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Understanding Probiotics and Prebiotics

There has been a great deal of literature available about probiotics and prebiotics. You may be aware that both probiotics and prebiotics are used to improve a horse’s digestive health, but what is the specific purpose of each and when should you add them to your horse’s diet? We’ll discuss the difference between these two supplements, when to use them, which product to use and how much to give.


Probiotics are yeast and live bacteria that are beneficial in the digestive process. Their Latin names are long and difficult to pronounce – Lactobacillus, Saccharomyces, Bifidobacterium and Enterococcus. They are found naturally in dairy products like yogurt. They are normally present in the horse’s gut and promote a healthy digestive process. Probiotics are delicate and easily destroyed by stomach acid and heat. Very few bacteria make it from the stomach in to the digestive tract.


Prebiotics are not the actual yeast and bacteria, but rather a dietary fiber that promotes, nourishes and supports the growth of the Probiotics, or “good bacteria”. They are found in vegetables such as onions, beans, beets and Jerusalem artichoke; and many fruits such as apple skins and bananas contain them as well. They are also present in certain fermentation processes. Prebiotics are not temperature sensitive and are not affected by stomach acid. Hay and grass are an important source of prebiotics.

When Should I Supplement?

No food or feeding area is sterile, so horses are ingesting probiotics every time they eat. If a horse is suffering from a digestive upset, you may notice that it instinctively begins eating manure in an attempt to take in more probiotics. There are times, though, when you will want to consider giving additional supplements.

  • When weaning a young animal to a solid diet to make the transition smoother
  • After long-distance travel or heavy exercise
  • During antibiotic therapy to help replenish the normal gut bacteria
  • When being treated for diarrhea
  • After being treated for colic
  • In the instance of weight loss in an older horse
  • Animals on high grain diets
  • Any digestive upsets or loose manure

Using These Supplements

Use of either prebiotics or probiotics is generally appropriate in most situations. If your horse is on a high grain diet, use of saccharomyces yeast (a probiotic) will help decrease acidity in the large gut. To promote weight gain and efficient feeding patterns, a prebiotic derived from fermented Lactobacillus is helpful. Unfortunately, our knowledge of use of these supplements is not complete yet. There are specific dosing and storage guidelines, however.

  • Prebiotics and probiotics are measured in CFUs or colony forming units. The recommended minimum dose is ten billion CFUs.
  • Most bacteria are destroyed in the stomach, but quickly multiply in the gut.
  • Better quality prebiotic formulas contain high levels of the “good” bacteria.
  • Because of stability issues, live organism prebiotics are often a better choice than probiotics.
  • Use “live organism” formulations for the best results.
  • Always store all containers in a refrigerated area in a tightly sealed container to assure stability of the product.
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