Isolation And Biological Characteristics Of Lactic Acid Bacteria And Bacillus From Gastrointestinal Tract Of Weaned Piglets

At present, the common method for the control of piglet diarrhea is antibiotics, but it will cause the occurrence of antibiotic-resistent bacteria and the antibiotic residue in the animal products. The control of diarrhea with probiotics is not only safe, no residue and resistance, but also can increase feed utilization rate, promote animal growth and improve product quality. But low efficacy and high cost are the limiting factors for the practice of the method. The objectives of this study are to select probiotics with high control efficacy for diarrhea and easy to manage in agent production from piglets intestines, and to study their functions and biological characteristics, in order to provide materials and technology for the production of high efficient products. The paper contains three parts.Part one:Isolation and identification of lactic acid bacteria and Bacillus from gastrointestinal tract of weaned pigletsTo develop excellent live microbial dietary supplements for swine,10bacteria were isolated from gastrointestinal tract of healthy weaned piglets. Based on the results of morphology, phusiology and biochemistry, six isolates(named WR, KR,MR,HR,JR and ZR) were characterized as Lactic acid bacteria from stomach, jejunum, coecum, ileum, colon and rectum. The other four isolates (named WY,SY,KY and HY) were characterized as Bacillus from stomach, duodenum, jejunum and ileum. According to the sequence analysis of16S rRNA, the isolates WR,KR,HR and JR were identified as Lactobacillus salivariu; ZR was Lactobacillus johnsonii; MR was Enterococcus faecalis; WY, SY and KY were Bacillus subtilis; HY was Bacillus cereus. The growth curves of10isolates were different in the culture media, the highest growth rate of HR, ZR and WY was reached at hour12,12and20post-beginning-culturing, respectively, showing the bacteria have satisfactory cultural characters.Part two:Biological characteristics of lactic acid bacteria and Bacillus isolated from gastrointestinal of weaned pigletsTo research and analysis about biological characteristics of lactic acid bacteria (WR,KR,HR,MR,JR,ZR)and Bacillus (WY,SY,KY,HY)isolated from gastrointestinal of weaned piglets.10strains cultured16hs in0.3,0.6(g/ml%) of these two bile salt content of the medium, can be growth and reproduction, shows the10strains tesistant to bile salts have a certain ability. WR,KR strain, deal with simulated gastric of pH3for12hs, the number of viable has increased; other eight strains are reduced, but remained in the same order of magnitude (108cfu/mL), showing8strains has a good tolerability to the simulated gastrointestinal fluid. All isolated strains does not affect their growth dealed with45℃-55℃for30minutes. The inhibitory rate of6lactic acid bacterias was more than80%to E.coli. The inhibitory rate of WR was0to Salmonella, others was more than40%, in4bacillus,the inhibitory rate of KY and HY were more than80%to E.coli. and Salmonella,the ihibitory rate of WY and SY was under0%.With previous test results that KR,HR,MR,JR,ZR,KY,HY can be used as a good candiadate for probiotic bacteria.Part three:Effect of Lacrobacillus salivarius HR on animal gut microflora and growth performanceTo study the prebiotic effect of Lactobacillus salivarius HR, changes of bacterial flora from feces of alteration of intestinal flora mice were studied after oral administration of HR, using techniques of PCR-DGGE and16S rRNA, and changes of Growth performance of Weaned piglets were also studied after oral administration of HR. The DGGE profiles from total bacteria of feces showed some new predominant bands appeared after oral administration of HR for5-10days. On day15after oral administration of HR, this new predominant bands almost disappeared except one. Sequence analysis indicated that the new predominant band was Lactobacillus salivarius. The average growth rate of mice treated with HR was significantly higher than spontaneous recovery group (P<0.05). This suggests that Lactobacillus salivarius HR from swine has a strong resistance and proliferation in the gastrointestinal tract, and can regulate the intestinal germ community and promote the growth of mice. In experiment of Weaned piglets,compared with control group, the HR group was significantly lower(P<0.05), suggesting that Lactobacillus salivarius HR can be used as a good probiotic for swine.