Studies On Application Of Fermented Ginkgo-leaves In Aritificial Feed Of Juvenile Blunt Snout Bream(Megalobrama Amblycephala)

The present study was conducted to investigate the effect of Candida utilis and Aspergillus niger combined fermented ginkgo biloba leaves(FGB) on growth performence, immunity, antioxidant capability, lipid metabolism, muscle fatty acids composition and disease resistance against Aeromonas hydrophila(A. hydrophila) infection in juvenile blunt snout bream(Megalobrama amblycephala). The data obtained here may give some instructions for the application of fermented G. biloba leaves(FGB) in this fish as well as other species sharing the same feeding habits.Fishes were fed basal diets cont.(0.00%) or basal diets supplemented with fermented ginkgo biloba leaves FGB1(0.125%), FGB2(0.25%), FGB3(0.5%), FGB4(1.0%), respectively. At the end of the 60-day feeding trial, fish were intraperitoneally infected with Aeromonas hydrophila and mortality rate was recorded for the next 7days. The results showed that:(1) In the aspect of growth performance, compared with the control, final body weight(Wt) and specific growth ratio(SGR) as well as amylase activities in the intestine of group FGB2, weight gain ratio(WG) of group FGB2 and FGB3, moisture content of whole-body of group FGB4, protein content of whole-body of group FGB1 and FGB2 as well as group FGB3, lipase activities in the intestine of group FGB2 and FGB3 as well as FGB4, protease activities in the intestine of group FGB2 and FGB3 were all significantly increased(P<0.05). But the feed conversion ratio(FCR) of group FGB3, ash content of whole-body of group FGB4 were significantly decreased when compared with the control(P<0.05). Furthermore, survival, visceralsomatic index(VSI), hepatosomatic index(HSI), condition factor(CF), dressing percentage(DP) and lipid content of whole-body showed no significant difference in all goups(P>0.05).(2) In the aspect of lipid metabolism and muscle fatty acid composition, compared with control, serum low density lipoprotein cholesterol(LDL-C) of group FGB3, C20:4n-6 content in the muscle of group FGB4, C20:5n-3(EPA) content in the muscle of group FGB2 were all improved significantly(P<0.05). Whereas, serum low density lipoprotein cholesterol content(LDL-C) of group FGB2 significantly reduced(P<0.05). Furthermore, percentage of abdominal fat(AFR), serum triglyceride content(TG), serum high density lipoprotein cholesterol content(HDL-C), serum total cholesterol content(TC), saturated fatty acids content(SFA), mono-unsaturated fatty acids content(MUFA), polyunsaturated fatty acids content(PUFA), C22:6n-3 content(DHA), EPA+DHA and other fatty acids showed no significant difference in all groups(P>0.05).(3) In the aspect of immunity and antioxidant capacity, compared with control, serum myeloperoxidase leves(MPO) of groups FGB1 and FGB2, alkaline phosphatase(AKP) and lysozyme(LZM) activites of group FGB2 increased significantly(P<0.05). While malondialdehyde content(MDA) of group FGB2 and immunoglobulin M activities(Ig M) of group FGB4 decreased significantly(P<0.05). Furthermore, Acid phosphatase(ACP), superoxide dismutase(SOD), catalase(CAT) and glutathione peroxidase(GSH) were not affected(P>0.05).(4) After Aeromonas hydrophila(A. hydrophila) challenge, the relative mortality of group FGB1 and FGB2 were significantly lower than control(P<0.05), however, the highest one is group FGB4.The results of this study indicated that dietary supplementation of 0.125%~0.25% fermented G. biloba leaves could significantly improve the growth performance, intestinal digestive enzyme content, immunity, antioxidant capacity, lipid metabolism, fatty acids composition in muscle and disease resistance of juvenile blunt snout bream.