| The industry of tilapia culture is becoming more and more important because mostof products were exported to those American and European countries.Aquaculturefarmers resort to high-density feeding mode and misuse large antibiotics in order tomake more profits,which result in severe consequences such as the outbreak of massdisease and hazard of food safety.Therefore, new immunostimulants should bedeveloped so that not only increase the output per unit area but also enhance thequality of fish product.In this study,two different types of immunostimulants wereanalyzed to find out their effects on nonspecific immunity and the resistance ofenvironmental stress.The study consists of three partes and the main results asfollows.The aim of the first part was to study the effect of a chinese herbal formulaadditive on non-specific immunity in blood of Nile tilapia (Oreochromis niloticus).Different mixed fish feeds were prepared at different ratio of chinese herbal formulaadditive (0%(control group),1%(A group),3%(B group),6%(C group)) which containshouttuynia cordata thunb, Scutellaria baicalensis, Isatis root and other seven chineseherbs.Nile Tilapia （body wight54±0.32g）were fed with different mixed fish feedsfor12weeks and the serum immune indexes,including malondialdehyde content(MDA), lysozyme activity(LSZ),superoxide dismutase activity(SOD) and NOcontent were examined at4th,8th and12th week,respectively.Whole blood immuneindexes,i.e. phagocytosis percentage (PP),phagocytosis index (PI) and respiratoryburst activity) were examined respectively at12th week.The main results andconclusions are as follows:from the8th week, the serum MDA of Nile tilapia blood inGroup B decreased significantly (P＜0.01) as well as in Group C;In C group,Niletilapia blood SOD activity and NO content increased significantly (P＜0.01)together with LSZ activity improved (P＜0.05) compared with that in the controlgroup.At12th week,Nile tilapia blood SOD,respiratory burst activity of haemocytes,LSZ and NO content in Group B started to elevate.Meanwhile,SODactivity,NO content,MDA content,phagocytosis percentage(PP),phagocytosis index(PI)and respiratory burst activity of haemocytes in Group C increased significantly (P＜0.01) compared with those in the control group.The results suggest that fish feedadded with3%and6%chinese herbal formula additive can enhance the non-specificimmunity of Nile Tilapia and fish feed added with6%chinese herbal formula additiveis recommended especially.The second part was based on the first part that Nile Tilapia fed with6%chineseherbal formula additive can enhance the non-specific immunity.This study wasconducted to determine the effect of fructooligosaccharides added in chinese herbalmedicine compound based feed on immunity in Nile tilapia (Oreochromis niloticus).Different ratio of fructooligosaccharides (0g/kg(control group),1g/kg (Agroup),3g/kg(B group),5g/kg(C group)) were mixed in basic feeds added with6%chinese herbal formula additive which contains houttuynia cordata thunb,Scutellariabaicalensis, Isatis root and other seven chinese herbs.Nile Tilapia were fed with thesemixed feeds for90d and the serum immune indexes were examined at30d,60d and90d week,respectively.Besides,the fish were experimentally infected withStreptococcus agalactiae at the end of the experiment.The results showed: bloodserum lysozyme activity(LSZ) and Catalase(CAT) of A group were both elevatedsignificantly on the60d(P＜0.05),which reached to the top level on the60d and90drespectively.In addition,superoxide dismutase activity(SOD) of A group wassignificantly higher than the control group on the30d reaching to the top level on the30d(P＜0.05) while MDA contents in each time was significantly lower than thecontrol group at its lowest on the90d(P＜0.05).There were no signiticant differencein both serum alkaline phosphatase (AKP) and NO contents of A group(P＞0.05).Blood serum lysozyme activity(LSZ) and alkaline phosphatase (AKP) of B groupwere both elevated significantly on the60d(P＜0.05),which reached to the top levelon the60d and90d respectively.In addition,superoxide dismutase activity(SOD) andCatalase(CAT) of B group were significantly higher than the control group on the30dreaching to the top level on the60d and90d respectively(P＜0.05) while MDAcontents in each time was significantly lower than the control group at its lowest onthe60d(P＜0.05).There were no signiticant difference in serum NO contents of Bgroup(P＞0.05).Compared with A group, superoxide dismutase activity(SOD) andalkaline phosphatase (AKP) of B group had significant difference on the60d while Catalase(CAT) on the90d (P＜0.05).There were no significant difference for C groupon all tested serum immunoenzyme compared with the control group at each samplingtime(P＞0.05).The immune protection of A and B were55.81%and67.44%,respectively,both of which were much higher than control group.The immuneprotection of C group was6.9%with little effect.The last part is to further study the effects of fructooligosaccharides on tilapia(Oreochromis niloticus) cortisol and glucose contents of serum under twoenvironmental stresses.Different ratio of fructooligosaccharides (0g/kg(control group),1g/kg (A group),3g/kg(B group),5g/kg(C group)) were mixed in basic feeds addedwith6%chinese herbal formula additive.Nile Tilapia were fed with these mixed feedsfor90d and then some were conducted with bacteria stress trial and the others wereexposed to crowding stress (35g/L) for48h.Cortisol and glucose contents of serumwere investigated at0h,3h,12h,24h,36h and48h,respectively. The results of bacteriastress showed that the cortisol and glucose contents of all groups had been elevatedgreatly after exposed24h,of which A group and B group had significantly differencecompared with the control group(P＜0.05).As time went by, the contents of all groupsbegan to decrease, and eventually the test group had parallel to the control group. Thecrowding stress results showed that all of the groups had a same trend with the resultsof bacteria stress test.The difference between these two tests was that the cortisol andglucose contents of the latter one were reaching to the top level on the12h and24h,respectively.It concluded that1～3g/kg fructooligosaccharides can enhance the abilityof resistance to harsh environment condition. |
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