Preliminary investigation of the probiotic potential of Lactobacillus rhamnosus strain GG in horses: fecal recovery following oral administration and safety.

This study was designed to evaluate whether Lactobacillus rhamnosus strain GG (LGG), an extensively studied probiotic organism in humans, can colonize the intestines of adult horses and foals. Lactobacillus rhamnosus strain GG was administered to adult horses at doses of 1 x 10(9) CFU/50kg bodyweight (BW)/day (group 1, 7 horses), 1 x 10(10) colony forming units/ 50kg BW/day (group 2, 7 horses) and 5 x 10(10) colony forming units/50kg BW/day (group 3, 7 horses) for 5 d. Foals received 2 x 10(10) colony forming units/50kg BW/day (group 1, 7 foals) or 1 x 10(11) colony forming units/50kg BW/day (group 2, 7 foals) for 5 d. Fecal levels of L. rhamnosus strain GG in adult horses were low and variable in the 2 lower dose groups. Even in the high dose group, colonization was relatively low. In contrast, more consistent intestinal colonization was present in foals, and colonization persisted for up to 9 d following cessation of administration. No adverse effects were observed in any animal. Clinical studies evaluating this probiotic are indicated in foals. The presence of this organism in the feces of adult horses may only represent passive movement through the intestinal tract, not actual colonization. Consistent intestinal colonization in adults was only achieved with a prohibitively high dose.