Selection of probiotic bifidobacteria for lambs

Twenty-six bifidobacteria were isolated from faecal samples of lambs. The isolates were identified, functional properties (survival ability at low pH and bile conditions) and antimicrobial activities against potential pathogens were determined. From the isolates with suitable properties (13 strains) rifampicin-resistant mutants were prepared by gradient plate techniques. This property enabled us to differentiate the administered organism from wild strains because resistance to rifampicin is rare among bifidobacteria. Rifampicin-resistant bifidobacteria (RRBifs) were administered to 3-days-old lambs in two trials. In the first trial the strain B. ruminantium L29 was applied to 3 lambs and was detected in faecal samples at high counts (6 log CFU/g on average) for one week. In the second trial 3 lambs received a "cocktail" of 12 strains and RRBifs survived in the intestinal tract at counts of about 6 log CFU/g for 25 days. The control group without probiotic treatment consisted of 6 animals. In both treated groups RRBifs dominated among bifidobacteria after their administration. Total bifidobacterial counts (5.64-7.32 log CFU/g) were significantly higher (P < 0.05) in treated groups compared to 2.31-2.85 log CFU/g detected in the control group during the first month of lamb life. Lactobacilli counts were also significantly higher (P < 0.05) in treated groups compared to the control. The administered bifidobacteria did not affect any other monitored bacterial groups. On the basis of in vitro test results, suitable probiotic bifidobacterial strains for lambs were chosen. Some of them survived for 30 days in the gastrointestinal tract of treated lambs, but no tested strain was able to colonise the lamb's tract permanently. The administration of bifidobacterial "cocktail" and consequent identification of the best survived strain seems to be an effective method for selection of potential probiotics.