Screening Of Lactic Acid Bacteria And Study On The Application Effects Isolated From Calf

In order to develop preparation of calf-lactobacillus, probiotic role of lactic acid bacteria was identified on the calves.In this study, the calf intestinal mucosa and chymus chosed as the source for the bacteria, isolated Lactobacillus which have the quality of strong anti-intestinal environment and antibacterial properties.To further qualify the potential of a calf-specific lactobacillus on improve body weight, recta microflora and prevention of diarrhea and will provide theoretic basis to the practice.Thirty one lactic acid bacteria strains, Gram staining masccline and non-spore, were isolated form different (duodenum, jejunum, ileum, caecum and rectum)intestinal tract mucosa and chyme of 15 days healthy calf. Application of in vitro treatment in pH = 2 for 2 hours, with more than 5% survival rate in the standard, selected 9 bacteria in bile tolerance and resistance screening of pepsin.Four strains, M5, M7, SB1 and Z4 were selected through the tests of tolerance bile salt with different concentration and artificial gastric juice. The survivability of strain M5, M7, SB1 and Z4 was 39.24%, 28.08%,44.20% and 23.28% respectly when treated with acid of pH=2 for 2 hours,which survival rates were 44.17%, 70.13%, 32.92% and 29.86% in the bile salt concentration of 0.1% treatment after 2 hours.All of the 4 strains have commendable intolerance ability in bile salt with different concentration.The survivability of the strains were all over 30% in artificial gastric juice. The tolerances of strains were excellent in imitating gastroenteric environments. The bacteriostasis was prominent to Escherichia coli and the diameter of inhibition zone was 16mm~21mm.According to the Carbohydrate fermentation by the traditional method of identification of the four lactic acid bacteria, were preliminarily defined as M5 (L .mucosae), M7 (L .murinus), SB1 (E. hirae), Z4 (E. cecorum). L. mucosae. Through the acid test showed that strains Z4, SB1, and M5 from the culture medium pH, initially 6.25, reduced to the pH 4.52,4.56,4.56 when relatively stable, so the lactobacillus was strong acid production strains. By the growth test, M5 shortest generation time for 89.8 minutes, the viable count reached 1.0×1010 cfu/mL after 10 hours. Comprehensive assessment of each factor, selected the M5 as a probiotic bacteria used for calf production.Ten Holstein calves were randomly divided into two groups (five for each group) based on body weight, with good health of newborn calves. Body weight by analysis of variance between groups, the difference was not significant (p> 0.05). The trial period was 30 days. Born calves fed colostrum from 1 to 4 days ,afterward two groups were fed milk replacer.From the first day , the test group will be adding lactic acid bacteria. Add the amount of bacteria in accordance with 5×108 viable cells per kilogramme body weight given. Calves fed lactic acid bacteria from 1 to 30 days by drinking milk.The effects of lactic acid bacteria M5 on calf body weight, rectal flora and diarrhea rate were evaluated. The results showed that: the experimental group and control group calves were 47.9kg and 46.4kg weight when the trial ended, and two group differences in body weight were not significant (p> 0.05), but the overall growth of the test group to be superior in the control group, and body weight was higher 1.5kg at the average weight than the control group; compared with the control group, fed with lactic acid bacteria M5 can rapidly increase the number of Lactobacillus in fecal at 10 days old calf, but the difference was not significant (p> 0.05); to 30 days ,the number of calf fecal lactic acid bacteria in the experiment group significantly higher than the control group(p <0.05); compared with the control group, fed with lactic acid bacteria M5 can reduce the number of E. coli in fecal at 10 days old calf ,the number of significant differences between the two group (p <0.05), while the control group, the number of E. coli show decreased a clear trend compared with 1 day old but upward trend in the control group; The number of E. coli in the two group decline or upward trend was not obvious when calve get 20 days of age, but the test group the number of fecal E. coli is still lower than the control group, the difference was not significant (p> 0.05); from the whole of experimental period, experimental lactobacillus group and control group were diarrhea, but there are some differences in the degree of diarrhea. Especially , there were the groups difference in diarrhea rate of the control group(8%)higher than the experimental lactobacillus group(2%) from1 to 10 days.