| Diarrhea is one of the main diseases that affects the survival of piglets. According to the referents, 39.8 % of the death for piglets is caused by diarrhea. At present, the common method for the control of piglet diarrhea is antibiotics, but it v/ill 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 culture medium both suitable for the growth of lactic acid bacteria and E.coli was selected. Based on nutritional broth medium, through adding 7 kinds of different nutritional factors commonly used in broth culture, it was showed that glucose and Tuwin were favorable for the growth of lactic acid bacteria and disease-causing E.coli. In the nutritional broth medium with glucose and Tuwin, the number of alive lactic acid bacteria and disease-causing E.coli could both reach 108cfu/mL respectively. The optimal medium for lactic acid bacteria and E.coli was selected with orthogonality test, and the results showed the contents and proportion of the medium was containing 0.9% Beef extract,0.7% Peptoin,0.1% Tuwin and 1% glucose.128 strains of lactic acid bacteria were isolated from the fresh piglets faeces of different breed, time and locale, and 25 strains of them can inhibit the growth of disease-causing E.coli. Through the comparison of the characteristics as acid tolerance, Bile tolerance and growth rate, it was confirmed that the strain with serial number 1-3 was best in integrated performance. Further check-up indicated the strain 1-3 was L.pentosum, and its growth temperature was 15°C~45°C and initial pH4~9 with optimal growthcondition 37°C at pH7.The in vivo test of strain 1-3 preparation in controlling diarrhea was conducted on 90 piglets. The results showed that the diarrhea rate was 8.51% in prevention group, whereas 78.57% in control group. The therapeutic effect of strain 1-3 preparation was studied with the piglets suffering from diarrhea. Treatment was done with the preparation in treatment group and gentamycin was used in control group. The results indicated that the effective rate and cure rate of strain 1-3 preparation was 100% and 76.47% respectively, the average period of treatment was 5d, while the effective rate and cure rate of gentamycin was 93.75% and 31.25% respectively, the average period of treatment was 6 days. Moreover, compared with the control group, the piglets in the prevention group with strain 1-3 preparation showed fine fettle, bright feather and shaped faeces; Even if several diarrhea sufferers appeared, it could be cured in two days with taking-in lactic acid bacteria preparation (once a day).Bacteriostasis mechanism of strain 1-3 was studied. The bacteriostatic tests were done with MRS fermentation liquor, fermentation filtrate and neutralized fermentation filtrate of strain 1-3. The results showed that there were no notable difference in the bacteriostatic effect between fermentation liquor and filtrate, indicating the bacteriostatic substances of strain 1-3 were extracellular metabolite; neutralized filtrate still had the bacteriostatic effect, indicating that except for lactic acid there were other non-acid bacteriostatic substances existed and more research needed to be done on their :egiirJun!.;.iliun and strucLUie. The inhibiting ability of the fermentation liquor existed after 20min treatments at 70°C, 100°C and 121°C, indicating the bacteriostatic substances were heat-tolerant.Medium preparation and cell culture tests were done with tomato and carrot which were cheap and easy to get all year round. It has been ascertained that carrot juice is the optimal basic medium for lactic acid bacteria strain 1-3 with the number of living bacteria reaching to 1.95><108cfu/mL. Taking carrot juice as basic medium, selecting experiments, done on 14 nutritional and growth-promoting factors, discovered Peptone, Glucose, ST and CaCO3 has notable growth-promoting effect on strain 1-3. Through L934 orthogonality test, the optimal medium for strain 1-3 was selected which contains 1% Peptone, l%glucose, 0.1% ST and 0.3%CaCO3. After cultivation of strain 1-3 at 37°C for 16h on carrot juice compound enrichment medium, the living bacteria could reach 1.08x109cfu/mL.The preservation tests of strain 1-3 MRS natural fermentation liquor were conducted under the conditions of 4°C, room temperature, and room temperature plus pH adjustment. The results showed that low temperature was in favor of the living bacteria. The preservation periods were 7.5 days under room temperature and 10 days at 4°C respectively when keeping the living cells over 106 cfu/mL. Adjusting the pH of the... |
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