Effect of an In Vitro Proximal Gastrointestinal Tract on Viability of Commercially Available Equine Probiotics.
Authors: Berreta Ana, Kopper Jamie J, Alexander Trevor L, Kogan Clark J, Burbick Claire R
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Probiotic Viability in the Equine Proximal Gastrointestinal Tract Probiotics are only therapeutically useful if their constituent micro-organisms survive passage through the stomach and small intestine to colonise the caecum and colon, yet the viability of commercially available equine probiotics under these conditions has never been formally tested—unlike human formulations, which commonly include enteric coating for protection. Berreta and colleagues used an in vitro model simulating the equine proximal GI tract to expose 11 commercial equine probiotic products to conditions mimicking gastric acid, pepsin, and bile salts, testing viability at both physiological pH (approximately 2.5) and at the elevated pH of 4.0 that occurs in horses with high grain intake or certain pathologies. Six of the 11 products showed at least one strain adversely affected by passage through the simulated proximal tract, and notably, four products actually performed worse when gastric pH was increased to 4.0—a counterintuitive finding suggesting that some strains may be less acid-tolerant than previously assumed. Whilst the results indicate considerable variation in strain resilience across commercial formulations, the finding that several micro-organisms appeared unaffected by proximal GI conditions suggests not all equine probiotics require enteric protection. These findings warrant practitioner consideration of individual product composition and strain characteristics, particularly given the widespread use of probiotics in equine practice and the substantial cost—a more critical approach to product selection based on demonstrated viability may improve therapeutic outcomes.
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Practical Takeaways
- •Not all equine probiotics survive the stomach and upper GI tract equally; selecting products with documented viability data or enteric coating may improve efficacy
- •Consider that some probiotic products may lose viability before reaching the cecum/colon, the intended site of action, potentially limiting their clinical benefit
- •Individual micro-organisms within multi-strain products show variable resistance to gastric conditions; product selection should be based on strain-specific viability data rather than general probiotic claims
Key Findings
- •6 of 11 commercial equine probiotic products tested had at least one micro-organism adversely affected by simulated proximal GI tract exposure
- •4 of 11 products showed adverse effects on at least one micro-organism when gastric pH was increased to 4.0
- •Some micro-organisms in equine probiotics demonstrated resilience and were not adversely affected by proximal GI tract simulation
- •Most commercially available equine probiotics lack advertised enteric protection despite microbial viability concerns during transit