Screening And Application Of Canine Probiotic Bacillus

Bacterial diarrhea in dogs is a common clinical disease,which is mainly caused by the imbalance of the bacterial population in intestine.Antibiotics plus fluid replacement therapy were applied in treating canine bacterial diarrhea.In recent years,the emergence of resistant strains due to the unreasonable use of antibiotics has made the treatment of bacterial diseases increasingly complicated.Bacillus,which is a good probiotic with safety and resistance,has been widely used in animal husbandry,but there are few reports on its efficacy for dogs.Therefore,this study aims to screen the excellent canine Bacillus and study its effect on animal immune function to lay a certain foundation for the rational use of the dog diet in the future.In this study,Bacillus was isolated from canine feces by heat treatment.A strain of Bacillus was selected by antibacterial test,drug sensitivity test,acid resistance test,resistance to bile salt test and high temperature test.It was identified as Bacillus subtilis by the morphological,biochemical and 16S rDNA sequence analysis and named QY-20.Kunming mice were used to observe the protection of Bacillus subtilis against Salmonella typhimurium-infected animals.Forty-eight mice were randomly divided into SP group,BS group,LB group and SL group.The gavage order was saline,10~8CFU/mL Bacillus subtilis,10%gastrointestinal probiotics and the equivalent mixture of 10~8 CFU/mL Bacillus subtilis and 10%gastrointestinal probiotics with the dose of0.2 mL/mouse.The test period was four weeks.On the 14th and 28th day,3 mice were randomly selected from each group.Blood was collected from the eyeballs,thymus and spleen were aseptically removed and cecal contents were collected to calculate the immune organs index and measure changes in bacterial mass,the collected serum was tested for IgG,IL-4,and INF-?by ELISA.On the 28th day the remained mice of each group were intraperitoneally injected with 3LD50 Salmonella typhimurium,and the death of each group of mice was observed.The number of bacteria in the contents of the spleen and intestines was measured,jejunum paraffin-embedded sections were made.The results showed that with the increase of the number of test days,the weight of Kunming mice in each experimental group increased,and the BS group had the most significant increase.Feeding Bacillus subtilis QY-20 could significantly increase the number of lactic acid bacteria in the cecum of mice and reduce that of E.coli.After feeding with Bacillus subtilis QY-20,the spleen index,thymus index,serum IgG,IL-4 and IFN-?levels in the BS group were significantly or extremely significantly increased compared with the SP group,the thymus index,serum IL-4,IFN-?levels in the SL group were increased significantly compared with LB group.The mortality rate in the BS group was 66.7%lower than that in the SP group,and the mortality rate in the SL group was 16.7%lower than that in the LB group.Feeding Bacillus subtilis QY-20 significantly or extremely significantly reduced the amount of Salmonella typhimurium in the caecal contents and spleen.After the attack,the intestinal damage was the most serious in the SP group,The BS group had the slightest injury,And the SL group had less lesion than the LB group.From the above results,Bacillus subtilis QY-20 can improve the immune function and the resistance to Salmonella typhimurium infection of Kunming mice.Its combined effect with gastrointestinal probiotics is better than the latter alone.