Probiotics are live microorganisms taken orally that are said to deliver health benefits. Clearly, to have an effect they need to reach the relevant portion of the gut. In horses, this is thought to be the large intestine – the caecum and colon.
A study by Ana Berreta and colleagues at Washington State University, looked at the effect of the equine gastrointestinal tract on equine probiotics. The work is reported in the Journal of Equine Veterinary Science.
In the laboratory study, they assessed the viability of eleven commercially available equine probiotic products in
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conditions of acidity designed to mimic those in the stomach and the small intestine.
The research team mixed each of 11 of the probiotics with hydrochloric acid at pH2 (to mimic conditions in the stomach). After 30 minutes the pH was raised to 6.9 and enzymes and electrolytes were added to mimic conditions in the small intestine. Then two hours later they cultured each mixture and used mass spectrometry to identify and quantify the microorganisms present.
The experiment was repeated using an initial pH 4 (to represent the conditions in the stomach when proton pump inhibitors such as omeprazole were being used).
They compared these results with those obtained using probiotics straight from the packet.
They found that the gastric pH of 2 adversely affected micro-organisms in six of 11 probiotics. Four of the probiotics had at least one micro-organism that was adversely affected when the pH was increased to 4.0.
The microorganism that was most commonly adversely affected by conditions in the virtual gastro-intestinal tract was Enterococcus faecium. In contrast, Saccharomyces cerevisiae (present in one product tested) actually increased significantly in number after exposure to both pH2 and pH4.
None of the probiotics tested matched their label claim - all of them contained micro-organisms not listed on the label.
The authors conclude that passage through the proximal gastro-intestinal tract may negatively impact the survival of some microorganisms. They suggest that enteric protection should be considered to improve microorganism viability in equine probiotics.
For more details, see:
Effect of the equine proximal gastrointestinal tract on probiotic viability
A Berreta, JJ Kopper, TL Alexander, CJ Kogan, CR Burbick
Journal of Equine Veterinary Science (2021) 104