Diarrhea in Horses

Horse manure beside shovel.
Horse manure should be firm and not runny or wet. Image Credit:tirc83/E+ /Getty Images

Runny manure is not normal. Diarrhea is a sign that something is wrong with your horse's health. One problem horses owners often ask is ‘what should I do about my horse’s diarrhea’. And the advice experienced horse owners and veterinarians give is usually not the advice they want to get. Unless the problem clears up within a day,  if your horse has diarrhea, you should call your veterinarian. No one likes veterinarian bills or the inconvenience of waiting for the vet to arrive. But, horses can very quickly become dehydrated when they have diarrhea, and that can cause laminitis, kidney failure, and in extreme cases, death. The underlying causes of diarrhea can be caused by serious problems.

What is Diarrhea?

Diarrhea is a symptom, not an illness in itself and often indicates that something is awry with the horse’s digestive system. Usually, a horse’s manure is a pile of nicely formed, round-ish ‘buns’ or ‘road apples’. However, if the horse’s digestive system rushes its contents through too quickly, the manure can range from slightly sloppy, to loose and very watery. In severe cases, the loose manure may exit forcibly, and end up covering stall walls and anything else in the way. Diarrhea can last a day or two, and you may never find the reason it occurred. But in some cases, it can become chronic requiring ongoing treatment and vigilance.

What Causes Diarrhea?

There are many reasons horses get diarrhea. While most episodes of diarrhea are not a huge problem, diarrhea can also be an indication of a serious life-threatening illness. Here is a list of just some of the things that cause diarrhea.

  • Nervousness caused by being in a trailer or attending an event. this usually resolves as soon as the horse returns home.
  • Change of feed- either new feed the horse is not used to or overfeeding
  • Change of stable
  • Food sensitivity or allergy
  • Spoiled Feed
  • Antibiotics
  • De-worming medication
  • Parasite load
  • Salmonella
  • Equine Gastric Ulcer Syndrome or EGUS
  • Sand Enteropathy
  • Potomac horse fever
  • NSAIDs (including Butazone)
  • Colitis
  • Poisoning such as slaframine poisoning
  • Cancer
  • Rotavirus

When Should You Treat Diarrhea on Your Own?

If your horse has diarrhea, you need to determine how severe it is. You may know that your horse gets nervous when the farrier comes, in the trailer or at horse shows. In these cases, runny manure probably isn’t a sign of illness, and once the stress is over, things will return to normal. Do, however, make sure your horse is eating and drinking normally otherwise. If after 24 hours, the diarrhea is not gone, it is time to call the vet.

How Do You Know It’s Time to Call the Vet?

If the diarrhea isn’t caused by something obvious that you know will pass, then it’s time to discover other possible causes. Start to worry if along with diarrhea, your horse also shows any of the following symptoms:

  • Extremely watery manure
  • Blood or mucus in the manure
  • Foul smelling manure (beyond the normal manure smell)
  • Diarrhea lasts more than twenty-four hours
  • “Projectile pooping” 
  • Other colic symptoms
  • A change in TPRs that suggest the horse has a fever
  • Lethargy – low energy
  • Signs of weight loss or other health problems before diarrhea started
  • There are signs of dehydration (do a skin pinch or capillary refill test)

Call your veterinarian, who will help you find out what is causing diarrhea and start your horse on the appropriate treatment. The vet will probably take a fecal sample to help determine the cause of the problem, and suggest keeping the horse away from other horses, should the problem turn out to be contagious. The vet may also give the horse medication to ease any discomfort and to help slow the gut down like Kaopectate or psyllium fiber. Probiotics and other gut-balancing supplements may be given on the advice of the veterinarian. Depending on what caused ​diarrhea your horse might be given antibiotics or other drugs. 

Preventing Diarrhea

Avoiding diarrhea is very like avoiding colic. Avoid rapid changes in feeds. Introduce horses to lush pastures gradually. Keep feeds such as grains and concentrated locked down so horses that might get loose can’t help themselves. De-worm your horse regularly. Vaccinate your horse with the core vaccines and any that are appropriate for your area.