| As one of the necessary important nutrients for animal,oil has been widely used in feed.Oil in the process of fish growth,development and reproduction has important physiological functions,but oxidized oil can cause damage to animals,influence the growth of animals and physical performance.Bile acid is one of the sterol compounds synthesized from cholesterol,plays an important role in the digestion and absorption process of lipid.As a feed additive,bile acid is also widely used in livestock poultry or aquaculture.For this study,allogyogenetics silver crucian carp is the object,then,we design 8 groups: Fresh oil group,group F,4% soybean oil;Oxidized oil group,O group,4% soybean oil oxide;group BA1 and group BA2(adding 0.03% and 0.06% bile acid compounds in group F,respectively);group BO1 and group BO2(adding 0.03% and 0.06% bile acid compounds in group O,respectively);group U1 and group U2(adding 0.02% and 0.04% ursodeoxycholic acid in group F,respectively).By 3 experiments,we analysed growth performance,antioxidant capacity,serum biochemical indexes,gallbladder bile acid composition,the expression of related genes of endogenous metabolism of bile acid cholesterol,for investigating whether bile acid supplementation in diets modulates to reverse the adverse effects and improve bile acid metabolism for induced by the oxidized oil in fish.At the same time,we charged allogynogenetic silver crucian carp with virus(Cy HV-2)by injection,through the analysis of immune protection,blood immunological index,serum bile acid content,explore the bile acid supplementation in diets for immune protection to allogynogenetic silver crucian carp infected by Cy HV-2.Experiment 1: after breeding ecperiment,by analysised growth performance,serum antioxidant index,serum biochemical indexes of allogynogenetic silver crucian carp,the results showed:(1)the specific growth rate(SGR)of group BA2 was 1.07% / d,feed coefficient(FCR)was 2.02,and had no significant difference with group F(P > 0.05),but the fish body protein deposition rate significantly increased(P < 0.05);the growth performance of fish in BA1,U1 and U2 was significantly lower than that in group F(P < 0.05);compared with group O,BO1 and BO2 significantly improved the growth performance of crucian carp(P < 0.05).(2)BA1 and BA2 group serum superoxide dismutase(SOD)and catalase(CAT)activity increased significantly with the F group(P < 0.05),BA2 group serum total antioxidant capacity(T-AOC)compared with group F had no significant difference(P > 0.05);compared with group O,T-AOC in BO2 group decreased significantly(P < 0.05),and SOD and CAT activity showed no significant difference(P>0.05).There was no significant difference in SOD activity between U2 group and F group,and CAT activity of U2 was significantly higher than F group.MDA content of O group was significantly higher than all the other groups(P < 0.05).(3)The two kinds of diets adding bile acid compounds were significantly reduced the crucian carp serum alanine aminotransferase(ALT)and aspertate aminotransferase(AST)activity(P < 0.05).The ALT activity of U1 was significantly lower than that of group F(P < 0.05),while U2 group showed no significant difference with group F(P < 0.05),and the AST of the two groups was significantly lower than F group(P < 0.05).(4)After adding bile acid,compared with the group O and F respectively,serum cholesterol(TC)content were significantly decreased(P < 0.05)and triglyceride(TG),though there was no significant difference(P > 0.05),but have a certain degree of decline.There was no significant difference in the content of high-density lipoprotein(HDL)and low-density lipoprotein(LDL)in the serum of the carp(P > 0.05)Experiment 2: Further tested the experiment 1,F,O,BA2 and BO2 group serum,liver and intestinal bile acid,cholesterol,and by high performance liquid chromatography(HPLC)method to analysis the gallbladder bile acid composition of bile,liver and intestinal bile acid cholesterol metabolism related gene expression were analyzed by using real-time fluorescent PCR,then,the above the growth performance of the two-factor variance analysis,the results showed:(1)the growth performance of allogynogenetic silver crucian carp significantly correlated with oil source(P < 0.05);after the bile acid was added in the diets,no significant effect was observed under the interaction between bile acids and different oil(P > 0.05).(2)The highest content of 10 bile acids in gallbladder bile was TCA,with 74.68-83.61% in all four treatment groups.(3)The addition of bile acid in the feed significantly reduced the serum TC content(P < 0.05).(4)In the four treatments,the contents of bile TBA and TC in group O were the highest.Compared with BO2 group,the expression of CYP7A1,CYP8B1,CYP27A1 and FABP m RNA in group O liver were significantly down-regulated(P < 0.05),and BSEP and HMGCR m RNA significantly increased(P < 0.05).(5)The content of TBA in group O was significantly lower than that in group F(P < 0.05),and bile acid(BO2 group)significantly increased(P < 0.05).The expression of intestinal CYP27A1 and ASBT m RNA in group O were significantly down-regulated(P < 0.05),while BABP m RNA was significantly up-regulated(P < 0.05),BO2 group had the opposite effect.(6)After the bile acid was added to the diets,the TC content of the intestine decreased significantly(P < 0.05),while the intestinal HMGCR m RNA significantly increased(P < 0.05).Experiment 3: After the breeding experiment,selected fish group F,O,BA1,BA2,BO1 and BO2,charged with Cy HV-2,then,analysised the cumulative mortality statistics,computing relatively immune protection,detection of blood immunological indexes and the change of the serum bile acid content,the results showed:(1)after infection,relatively immune protection against group F was,O group-10%,BA1 and BA2 group were 45%,BO1 group 35% and BO2 was 35%.(2)in the whole process of poisoning experiment,white blood cell count results of bile acid adding group significantly higher in group F,O group(P < 0.05),and the rising trend,while the rise in group F down before,O group had always declined;there was no significant difference between all groups in the blood hemoglobin concentrations of crucian carp(P > 0.05).(3)Adding bile acid to the diets also significantly increased the serum lysozyme activity of carassius auratus gibelio(P < 0.05).(4)Serum total bile acid content had a same the general trend of reduction,at D3(charged 3d)and D7(charged 7d),bile acid adding group were significantly higher than that of group F and O group(P < 0.05).To sum up,the addition of bile acid in diet can improve the antioxidation ability of allogyogenetics silver crucian carp,reduce the activity of the transaminase of the fish,improve the permeability of liver cells,and protect liver function.On the other hand,added bile acid in the diet,it can adjust endogenous bile acid synthesis,transport and heavy absorption to keep the body and enterohepatic circulation of bile acid balance of allogyogenetics silver crucian carp,thus reducing intestinal and serum cholesterol levels and increase the intestinal bile acid content and prevent bile acid and cholesterol increases that caused by oxided oil liver.In the end,bile acid promotes the growth of allogyogenetics silver crucian carp,and can enhance the immunity of the fish and improve its resistance to Cy HV-2. |
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