| Calf diarrhea is the main cause of death in lactating calves.It is divided into two types:viral and bacterial diarrhea.Escherichia coli is the main pathogen of bacterial diarrhea.Previous studies have shown that Lactobacillus plantarum can alleviate calf diarrhea caused by Escherichia coli,but the mechanism is unclear.To this end,the model animal mice were used to observe the changes of serum cytokines,intestinal barrier,and intestinal flora of Lactobacillus plantarum on bovine-derived Escherichia coli diarrhea mice.The contents of this study are as follows:Sixty 8-week-old healthy female BALB/c mice（initial weight 20±3 g）were randomly divided into 5 groups with 12 mice in each group.The bacterial concentrations of saline（C）,Lactobacillus plantarum（Y）or Escherichia coli（Z）,0.1m L/10g,Lactobacillus plantarum or Escherichia coli perfusion solution were determined according to the pre-test results,which were 1×10~8 CFU/m L and 1×10~7 CFU/m L,respectively.Mice in group C were fed with normal saline,mice in groups Y and Z were fed with Lactobacillus plantarum or Escherichia coli respectively,mice in group YZ were fed with lactobacillus plantarum for 10 days,and mice in ZY group were fed with E.coli for 5 days and Lactobacillus plantarum for 10 days.During the experimental period,the health status of mice and the number of diarrhea and death were recorded every day.Samples of tissue and intestinal contents were collected at the end of the experiment.The results are as follows:1.Lactobacillus plantarum significantly increased the daily weight gain and feed intake of mice,and the daily weight gain and feed intake of each Lactobacillus plantarum feeding group were higher than those of the Z group（P<0.05）;it could also reduce diarrhea in mice,compared with the Z group,the diarrhea rate of the mice in the YZ group decreased by 66%,and the ZY group decreased by 41%;the thymus index and spleen index of the mice in the Y group were significantly higher than those in the Z group（P<0.05）.The difference was not significant,indicating that feeding Lactobacillus plantarum promotes,and feeding Escherichia coli inhibits the development of immune organs.2.The preventive intervention effect of Lactobacillus plantarum was better,the administration of Lactobacillus plantarum significantly increased the content of Ig G and Ig M in serum,and the Ig G and Ig M in the YZ group were significantly higher than those in the ZY group（P<0.05）;the serum levels of the Y and YZ groups were significantly higher.The contents of anti-inflammatory factors IL-4 and IL-10 in serum and jejunum of Y group and YZ group were significantly higher than those in Z group（P<0.05）.The content ofγwas significantly lower than that in the Z group and the ZY group（P<0.05）,indicating that feeding Lactobacillus plantarum promoted and fed Escherichia coli inhibited the immune function of the body.3.Lactobacillus plantarum significantly reduced the intestinal permeability of mice.The serum DAO and LPS of the Y group and YZ group were significantly lower than those of the Z group（P<0.05）;the s Ig A of the Y and YZ groups were significantly higher than those of the Z group（P<0.05）,indicating that Lactobacillus plantarum can promote the immune function of the intestinal mucosa of mice and enhance the intestinal barrier function;Compared with the ZY group,the proportion of CD3+and CD8+in the spleen of the mice in the YZ group was significantly increased,and the proportion of CD4+was significantly decreased.It shows that Lactobacillus plantarum preventive intervention can alleviate the cellular immune suppression caused by Escherichia coli infection,and make the immune system of the body tend to be normal.4.Lactobacillus plantarum can improve the diversity and uniformity of cecal microbial community.Compared with the Z group,the Lactobacillus plantarum group increased the proportion of Bacteroidetes and Actinobacteria,and decreased the proportion of Firmicutes,indicating that Lactobacillus plantarum promotes a beneficial shift in the gut microbiota in mice.5.The main differential metabolites between blank control group（C）,prevention group（YZ）and treatment group（ZY）were prostaglandin endoperoxide（PGH2）and succinic acid,and the abundance of PGH2 in ZY group was extremely significant higher than that in group C and group YZ（P<0.01）;the abundance of succinic acid in group YZ was significantly higher than group C and group ZY（P<0.01）,indicating that Lactobacillus plantarum may mediate immune response and promote immune response by synthesizing PGE2 TCA cycle,improve energy metabolism,and then enhance the body’s immunity.6.Metabolites are regulated differently under different intervention timings of Lactobacillus plantarum.Compared with the C group,the differential metabolites between the YZ groups were mainly enriched in the NF-κB signaling pathway,the MAPK signaling pathway,and the differentiation of Th1 and Th2 cells;the differential metabolites between the ZY groups were mainly enriched in arginine and arginine.The proline metabolic pathway regulates the body’s inflammatory response.The above results show that plant lactobacillus can increase the daily weight gain and feed intake of mice,reduce the rate of diarrhea,promote the development of immune organs,promote the anti-inflammatory factors IL-4 and IL-10,and inhibit the pro-inflammatory factors IL-2 and IFN-γexpression reduces intestinal permeability in mice,enhances intestinal barrier function,and improves intestinal microflora.In addition,the preventive intervention effect of Lactobacillus plantarum was better. |
