| Avian pathogenic Escherichia coli and other pathogenic bacteria are very harmful to the development of livestock and poultry breeding industry,and are one of the important public health problems.Lactic acid bacteria,which are beneficial microbes widely existed in human and animal body,are dominant bacteria groups in the intestines,and have the effect of strengthening the immune performance of animals and promoting the growth of animals.The use of lactic acid bacteria compound preparation can reduce the risk of Escherichia coli in Cherry Valley Duck.It is of great significance to protect the health of poultry and the quality and safety of animal food.In this study,lactic acid bacteria from duck origin were isolated from duck intestines,and lactic acid bacteria strains were screened by resistance test to produce lactic acid bacteria compound preparation.The compound preparation was used to study the growth performance,immune development and immune development of Cherry Valley duck under the condition of avian pathogenic Escherichia coli 17(Avian pathogenic E.coli 17,AE17)infection.The effect of intestinal flora.The purpose of this study is to control the infection of Escherichia coli from meat ducks and provide basis for green healthy breeding of poultry.1.Screening of Lactobacillus from duck intestine and preparation of its compound preparation23 strains of lactic acid bacteria were isolated from the intestines of healthy adult ducks.7 strains(number: L531,L621,E5,L522,L3,L4,E1)with strong tolerance were screened by bile salt tolerance and artificial gastric juice.The screening of L4,L621 two strains and laboratory screening were screened through experimental screening of heat tolerance,surface hydrophobicity,self polymerization,CO agglutination with pathogenic bacteria,and in vitro antagonistic pathogenic bacteria.Compound Lactobacillus casei was prepared by compounding 1.2435 Lactobacillus casei.According to the antibacterial activity,the optimum proportion of three strains of lactic acid bacteria was 1.2435:L621:L4 1:1:2.The antibacterial activity of the compound preparation under 1% inoculation was determined by different inoculation quantities,and the bacteriostasis activity of the lactic acid bacteria in the fermentation time of different fermentation time was determined to be the strongest.2.Effects of lactic acid bacteria from duck intestine on the growth performance and immune performance of E.coli AE17 infected cherry duck160 1 days old Cherry Valley ducks were randomly divided into control group(group CK),lactic acid bacteria compound group(group T),control group(group CK-AE17),lactic acid bacteria compound preparation group(group T-AE17).Group CK and group CK-AE17 were fed with basal diet.Group T and group T-AE17 were fed with Lactobacillus compound(1.5 x 108CFU/m L)from 1 days of age.The leg muscles of group CK-AE17 and T-AE17 were injected into the leg muscles to infect Escherichia coli AE17 at 14 day old leg muscles.The results of growth performance showed that the highest body weight and average daily gain of T group increased by6.93% compared with CK group,and the ratio of material to weight decreased by0.89%.The results of immune function showed that the spleen index,thymus index and bursal index in group T were 25%,11.11% and 6.25% higher than those in group CK,respectively.The secretion of SIg A in intestinal mucosa of group T was 1.77,which was significantly higher than that of CK group(1.56)(P<0.05).The secretion rate of group T-AE17 was 2.16 higher than that of group CK-AE17(2).It shows that the lactic acid bacteria compound can promote the growth performance,improve the immune organ index,and increase the secretion of secreted immunoglobulin A(SIg A)in intestinal mucosa when infected with Escherichia coli AE17.3.High-throughput sequencing technology analysis of the effect of Lactobacillus compound preparation on species composition and function of intestinal flora in E.coli AE17 infected cherry valley duckThe 16 S rRNA amplicon of intestinal flora of Cherry Valley duck was sequenced,and the diversity index of intestinal flora in group T was higher than that in group CK.The analysis of microbial community structure at the door level showed that the dominant phylum(abundance less than 1% merger)of the 4 groups were Bacteroides and thick walled bacteria,and T group had unique microphylla verruca.The analysis of the structure of the microorganism showed that the Lactobacillus compound increased the abundance of intestinal flora while reducing the relative abundance of Escherichia coli in the intestinal tract.According to the sequence of 16 S r RNA amplification,the macro genome detection and functional analysis of intestinal microflora found that the microecological preparation could significantly change the intestinal microflora structure in the AE17 infection state,significantly reduce the ratio of Firmicutes/Bacteroidetes ratio,and improve the regulation of the cell cycle and the cell cycle.The related gene content of cell division,transport and metabolism of amino acids,transport and metabolism of carbohydrates,metabolism,transcription,replication,recombination and repair ",and in the defense mechanism,the COG function annotated to the gene content in the group CK-AE17 and the T-AE17 group is higher than the unattacked CK group and the T group.The compound preparation of lactic acid bacteria has good physiological activity.It can improve the growth performance and immune performance of Cherry Valley duck,increase the diversity and richness of intestinal flora,increase the beneficial bacteria,reduce the number of pathogenic bacteria,and play the role of carbohydrate metabolism and amino acid metabolism in the body. |
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