Diarrhea in the Adult Horse

(Photo by Lauren Lamb)

By Lauren Lamb

The equine digestive tract is a complex and fragile system that is easily disrupted. Colic is the most common outcome of a digestive tract upset in a horse; however, diarrhea is a close second. Colitis (inflammation in the colon) is another term used to describe a horse with diarrhea. Diarrhea in a horse is caused by a lack of water absorption in the large colon, which can result in a loss of 10 gallons of water and electrolytes daily. There are numerous potential causes of diarrhea. They can be grouped into the following categories:

-Infectious diseases such as Salmonella, Clostridium or Potomac Horse Fever

-Altered intestinal flora (microbes in the colon). This can be seen in horses that are on antibiotics or exposed to toxins. This type of diarrhea more times than not leads to infectious diarrhea.

-Non-infectious diarrhea

  • Changes in diet (lush pastures, rich feed, excessive carbohydrates)
  • Inflammatory bowel disease
  • Neoplasia
  • Sand in the colon

Horses with non-infectious diarrhea can have a transient diarrhea that will resolve in a couple of days with minimal clinical signs, or they can have a chronic diarrhea with minimal to mild clinical signs. Horses with diarrhea secondary to an infectious disease will have a more severe case of diarrhea that could potentially become life threatening if not addressed properly.

Clinical signs of infectious diarrhea may be one of the most important factors to consider when deciphering between infectious and non-infectious diarrhea. Horse with infectious diarrhea will develop diarrhea rapidly. Within hours they go from having normal manure to straight water. They are frequently depressed, lethargic, colicky, not eating, sweating, have cold extremities and their heart rate and respiratory rate will be elevated.

Learn more in the June issue of OKFR!