MSD Manual

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Professional Version

Free Fecal Water Syndrome in Horses


Allison J. Stewart

, BVSc (Hons), PhD, DACVIM-LAIM, DACVECC, School of Veterinary Science, University of Queensland

Reviewed/Revised Oct 2022

Free Fecal Water syndrome is a condition in which horses produce normal manure, but before, during, or after defecation watery feces runs from the anus.

Although often concerning for horse owners, it is not associated with infectious causes of diarrhea. However, the watery feces can run down the hind legs and cause skin irritation. Smearing the inside of the legs with petroleum jelly or zinc oxide cream can protect the skin.

There are anecdotal reports that suggest the cause may be due to a range of problems such as poor dentition, stressful situations, parasites, or inflammatory bowel disease.

Some horses respond to dietary management with free-choice hay, and others respond to diets consisting of chaff or chopped hay or hay pellets. Some horses improve with the addition of psyllium husk or table salt (0.5 to 2 tablespoons per day).

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