Biological cells


Probiotics, Prebiotics and Synbiotics – What is the difference?

Probiotics are live “good” microorganisms, such as bacteria and yeast. Classic examples of probiotics are the yeast Saccharomyces boulardii and bacteria in the Lactobacillus and Bifobacterium families (e.g., Lactobacillus acidophilus, which is found in some yogurts). In horse supplements, common probiotics include Enterococcus faecium, Lactobacillus acidophilus, Lactobacillus casei, and Lactobacillus plantarum. The unit of measurement for probiotics is CFUs or colony forming units, look for supplements with a high number of CFUs.

In contrast, prebiotics are the foods that feed the probiotics. Examples of prebiotics included in equine supplements include fructooligosaccharides (FOS), xylooligosaccharides (XOS), polydextrose, mannooligosaccharides (MOS), galactooligosaccharides (GOS), pectin, and psyllium. Your horse does not digest these food ingredients. Instead, prebiotics are digested by the “good” microorganisms and probiotics in the horse’s digestive system to increase their numbers or activity.2

Synbiotics are a supplement that contains both probiotics and prebiotics.

In horses, veterinarians primarily recommend prebiotics and probiotics for GI-related concerns, such as diarrhea, to encourage the growth of the good microbes and to minimize the invasion and growth of disease-causing bacteria.

For example, antibiotic administration, stress, transport, abrupt dietary changes, and Clostridium or Salmonella infections can potentially alter the normal microbe population in a horse’s large intestine. Study results have shown that pre- and probiotics aid in digestion and gut health. Specifically, probiotics help the horse’s GI tract break down and ferment grass and hay. This fermentation process results in the production of volatile fatty acids that provide a significant energy source to the horse. Probiotics also produce B vitamins (such as biotin, which is needed for maintaining healthy hooves) and other nutrients essential to the horse’s overall health

Finally, the “good” intestinal microbes—yeasts, bacteria, protozoa, and fungi—keep the “bad” microbes (such as Salmonella and Clostridium difficile) from overpopulating the intestines and causing diarrhea and illness.


Boyle AG, Magdesian KG, Durando MM, et al. Saccharomyces boulardii viability and efficacy in horses with antimicrobial-induced diarrhoea. Vet Rec 2013;172(5)128. 10. Oke, S. The science behind equine nutritional supplements. Available at

Landes, AD, Hassel, DM, Funk, JD, et al. Fecal sand clearance is enhanced with a product combining probiotics, prebiotics, and psyllium in clinically normal horses. 53rd Annual Convention of the American Association of Equine Practitioners. 2007. Available at:

Luke M. How to facilitated weight gain in equine with body scores of 1.0-2.5. 54th Annual Convention of the American Association of Equine Practitioners. 2008. Available at

Weese JS, Rousseau J. Evaluation of Lactobacillus pentosus WE7 for prevention of diarrhea in neonatal foals. J Am Vet Med Assoc 2005;226:2031-4

Images used under creative commons license – commercial use (4/29/2016) tracy the astonishing (Flickr)

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