This study investigated lactic acid bacteria (LAB) isolated from bovine samples, and evaluated the colonization ability, fecal recovery and safety of one isolate with probiotic properties in a 15-day blind placebo study in calves. 104 LAB were assessed 'in-vitro' for resistance to low pH, bile salts, aerobic incubation, and antimicrobial activity against ' Escherichia coli' F5 and O157. Fourteen and 42 percent of the isolates had appropriate overall tolerance (growth rate >80% compared to controls) to pH 4 and 0.3% bile. The inhibitory effect of LAB supernatants on ' E. coli' was associated to their low pH (r2 = 0.804, ' p' < 0.001). The selected isolate (LPB80) was identified as ' Lactobacillus plantarum' by 16S rRNA-PCR. LPB80 administration had no adverse effects. LPB80 was recovered from feces of treated and non-treated calves and from intestinal samples of treated calves. Results suggested that oral administration of LPB80 is safe and that LPB80 may colonize the intestinal tract of calves.