Effect Of Dietary Lipid And Vitamin E On Growth And Immune Response Of Juvenile Chinese Mitten Crab Eriocheir Sinensis

In this study, experiment technology like animal nutrition, physiology, biochemistry and molecular biology, are used to explore the lipid nutrition physiology of Chinese mitten crab (Eriocheir sinensis). These included requirement of cholesterol and the interaction between dietary cholesterol and phospholipids; the effects of dietary lipid sources and its combination on the growth, antioxidant ability and immune response of crab; effects of dietary lipid sources with supplements of vitamin E on the growth, antioxidant ability and disease resistance of crab. Two immune related genes including FABP (Fatty acid binding protein) and ACBP (Acyl-CoA-binding protein) were cloned and evaluated how their expressions were regulated by dietary lipid. The main results can be briefly summarized as follows:1. The requirement for cholesterol of juvenile Chinese mitten crab at different phospholipids levelsCholesterol and dietary phospholipids are important to the growth and survival of crabs. Phospholipids enhance cholesterol solubilization while phosphatidylcholine transfers cholesterol from the hepatopancreas to the hemolymph. Diets containing six levels of cholesterol and two levels of phospholipids (1%and2%) were conducted to evaluate the growth performance, body composition of juvenile Chinese mitten crab. Crabs (2.3±0.05g) were randomly assigned to48tanks (300L) with four replicates each treatment. After42-day feeding trial, no significant differences were observed in survival, crab fed diet containing1%phospholipids and0.5%cholesterol showed higher weigh gain and specific growth rate than other groups, while resulted lowest feed coefficient. By two-way ANOVA analysis, there was interaction between dietary phospholipids and cholesterol no the weight gain, specific growth rate, crude lipid and the accumulation of cholesterol in the hepatopancreas of juvenile Chinese mitten crab, no interaction was observed on survival, molting rate and other body composition. After linear regression analysis using quadratic according the weight gain, the optimal cholesterol level in the diet were0.62%and0.23%separately at1%and2%phospholipids levels.2. Growth and immune response of Chinese mitten crab (Eriocheir sinensis) fed diets containing different lipid sourcesSix isonitrogenous and isoenergetic diets were formulated with fish oil (FO), linseed oil (LO), soybean oil (SO), rapeseed oil (RO), coconut oil (CO), and beef tallow oil (BTO) as lipid sources with five replicates each. Thirty crabs (2.35±0.14) g were stocked into each tank (300L) and fed twice daily. After10-week feeding trial, growth and immune responses were evaluated. No significant differences were observed in survival in all the treatments. Weight gain and specific growth rate of crab fed the FO diet were significantly lower than in other groups. Crab fed the SO diet weighed more than those fed any other diets. Crab in the FO group had the highest activities of acid phosphatase and alkaline phosphatase. Activity of serum superoxide dismutase of crab fed the SO diet were significantly lower than those in the FO and LO groups. Serum malondialdehyde content of crab fed FO diet was highest among all the groups. Serum PO and LYZ activities were highest in FO group while BTO was lowest, all the groups followed the trend FO>SO>CO>RO>LO>BTO in PO activity and FO>SO>CO>LO>RO>BTO in LYZ activity. FABP expression in the hepatopancreas of SO group was significantly higher than all the other groups, expression of FO, LO and RO were higher than that in the CO and BTO group. ACBP expression in the hepatopancreas of CO and BTO group were also significantly lower than other groups, yet no significant differences were observed between FO, LO, SO and RO groups. Our results indicated that the use of dietary vegetable or animal oils can achieve similar growth performance to fish oil in juvenile Chinese mitten crab, but non-fish oils may impair crab immunity. Soybean oil is recommended as a suitable replacer for fish oil in Chinese mitten crab diet.3. Effect of replacing dietary fish oil with soybean oil on growth, nonspecific immune response, and disease resistance ability in Chinese mitten crab, Eriocheir sinensisFive isonitrogenous and isoenergetic diets with fish oil replacing by soybean oil0%(control),25%,50%,75%and100%(F1-F5) were formulated, and randomly assigned to juvenile crabs (0.27±0.03g) with four replicates each treatment for42days. The effects on growth performance, non-specific immune response and anti-disease ability of juvenile E. sinensis were evaluated. After42-day feeding trial, the results showed that there was no significant difference in the survival rate among the treatments (P>0.05). The weight gain was significantly higher in the F4group than in the F1group (P<0.05). Similarly, the crabs in the F4group had significantly higher serum ACP (acid phosphatase), AKP (alkaline phosphatase), and serum SOD (superoxide dismutase) activities than the other treatment groups (P<0.05). F4and F3group were significantly higher than the other groups (P<0.05). Serum MDA (malondialdehyde) content was significantly higher in the Fl group than in the other groups, but there was no difference between the other groups (P>0.05). Serum PO (phenoloxidase) activity was the higher in F4and lower in F5than the other groups (P<0.05). There was no difference in serum LYZ (lysozyme) activity among the groups (P>0.05). After the feeding experiment, the crabs were infected with Aeromonas hydrophila for10d. The first death was recorded in F5, and the crabs in F5had significantly higher cumulative mortality than in F1and F4(P<0.05), but there was no significant difference between the other groups (P>0.05). FABP expression in the hepatopancreas of F4group was highest among all the groups, ACBP expression in the hepatopancreas of F3and F4groups were higher than other groups. In conclusion, the results suggests that replacing fish oil by soybean oil might not influence the survival and growth of juvenile E. sinensis, yet anti-disease ability would be suppressed. Thus, replacing75%of fish oil by soybean oil can improve the growth while not reducing its anti-disease ability, which is recommended in diet formulation for juvenile E. sinensis.4. Growth and non-specific immune responses in Chinese mitten crab (Eriocheir sinensis) fed two levels of vitamin E along with three lipid sourcesThe experiment evaluated the effects of different lipid sources on the growth and immune response of juvenile Chinese mitten crab at two VE levels (100mg/kg and300mg/kg diet). Fish oil (FO), linseed oil (LO) and soybean oil (SO) were selected. Six isonitrogenous and isoenergetic diets including100FO,100LO,100SO,300FO,300LO and300SO were randomly assigned to crabs (0.27±0.01) with four replicates each treatment. After42-day feeding trial, the results show that no significant differences were observed between all the groups, growth and specific growth rate of300FO group was significantly higher than other groups. No differences were found between all the treatments on body composition including protein, lipid, moisture and ash. Result from the fatty acid analysis of hepatopancreas indicated that crab of300FO had highest n-3HUFA among all the groups, followed by100FO,300LO and100LO, crab fed100SO and300SO diets were lowest. Serum SOD (superoxide dismutase) activities in crab of100FO and100LO resulted significantly higher than other groups while100FO was highest.100FO also had highest serum MDA (malondialdehyde) content. FO group in the two VE levels both showed highest PO activity, and significantly higher than the other groups (P<0.05). When supplement VE in LO and SO groups, PO activity were higher than their treatment at a lower level of VE groups. No significant differences were found in the serum LYZ (lysozyme) activity between all the groups. After the feeding experiment, the crabs were infected with Aeromonas hydrophila for10d. The crabs in the300SO group had significantly higher cumulative mortality than those in the100FO,100LO and300FO groups. In conclusion, higher VE can protect fish oil in the diet and had positive effect on the growth performance, immune function and disease resistance ability of juvenile Chinese mitten crab.