Skip to main content

Dealing With Diarrhea

The gums are pink and they glisten with moisture, two signs of good hydration.

The gums are pink and they glisten with moisture, two signs of good hydration.

Diarrhea can be an extremely frustrating problem for horse owners to deal with. In the warm weather it is complicated by fly attention and in the cool weather it is more difficult to keep your horse clean and dry. Chronic diarrhea drains nutrients from your horse and acute diarrhea can dehydrate your horse.

No matter what has caused your horse's diarrhea, there are some basic care practices you can follow:

Clean your horse's butt and hind legs thoroughly.

Braid the tail to keep long hairs out of any fluid diarrhea.

To prevent irritated skin, apply diaper-rash ointment or petroleum jelly to the area.

First Steps

It helps to cut back on your horse's grain. Keep feeding hay/roughage, but if you're feeding rich alfalfa, consider a switch to a mostly grass hay.

it's extremely important to make sure your horse has plenty of fresh water to combat any dehydration. Scrub water buckets and tubs daily and refill.

Any horse with diarrhea should be kept separate both for contagious disease reasons (see sidebar on page 8) and so you can monitor just how much fluid your horse is taking in.

Check any horse with diarrhea for signs of dehydration two or three times a day, more if it's a foal. A simple way to check is to pinch the skin at the neck or gently pinch the skin of the eyelid. In a well-hydrated horse, the skin will quickly flatten out. With a dehydrated horse, the skin will stay puckered up and then flatten relatively gradually.

Look at your horse's gums. Healthy gums are pink and look and feel moist. If you touch the gums, the area should whiten and then almost immediately pink right back up. This is called CRT or capillary refill time. In a healthy, well-hydrated horse, this will be two seconds or less.

For mild diarrhea, you can add Pepto Bismol (bismuth subsalicylate) to your horse's daily ration. Give this at about five ounces (10 tablespoons) at a time, but don't overdo it.

Remove diarrhea stains quickly to prevent hair loss. Coating the area with petroleum jelly will help protect it.

Remove diarrhea stains quickly to prevent hair loss. Coating the area with petroleum jelly will help protect it.

This is most easily given via a plastic dosing syringe. Extrapolate from the human dose to fit your horse's size. This can be given three to four times a day. Pepto can bind a horse, especially a foal, so be sure you are monitoring the horse's manure output.

That means, since you don't want to risk impaction, don't dose your horse and then throw him out into a 20-acre pasture where You'll have no idea what his manure looks like. If Pepto does help, gradually wean your horse off it over the course of a couple of days.


(di-tri-octahedral smectite) is a commercial clay-type product that can help with some diarrhea cases by not only firming up manure but also binding to some of the toxins produced by bacteria such as the various clostridia (, 800-553-2400). However, this should be used under the guidance of your veterinarian. Activated charcoal may also be prescribed to help absorb toxins.


the supplement for sand colic, is also helpful with diarrhea and loose manure. For temporary relief, feed psyllium according to label instructions for five days at a time. it's counterproductive to feed it constantly, as your horse will adjust and adapt to psyllium?s increased fiber over time. For a quick fix, however, it usually helps thicken things up.

In human medicine, much is made of the use of probiotics for treating diarrhea cases. These may help for your horse. We've seen Ration Plus (, 800-728-4667) help many horses. However, there have not been many hard core studies in this area.

You can also try Saccharomyces boulardii or use live culture yogurt (not all grocery-store products are live culture). These items should be kept refrigerated until used.

The goal here is to ?seed? some good bacteria into the gut to lower the numbers of the toxic bacteria that may be behind the diarrhea. Your veterinarian may dispense these items or recommend you purchase them if your horse needs a course of antibiotics (more on antibiotics, below).

A change to a lush pasture can cause diarrhea.

A change to a lush pasture can cause diarrhea.

Even if you feel you're keeping your horse's diarrhea under control and getting his gut flora back to normal, consider getting a fecal sample checked. Many cases of diarrhea in horses are parasite-related. If you take a sample in, bring your deworming schedule records, too, so your vet can make recommendations for a treatment.

Common Causes

With foals involved, you need to look at Lawsonia, Clostridia, Rhodococcus and Rotavirus. Your veterinarian will need samples (possibly both blood and manure) to verify these problems. Don?t begrudge doing the samples. The expense is worth it to determine the cause.

If it's parasites you now need to adjust your deworming protocol. Parasite loads can affect young foals as well as adult horses. Deworming is often a first step in treating many diarrheas, especially if small strongyles are suspected.

If Rotavirus shows up, you know you need to vaccinate. Rotaviral vaccinations are not part of the AAEP core vaccines but if your farm has a problem, it needs to be added to your schedule. Weigh the value of one foal against the cost of testing and the answer should be clear.

Remember to think about foal-heat diarrhea with foals. When the mare they are nursing goes into heat after foaling, many foals will have loose manure.

Don?t forget diet. Excess grain, sudden exposure to lush pasture and recent abrupt changes in diet can all cause diarrhea. Simply cutting back on pasture time may firm things up. Gradually increasing the time your horse is out works well.

Many antibiotics can cause bacteria due to a shift in the bacteria in your horse's gut. If your horse needs antibiotics, ask your veterinarian if it makes sense to add a probiotic to his treatment regimen. Nonsteroidal anti-inflammatory medications may also cause diarrhea.

Potomac horse fever is another serious cause of diarrhea. If you have one horse in the barn diagnosed with Potomac horse fever, you need to consider why and how that individual was exposed. When a horse shows up with diarrhea in the summer, especially if that horse lives near a body of water, we recommend turning off all barn lights at night. The lights attract the insects that are involved in the spread of this illness.

Bottom Line

Diarrhea can be serious or a mild blip in your horse's health. Begin early treatment with the suggestions here, but any sign of worsening or dehydration requires veterinary involvement.

Article by Deb Eldredge, DVM, Contributing Veterinary Editor, with the assistance of Dr. Julie Wilson, of Turner-Wilson Equine Consulting near Minneapolis, Minn.