Preparation Of Lactic Acid Bacteria Preparation And Its Preliminary Application In Preventing Diarrhea In Weaned Piglets

Post-weaning diarrhea(PWD)has always been a problem for the pig industry,causing huge losses to the global economy every year.At present,it mainly relies on antibiotics to prevent and control the incidence of PWD,and there is not a significant decline.Studies have shown that probiotics have a good effect as a supplement.However,the preparation of lactic acid bacteria has problems such as weak effect and difficulty in storage.Therefore,this study aims to prepare high-quality lactic acid bacteria(Se Ag-LAB)and selenium,silver nanoparticles(Se Ag-NA)originated from lactic acid bacteria source to enhance the use of lactic acid bacteria in clinical use,and prevent the disease occurs.First,we investigated the epidemiology of PWD in Heilongjiang pronince,and then prepared Se Ag-LAB,Se Ag-NA,and then carried out animal experiments to analyze the protective effect of Se Ag-LAB and Se Ag-NA on intestinal damage caused by ETEC K88 infection.The result is as follows:Epidemiological studies have revealed 238 pathogenic E.coli isolated from 248 stool samples from diarrhea in weaned piglets in Heilongjiang Province.The results showed that the positive rates of F4,F18 and F41 were 8.4%,11.34% and 27.73%,respectivel y,and the positive rates of STa,STb and EAST1 were 44.96%,28.15% and 20.59%,respectively.Compared with the literature reports,the detection rate of F41 fimbriae genes increased,and the detection rates of toxin genes such as STa and STb increased,but the detection rates of virulence genes in different regions of different countries were different.The measurement results of the biofilm formation ability showed that about 70% of the strains had medium-strong biofilm formation ability,and 99% of the strains showed multi-drug resistance.The results of genetic clustering showed that type A was the main type,reaching 69.54%.After that,we screened LAB strains suitable for preparing Se-Ag-rich LAB,and obtained optimum working conditions.The highest concentration of sodium selenite and silver nitrate were 320 ?g/m L,and the ability to convert selenium and silver is relatively stable.A room temperature resistant Sa Ag-LAB preparation and Se Ag-NA were prepared.Se Ag-LAB preparation can improve the survival rate of lactic acid bacteria,and obtain two formulations.The formulation 3 components are skim milk 15%,trehalose 5%,mannitol 0.3%,and the formulation 4 components are gelatin 4%,casein 8%,glycine 1%.The survival rate of lactic acid bacteria stored at room temperature for 3 months can be maintained at 105-106(CFU/g).Then,Se Ag-NA was observed by electron microscopy and the antibacterial effect of Se Ag-NA was analyzed.To evaluate protective effects of Se Ag-LAB and Se Ag-NAon the intestinal mucosa damaged by ETEC K88,a mouse model was used for animal experiments.Control group,K88 infection group,and Se-Ag-rich lactic acid bacteria group(Se Ag-LAB+230 group),lactic acid bacteria source Se-Ag nanoparticle group(Se Ag-NA+230 group),was setted.Antioxidant-related indicators,cytokines and intestinal mucosal barrier-related m RNA expression levels were detected.The results showed that both Se Ag-LAB and Se Ag-NA promoted the production of GSH-Px,which could alleviate the damage of MDA cells and promote the expression of cryptdin-1,mucin-2 and TLR-2 when ETEC K88 was infected.Se Ag-NA Inhibition of IL-6 expression has the function of inhibiting the occurrence of inflammation;the application of Se Ag-LAB and Se Ag-NA has a protective effect on the intestinal mucosa of ETEC K88-infection mice.Secondly,in order to evaluate the effect of Se Ag-LAB and Se Ag-NA on promoting growth,animal experiments on piglets showed that Se Ag-LAB and Se Ag-NA have growth-promoting effects as feed additives.A safe,effective,and suitable for room-temperature-preservation preparation of lactic acid bacteria and a new selenium,silver nanoparticles(Se Ag-NA)originated from lactic acid bacteria source was prepared in this study,could be used to improve animal health as a supplement,help to improve the production efficiency of the breeding industry,improve the immunity of piglets,promote piglet weight gain,and improve feed conversion rate.It is expected to be used in clinical prevention of diarrhea in piglets,providing theoretical basis and basis for clinical application.