each group on days 14 and 21 for make tissue sections.The tissue sections were observed and analyzed by histological image system and light microscopy.Results:On day 14,larvae fed PL0 diet showed steatosis in the intestinal mucosa with a high incidence of lipid vacuoles and the hepatic tissue was in disorder with blurred hepatic trabecula,swollen hepatocytes contained numerous lipid cacuoles.The degree of lipid accumulation decreased and the number of goblet cells increased in the enterocytes of the anterior intestine with decreasing dietary oil supplementation level and with increasing PL supplementation.The enterocytes and hepatic tissue of larvae fed PL6 diet showed normal morphology,which similar to those fed rotifers.The degree of lipid accumulation in the anterior intestine and in the liver on day 21 was lower than that on day 14.The number of vacuoles in the anterior intestine decreased while goblet cells appeared more numerous.A considerable reduction of the vacuolization was also observed in the liver of fish fed the different experimental diets.Conclusion:The addition of PL to the diet caused a reduction in the degree of lipid accumulation,enhancing lipid transport and promoting the maturation of the digestive organs of larvae.As the fish aged,the ability of PL synthesis was enhanced and the effect of PL decreased,thus the PL requirement of fish decreased with age or development stage.