Importance of bile tolerance of Lactobacillus acidophilus used as a dietary adjunct.

Cultures of lactobacilli identified as Lactobacillus acidophilus from the intestinal contents of young calves varied in their ability to grow in broth containing .3% oxgall compared with control broth. Frozen concentrated cultures were prepared from a strain exhibiting low tolerance to bile and from a strain exhibiting high tolerance to bile. Plate counts were comparable from the concentrated cultures before and after frozen storage on lactobacilli MRS agar with and without .15% oxgall. In a feeding trial involving newborn dairy calves supplementation of the diet with the more bile resistant strain of Lactobacillus acidophilus caused greater increases of numbers of facultative lactobabilli in the upper small intestines than did the strain exhibiting lower resistance to bile. It was not possible to determine whether the lactobacilli would prevent intestinal infections in the calves challenged with enteropathogenic Escherichia coli. This portion of the study failed as the challenge with Escherichia coli did not cause infections even in control animals.