What Are the Causes of Equine Diarrhea?

Loose stools--diarrhea--in a horse may be a temporary, minor condition but ongoing, severe diarrhea can be a sign of a more serious or infectious illness. Dealing with manure is part of routine daily horse care, so the signs and symptoms of diarrhea rarely go unnoticed for long in a well-kept horse. Any abrupt change in the bowel movements of your horse should be closely monitored. If the symptoms are accompanied by signs of distress or pain, contact your veterinarian.
  1. Salmonellosis

    • Salmonella bacteria live naturally in your horse's intestinal tract and are kept in check by "good" bacteria. When the immune system is compromised or the good bacteria is destroyed (often through antibiotic use) salmonella populations grow and cause severe diarrhea.

    Parasites

    • Parasites can cause diarrhea as can the treatment of parasites (deworming). An ongoing program of sensible deworming should keep populations in check and avoid a massive parasite kill-off that can create severe digestive upset.

    Dietary Causes

    • Sometimes a big belly full of rich forage will cause a bout of diarrhea. If your horse has been stabled and is suddenly faced with a lush growth of pasture grass, it could trigger digestive upsets. Exercise caution when exposing a stabled horse to unlimited pasture--unlimited consumption of new growth grass can cause founder.
      If you are planning to make feed or other dietary changes to your horse's routine, do so slowly. An abrupt change may stress your horse's long--and surprisingly sensitive--digestive tract.

    Stress

    • Trailering, showing or herd changes can stress your horse. Stress isn't always obvious but signs include drooling, agitation and stable vice behaviors.

    Diarrhea in Foals

    • In foals, diarrhea can be serious. If a young horse weakens and is unable to nurse, the dehydration associated with diarrhea will increase quickly. Symptoms include listlessness, failure to nurse, loss of skin elasticity and weakness. An electrolyte solution should be administered immediately. This is a veterinary emergency; don't wait if the foal is not nursing.
      Foal heat diarrhea is not accompanied by the more serious symptoms discussed above. Often this condition will resolve in one to three days. Keep the buttock area clean and apply mineral oil to protect the skin from fecal material.

    Cautions and Treatments

    • Diarrhea can be viral in nature, so if possible, separate sick horses from the rest of the herd. Monitor closely for signs of dehydration and pain.
      Fluids and electrolytes need to be replaced during and after an episode of diarrhea. Anti-diarrheal drugs are not always a good choice; your horse's body is trying to rid itself of something--quickly--and medications may prolong the exposure.