| Escherichia coli diarrhea is a common disease in swine breeding industries, which caused huge economic loss in the pig breeding industries. ETEC is the most common reason to rise escherichia coli diarrhea, especially during the weaning period of piglets when the factors changes more fast both Inside and outside the body and it is the time for diarrhea comes easily.PSIP-409-FaeG-DC recombinant lactic acid bacteria has been made and saved by our group. The recombinant bacteria is fused FaeG gene which on K88 fimbriae and DCpep, joining again pSIP-409 carrier and then to be expressed in lactic acid bacteria. The bacteria has practiced on mice. On the basis of this study, we applied the recombinant lactobacillus pSIP-409-FaeG-DC to piglet, researching its effects of immune protection on piglets diarrhea, which has improved to has good effect. Addition to it, we evaluated the possibility of the lactic acid bacteria used in vaccine production in the future. The specific research contents and results are as follows:First of all, we determined the best attack toxic doses.12 head piglets were randomly divided into three groups, each group of 4 head, filling and take different concentrations of e.coli bacteria liquid induced diarrhea piglets, and setting concentration to 6 x 107 cfu/mL 、6 x 108 cfu/mL and 6 x 109 cfu/mL. We often observed the degree of diarrhea, which reflected by fecal score. The results showed that the 6 x 109 cfu/mL is the best drug doses to attack.After determining the best attack toxic dose, we did the research of the immune protection effect of the lactic acid bacteria. We chosed 40 weaning pigs, their age are(28 + 2)day, and the average weight was(8.06±0.31)kg. The boars randomly divided into A, B, C, D group, 10 head each group. The first week, we fed the pigs of group A MRS culture medium every day, group B and C intake lactic acid bacteria(the daily intake of 5 x 108 CFU). The bacteria was put into water and mixed with fodder. The group D was empty group; in the second week, we did ETEC poison attack. The groups A, B fed e.coli 5mL which dose was 6 x 109cfu/mL, group C fed physiological saline of 5mL, group D was empty group. After Two weeks, all the pigs were slaughtered. During our experiments, we observed the changes of weight and the ratios of the weight and fodder to reflect the growth performance. Besides, we recorded the fecal scoring and routine blood in order to improving the recombinant lactic acid bacteria can relief the diarrhea of pigs. In addition, we did the detection of the intestinal contents、made pathological slices and placed the intestinal villus under the scanning electron microscopy, investigated the from the micro level. And we did MTT test to measure their effects on the immune.Test results showed that the weight of group A decreased significantly, and group B also decreased a little, the weight of group C and group D increased normally, no significant difference(P﹥0.05). The change of body weight showed that the lactic acid bacteria played a good role on the protection of, effectively relieve the diarrhea of piglets, it rather can promote the growth of piglets; The F/G of group A is higher than that of group B, which explained the production performance of group B is higher than that in group A, but there was no significant difference(P﹥0.05).All of these improved the lactic acid bacteria has ability to resist diarrhea, but the action on improve production performance is not particularly significant; From the point of the intestinal contents monitoring results, the number of e. coli of group A and group B extremely significant difference(P﹤0.01), the group A was significantly higher than group B. The number of anaerobic bacteria of group A and B extremely significant difference(P﹤0.01) from group C and D, and the The former is significantly higher than the latter. The test showed that the recombinant lactic acid bacteria can reduce the number of intestinal escherichia coli, increase the number of probiotics; What did we learn from pathological, recombinant lactic acid bacteria have good protective effect on intestinal; As you can see in scanning electron microscopy figure, the restructuring of lactic acid bacteria in the micro level also played a good protection, can protect fluff from ETEC; According to the result of lymphocyte transformation test, group B of piglets in the peripheral blood lymphocyte proliferation ability and extremely significant difference compared with group A(P﹤0.01), the overall effect of justifying the the probiotics can enhance the body’s immune system as a whole.In conclusion, the reorganization of the lactic acid bacteria can enhance the growth performance of piglet, reduce diarrhea, protect the intestinal villus, improve body immunity, is a remarkable probiotics, utility for ETEC vaccine research and development has laid a solid foundation. |
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