Screening Of Anti-diarrheal Lactic Acid Bacteria And Their Application In The Prevention Of Diarrhea In Weanling Rabbits

China has one of the largest rabbit populations in the world.There are many diseases in rabbit farming,among which diarrhea in weanling rabbits is the most common disease in rabbit farms.And antibiotics are the most common treatment method.In recent years,countries around the world have been pushing for a "no antibiotics" directive in feed,so it is urgent to find safe and effective alternatives to antibiotics.Research found that some lactic acid bacteria can resist the colonization of foreign pathogenic bacteria,in the prevention and control of animal diarrhea,promote animal growth,improve immune function and other aspects of significant effect.It can also effectively reduce the morbidity and mortality of young animals.However,there are few strains with independent intellectual property rights,and most of them are foreign products in the market.Therefore,this experiment aims to screen lactic acid bacteria with anti-diarrheal function and explore their application in preventing diarrhea in pet rabbits,so as to provide strains and theoretical basis for the development of related products.In this experiment,53 rabbit fecal samples were collected for lactic acid bacteria isolation and screened for lactic acid bacteria that could prevent diarrhea in rabbits by in vitro inhibition method.The isolated lactic acid bacteria were identified by 16 S r DNA and further evaluated for their probiotic properties such as acid and bile salt tolerance,antibiotic sensitivity,surface hydrophobicity and self-agglutination.Finally,the screened strains were fed to weaned New Zealand young rabbits.Then after 21 days,the four enteropathogenic bacteria were fed to young rabbits.The preventive effects of the strains on rabbit diarrhea were investigated by their effects on the incidence of diarrhea,growth performance,serum antibodies,blood biochemistry,blood inflammation,duodenal tissue sections,short-chain fatty acids and changes in the flora of the cecum.The main findings are as follows.1.The epidemiological survey of rabbit diseases in Hangzhou area from 2016 to2020: 244 cases of pet rabbits were seen at the Teaching Animal Hospital of Zhejiang University,33.46% were seen for digestive system diseases with symptoms of enteritis,flatμLence,flora disorders,gastrointestinal retardation,and finally developed into diarrhea.2.Screening of lactic acid bacteria against rabbit diarrhea: A total of 97 suspected lactic acid bacteria were screened from 53 fecal samples,and lactic acid bacteria ZJUIDS-R1 and ZJUIDS-R2 were screened by inhibition tests against common intestinal pathogenic bacteria.ZJUIDS-R1 was identified as Enterococcus faecalis and ZJUIDS-R2 as Lactobacillus animalis by 16 S r DNA.3.Evaluation of the probiotic properties of the strains: ZJUIDS-R1 and ZJUIDS-R2 entered the logarithmic growth phase after 8 h of incubation from single colonies,and entered the plateau phase after 14 h of growth;the survival rate was greater than 20% after 3 h of incubation in the environment of p H=1.5,and the survival rate was 10% and 0.9% in the medium of 0.3% bile salt,and the hydrophobic effect was 51.63% and 29.83%;the self-agglutination rate reached 50.71% and 69.11%after 24 h,respectively.They were sensitive to common antibiotics such as penicillin,ampicillin,tetracycline cotrimoxazole and erythromycin.4.Evaluation of the function of Lactobacillus for the prevention of diarrhea in rabbits: Enterococcus faecalis ZJUIDS-R1 and Lactobacillus animalis ZJUIDS-R2 and the combination of both coμLd reduce the rate of diarrhea in weanling rabbits,among which Lactobacillus animalis ZJUIDS-R2 have the best effect due to its good immunomodulatory effect.The two strains could significantly increase the weight of immune organ spleen without significant effects on other growth performance;They could significantly reduce the systemic inflammatory response and increase the concentration of antibodies in the blood;could significantly increase the duodenal VH and V/C and decrease the CL in weaned young rabbits;could change the abundance of flora in the cecum.The anti-diarrheal mechanism may be related to the ability of Enterococcus faecalis ZJUIDS-R1 and Lactobacillus animalis ZJUIDS-R2 to stimulate host immune response to clear pathogens,increase intestinal flora abundance,and maintain intestinal flora homeostasis.In conclusion,a total of one strain of Enterococcus faecalis ZJUIDS-R1 and one strain of Lactobacillus animalis ZJUIDS-R2 are screened from rabbit feces in this study,which have good in vitro antibacterial effects,probiotic properties and safety.These two strains are able to reduce the incidence of diarrhea in weanling rabbits,mainly by significantly improving host immunity and increasing the abundance of flora in the cecum.Both strains have the potential to replace antibiotics and have good clinical application and commercial value.