Mechanism Of Metabolites Of Lactobacillus From Mare's Milk On Intestinal Mucosal Barrier In Calf

Calf diarrhea is one of the causes of economic losses in dairy farming.In this experiment,the effect of the metabolites of Lactobacillus.P(MLP)was determined by in vitro antibacterial and antibacterial tests in mice,which provided for the later study on the immune function,blood parameters and the influence of gastrointestinal microbes.The purpose of the experiment 1 was to isolate and identify bacteriostatic MLP from mare's milk,and the molecular weight and amino acid content of the MLP were determined.The purpose of experiment 2 was selected sixty SPF mice divided into six groups,the normal control group,the negative control group,the ampicillin,ciprofloxacin groups and MLP group,respectively.Besides the normal control group,SPF mice in other group received treatment as follows over a period of 15 days with exposure to 80%minimum lethal dose E.coli Ol on day 5:saline solution(negative control),ampicillin(0.001 g/kg),ciprofloxacin(0.13 g/kg),Nisin(0.002 g/kg)and MLP(0.125 g/mL).At the end of the experiment,six samples were analyzed by high-throughput sequencing.In this study,high-throughput sequencing was used to study the effect of MLP on intestinal microflora in diarrhea mice.The purpose of experiment 3 was selected twenty Holstein calf divided into four groups,the natural control group,the diarrhea group,ciprofloxacin group and MLP group.In addition to the natlral control group,the other three groups of calf were orally inoculated with pathogenic E.coli 01(2.50 × 10~11 CFU/mL,100 mL/head)to establish a model of diarrhea.After 3 days of modeling,the saline solution was sterilized.0.5 mg/kg ciprofloxacin and 200 mL MLP test samples were mixed with acidified milk for 15 days,twice a day.At the end of the experiment,the samples were collected from serum,ileum,rumen fluid,cecum and colon samples for related indicators to study the mechanism of the MLP on the intestinal mucosal barrier of E.coli 01.The results of this study were showed as follows:Experiment 1:Isolation and identification of 4 strains of Lactobacillus from mare's milk,the similarity with the standard strain of Lactobacillus at the genus level reached 97.80%,It was identified as Lactobacillus and named as Lactobacillus.P,and the MLP was determined by in vitro test.The minimum inhibitory concentration(MIC)was 62.50 mg/mL.The MLP is rich in proline,and the molecular weight of the MLP was determined to be 76.46%within 1000 Da,which was determined to be bacteriocin.Experiment 2:MLP increased the concentration of adamtsl and TC in the jejunum,resulting in a decrease in INS in the ileum(P<0.05).MLP increased the abundance of Lactobacillus,reducing the abundance of Proteobacteria(P<0.01),it can regulate the dynamic balance of intestinal flora.Experiment 3:? Compared with the natural control group,diarrhea group and ciprofloxacin group,MLP increased the levels of IgA,IgG,CD4 and IFN-? in serum,and increased the body weight and levels of adamtsl,TC and INS in ileum.It increased the concentration of Claudin-1,Occludin and JAM-1 in the colon;it reduced the levels of TNF-? and IL-6 to enhance the intestinal mucosal immune barrier and mechanical barrier function(P<0.05).?Sequencing of rumen fluid,cecal and colon microbes by 16S rDNA showed that MLP and ciprofloxacin increased the number of OTUs in the cecum and decreased the number of OTUs in the colon(P<0.05).On the other hand,MLP increased the abundance of Porphyromonas(P<0.05),reducing Helicobacter in rumen fluid(P<0.05).The abundance of Faecalibacterium in the cecum and Fusobacterium in the colon(P<0.05),thereby increasing the microbial barrier function of the gastrointestinal mucosa.In summary,MLP can effectively improve the immunity of pathogenic E.coli 01 diarrhea cattle and the gastrointestinal microflora.MLP is related to animal flora richness in improving animal health and enhancing immunity.Oral metabolites of probiotic are one of the effective ways to enhance the intestinal mucosal immune barrier by regulating the gastrointestinal microbiota.Our findings suggested that metabolites of probiotic have provided interesting insights into future development of probiotic-based strategies to improve animal and human health.