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Equine Health Resource

Diarrhea, Feed Related

Changes in feed can cause digestive upset in horses. This usually occurs when a sudden transition is made from a higher roughage ration to a higher grain ration, but can occur for a variety of other reasons.

Horses have a limited ability to digest starch, and if the proportion in the diet suddenly increases, diarrhea can result. Diarrhea or soft “cow pie” manure may occur because of shifts in the populations of intestinal microbes, and changes in acidity of the gastrointestinal tract.

As with people, some horses simply don’t tolerate certain feeds and will develop diarrhea if it is fed. This may include syndromes comparable to “gluten allergy or intolerance” that are becoming better recognized in people.

The colon does not function properly if there is too high a fiber load. This happens, for instance, in horses that cannot chew their feed. Consequently, diarrhea is common in old horses with bad teeth.

In general, horses with mild nutritional diarrhea are not outwardly ill otherwise. They maintain a good appetite and attitude. Their physical exam and basic laboratory work is usually quite normal.


  • What management changes do I need to make to resolve this situation?

    Make dietary changes slowly. Feed excellent quality feeds. Feed only as much grain as necessary to provide energy for the task the horse will perform.

    Helpful Terms & Topics in HSVGWritten, Reviewed or Shared by Experts in Equine Health

    Author: Doug Thal DVM Dipl. ABVP


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