Vet Advice: 6 Common Causes of Diarrhea in Horses & How to Treat It

In this post, Jessica Huntington, DVM, from Stephenville, Texas discusses common causes of horse diarrhea and recommendations to treat it. Dr. Huntington takes an integrative approach to the equine athlete by combining traditional veterinary medicine with chiropractic care and acupuncture.

Dealing with horse diarrhea is more than unpleasant and messy—it can be dangerous, leading to serious conditions like dehydration, electrolyte imbalances, weight loss, and even death if left untreated.

As a horse owner or caretaker, understanding the causes and treatment options for diarrhea is crucial for maintaining the health and wellbeing of your equine. In this blog we cover common causes of diarrhea in horses and effective recommendations for prevention, treatment, and management.

Why Does My Horse Have Diarrhea?

Diarrhea is a common gastrointestinal disorder characterized by loose or watery stools. An important function of the equine large colon is to regulate the amount of water absorbed in the body. If you have a horse with diarrhea, it may stem from one of these common instigators of intestinal upset.

1.  Situational Stress

Have you ever noticed when you haul your horse, its manure may be a little loose during trailering or even afterward? This is an example of stress-induced diarrhea. Stress from traveling, prolonged heat, exercise, or performance can trigger loose stool in horses. Typically, you can expect one to two piles before it returns to normal.

2.  Poor Dental Health

Using their teeth to masticate food, horses break down roughage into small pieces to aid in proper digestion. When horses have poor dentition, they're unable to properly chew, leading to longer forage length, which could result in equine diarrhea.

This is a good reason to get a dental checkup. Have your veterinarian examine your horse’s teeth to look for a problematic tooth or abnormality that may be an underlying cause of watery diarrhea.

3.  Internal Parasites

Internal parasites have the ability to invade the colon, attach to the intestinal lining and compromise gut function. This decreases digestive ability and can cause loose manure.

To check for internal parasites, contact your veterinarian for a fecal egg count. This will allow them to identify which internal parasites are present and decide what dewormer is best suited for your horse.

4.  Diet Changes

A rapid change of hay or grain, or feeding too much of either, can bring on diarrhea in horses. When diet changes, so does the bacterium in a horse’s GI tract. If that change is sudden, the gut microbiome can be disrupted.

Diet change should be a gradual process that happens over a period of three to four weeks. During week one, feed your horse three-fourths the amount of regular hay/grain and one-fourth of new hay/grain. At week two, feed one-half the amount of regular hay/grain and one-half of new hay/grain. Starting week three, feed one-fourth of regular hay/grain and three-fourths of new hay/grain. By week four, you can feed entirely the new hay/grain. This slow change will help your equine’s microbiome adjust properly.

5.  Oral Medications

Supplements or medications can also be the culprit of loose manure or diarrhea. For example, a round of antibiotics targeted to kill bad bacteria will also kill good bacteria. This upsets the delicate balance of intestinal flora the GI tract needs to function properly. If you notice loose manure and your horse is or has been on medications recently, it’s best to call your veterinarian for further direction.

6.  Eating Sand

Every day horses ingest incidental amounts of sand from their environment. Small amounts are normal and can usually be easily digested. But if your horse is consuming too much, it can act like sandpaper, irritating and inflaming the gut lining and potentially causing colic and/or diarrhea.

If your equine is fenced in a sandy area, feed out of a large, shallow water tub. By doing so, you are essentially feeding at ground level but not directly in the sand. If you notice your horse outright eating sand, a mineral imbalance might be present and your horse may benefit from a natural mineral supplement.

Horse Diarrhea Treatment