Effect of an In Vitro Proximal Gastrointestinal Tract on Viability of Commercially Available Equine Probiotics.

Abstract Probiotics, by definition, are live micro-organisms and should remain viable when they reach the intended site of action which is typically the cecum and/or colon. In humans, probiotics often need enteric protection to survive transit through the proximal gastrointestinal (GI) tract. Typically, equine probiotics do not advertise enteric protection and to the author's knowledge the viability of equine probiotics after exposure to the proximal GI tract has not been evaluated. The objective of this study was to evaluate the effect of an in vitro simulation of the equine proximal GI tract on probiotic viability. We hypothesized that the simulated proximal GI tract would adversely effect microbial viability and that the adverse effects would be partially ameliorated by increasing the gastric pH to 4. A total of 11 products were evaluated of which six had at least one micro-organism that was adversely effected by exposure to the proximal GI tract and four of which had at least one micro-organism that was adversely affected when the gastric pH was increased to 4.0. Results from this study indicate that some micro-organisms in equine probiotics do not appear to be adversely affected by exposure to the equine proximal GI tract.