Isolation And Identification Of Probiotic Bacillus From Tibetan Pigs And Screening Of Candidate Probiotic Strain

Antibiotics can reduce the incidence of animal diseases, and improve the performance of animal growth and the economic efficiency of the breeding industry. However, with the overuse of antibiotics, problems, such as drug resistance and antibiotic residues in animal products appear. Probiotics from micro-ecological preparations can regulate the micro-ecological balance of animal bodies in the gastrointestinal tract, so as to prevent diseases and improve the performance of animal production. Therefore, the use of micro-ecological preparations as an alternative to antibiotics has become a trend, and the bacillus preparation is widely used because of its high resistance to stress. Tibetan Pigs, endemic to China, are national herbivorous pig species of plateau grazing type. Tibetan Pigs have strong adaptability so that they can grow and reproduce in low-oxygen, cold environment of Tibetan Plateau, relying on grass and other crude fiber as nutrients. The sickness rate of Tibetan Pigs is quite low. Therefore, the development of Tibetan Pig resources has considerable prospects.In the experiment, the feces of healthy Tibetan pigs in Linzhi area of Tibet province were used as test materials, from which potential probiotic Bacillus were isolated. First of all, the healthy Tibetan Pig feces filtrate adopted the 90?watercuring treatment for 10 minutes to kill non-bacillus coli in samples, and then screened Bacillus capable of inhibiting common pathogenic bacteria by antagonistic tests. Through morphological, physiological and biochemical characteristics and 16 S rDNA sequence analysis, the selected strains were identified. Through tolerance tests, enzyme production tests and antibiotic sensitivity tests, the biological characteristics of strains were studied to select the best strains. Finally, the optimal strains were primarily explored in the application of mice and feed. Specific results are as follows:1. Through the antagonism tests, 3 strains of the common pathogenic bacteria(Salmonella enteritidis, Escherichia coli and Staphylococcus aureus), screened from56 strains of Bacillus isolated from 4 healthy Tibetan Pig fecal samples, have a certain inhibitory effect on Bacillus, then by physiological and biochemical tests and 16 S rDNA analysis, SWUN-TP13 and SWUN-TP22 were identified as Bacillus subtilis, SWUN-TP23 as Bacillus amyloliquefaciens.2. By studying the biological characteristics of the selected Bacillus subtilis SWUN-TP13, SWUN-TP22 and Bacillus amyloliquefaciens SWUN-TP23, the result shows that Bacillus amyloliquefaciens SWUN-TP23 has good potential probiotic capabilities. It has strong stability in adverse environment and can produce cellulase, amylase and protease. Bacillus amyloliquefaciens SWUN-TP23 is sensitive to the most commonly used veterinary antibiotics.3. According to the preliminary study of Bacillus amyloliquefaciens SWUNTP23 in the application of mice and feed, it is found that Bacillus amyloliquefaciens SWUN-TP23 can improve the growth performance and immunity of mice to a certain extent, and it has some certain effect on the degradation of Aflatoxin B1.