| This experiment was divided into two parts,test 1 to chicks to 14 age artificial injection of e.coli virus,observe the chicken group minimum lethal dose,median lethal dose and the onset of symptoms,aims to build artificial chicken escherichia coli induced model,so as to provide reliable for subsequent test tapping toxic dose and poison attack model.Test 2 was conducted to study the influence on growth performance of broilers made by novel antimicrobial peptides and synbiotics,which includes bacillus subtilis,lactic acid bacteria,yeast and oligosaccharide.In addition,this experiment studied their immune modulating effect on broilers,both before and after challenge test.So that to provide technical support for developing the functional feed additives with immune regulating effect.Test 1:At the beginning,adjusted the aerobic bacterial count to 1×107 CFU?1×108CFU?1×109 CFU with the plate count method.Then,injected 0.5 milliliter bacteria liquid in different density into the abdominal cavity of each chicken.There are 4 groups and every group has 20 chicks in the preliminary test,among them there is one control group.These chicks were inoculated with doses of saline.After inoculation,recorded deaths of chickens per day and took the minimum doses of inoculation of chick died within 12 hours as the minimum lethal dose in the whole experiment.After the four processes of experiment: feeding test,challenge test,slaughter test and plate vaccination,then injected escherichia coli into chicks.It showed that there were 2 chicks died in 1×1088CFU,7 chicks died in 1×1099CFU within 48 hours,and 9 chicks died in 1×109CFU within 72 hours,which accounts for 41% of the total number(22)in this experiment.In addition,there were 2~3chicks inactive and didn't intake anything,although they were still alive after 72 hours,but viability is very low.Therefore,the highest dose 1x109 group can meet the requirements of median lethal dose?Test 2: selected 400 healthy broilers and divided them into 4 groups,5 repeat in each treatment group,each repeating 20 chickens.Took one group as control group,feeding basal diets;two groups as the synbiotics(including lactic acid bacteria,Bacillus subtilis,yeast and oligosaccharide)group,feeding basal diets +0.3% synbiotics;three groups as antibacterial peptide group,feed basal diet +0.5% antimicrobial peptides;four groups as antibacterial peptide + group synbiotics,feeding basal diets +0.3% antimicrobial peptide +0.5% synbiotics.Test cycle is 14 days,on the 14 th day during experiment;randomly and repeatedly selected 4 broilers to conduct the challenge test with escherichia coli.After observing 24 hours,recorded the mortality of each group and tested the broilers' immunity after challenge test.This experiment showed that,group four can reduce feed conversion ratio,compared with the control group1,group 2,group 3,but the dissimilitude was not obvious(P>0.05);the feed intake of Group2,Group 3rd was greatly lower than the control group(P<0.05),In terms of daily gain,all the experimental groups and control groups showed no significant difference(P>0.05).The bursal index of group 4 before challenge test was significantly higher than the control groups(P<0.05),There were no significant difference among other groups(P>0.05);the thymus,spleen and Bursa indices of group 2 and group 3 were significantly higher than those in the control groups(P<0.05)after challenge test;the thymus,bursal index of group 4 was significantly higher than the control group(P<0.05);spleen has no significant differences with the control group(P>0.05).The Ig A and s Ig A content of chicks in group 2 had significant difference with the control group before challenge test.(P<0.05),Ig A content in Group four had significant difference with the control group(P<0.05),IL-6 and IL-10 in all experimental group and the control group showed no significant difference(P>0.05);Ig A,s Ig A,IL-6,and IL-10 in group 2 after the challenge had significant differences with the control group(P<0.05),Content of IL-6 in group 3 had significant differences with the control group(P<0.05),Ig A content in group 4 had significant differences with the control group(P<0.05).All in all,compared with the control groups,all experimental groups have no significant differences in production performance,but if synbiotics and antibacterial peptides used together,it has a tendency to improve production performance in broilers.What's more,it will improve immune organ indexes of broilers and content of globulin and reduce inflammatory degree after challenge. |
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