Colonic Ulcers in Horses

Horses that develop long-term difficulty with colon ulcers may have more than one factor operating, as well as more than one cause. It pays to understand what may cause these ulcers and to learn to recognize the symptoms early on.


The symptoms of colonic ulcers are varied (see sidebar) and depend on both the duration and severity of the problem. The most common sign, and the one that is most likely to get your attention, is repeated bouts of abdominal pain.

Rectal examinations typically don’t reveal any helpful findings, and many cases are diagnosed as spasmodic/gas colics or possible mild impactions, and may be tubed with mineral oil, treated for a while with Banamine and recover, only to do it again. Aggressive deworming may be tried to no avail. Gastric ulcers may be suspected, may even be found on endoscopy, but treatment for this doesn’t resolve the problem either. If the horse has progressed to the point where he’s losing enough blood protein (albumin) through the ulcerated areas and this is picked up on a serum chemistry, focus may be directed to the liver, particularly if there is any mild elevation of liver enzymes, but this isn’t the problem either. It may take several vets before you find one that has dealt with the problem, recognizes the symptoms and runs the right tests, or the horse may actually end up in surgery before a diagnosis is made.

How’s his attitude’ Depression could be a symptom of a colonic ulcer. Banamine may be part of the treatment.


Directly examining the horse’s stomach is a lot simpler matter than getting a look at his colon. The large and small colon combined are about 25 feet long. Physical examination and rectal examination may not reveal much more than some increased gas. Short of opening the horse surgically to get a look and do biopsies, diagnostic techniques were largely limited until recently. In 2003, clinicians from the North Carolina State College of Veterinary Medicine published information on using ultrasound to diagnose right dorsal colitis. Because the colon lies close to the body surface, it is easily imaged using ultrasound and a thickened, inflamed wall can be seen. Another test is intravenous administration of radioactively labeled albumin. The manure is then tested to see how much passes into the intestinal tract.


Sporadic colonic ulcers related to drug use or parasties probably occur all the time and heal on their own without us ever realizing they were there. Concern about colonic ulcers rose to a brief fever pitch in 2005 when a well-publicized article reported that postmortem examinations of 454 horses found colonic ulcers in 45% of nonperformance horses and 65% of performance horses.

However, these were examinations done on horses that had been killed at a Texas slaughterhouse. Their histories were unknown, including use/performance. Horses that are performing well typically don’t end up in slaughter auctions. Since lameness is a common cause of poor performance, and of horses going to auction, there’s a pretty high likelihood there was use of bute both before the decision was made to dispose of the horse, and on the day of sale in hopes the horse might look good enough to bring a better price. Those findings aren’t at all representative of horses in general.


Most vets agree the cornerstone of treatment for the most common cause of colonic ulcers, right dorsal colitis, is complete avoidance of NSAIDs, especially bute, and feeding a complete, pelleted feed without hay. A similar approach of a low-residue diet is also often used in human colonic disorders. This diet is higher in digestible fiber, lower in indigestible fiber that may be irritating to the bowel. These meals are often fed wet, which further improves the ease of digestion. For horses with inflammatory bowel disease who may have allergies/intolerances to allergenic feed ingredients like soy, corn, alfalfa or wheat products, this may not be enough. Starting with a base diet of pelleted/cubed grass hay from a consistent source, individual items can be added back in once the horse is stabilized.

A diet generous in easily fermented fiber does more than just mechanically protect the bowel and limit exposure to potential allergens. The lining of the bowel receives much of it is nutrition in the form of volatile fatty acids produced by the fermentation of fiber. Provision of readily fermented fiber also encourages the proliferation of generous numbers of beneficial microbacteria in the gut, which in turn crowds out any potentially harmful organisms.


Along these same lines, provision of a potent prebiotic such as Ration Plus (, 801-533-9208) and/or high-dose probiotic is a good support measure (look for an article on probiotics in an upcoming issue).

A variety of other nutritional supports may also be tried, including:

• The amino acid glutamine, or its precursor, N-acetyl cysteine. These are antioxidant nutrients, helpful in cell culture models but unproven in live animals or humans.

• Sucralfate. This is a sulfated complex carbohydrate that escapes digestion by the small intestinal enzymes. It binds to the surface of ulcerated areas, protecting them. It is helpful in human small intestinal ulcers (but not equine gastric ulcers) and is sometimes recommended for colonic ulcers. However, it is unknown if sucralfate can escape fermentation by the organisms in the a horse’s colon.

• Flaxseed/flaxseed oil: The omega-3 essential fatty acids high in flax oil (and fresh grass) are well known to have anti-inflammatory effects in all species, while the omega-6 fatty acids predominating in all other vegetable and seed oils promote it.

There is some experimental work in other species to suggest that omega-3 fatty acids can speed healing of colon lesions, particularly in combination with olive oil (high in oleic acid). If the horse does not have access to fresh grass, flax oil supplementation is reasonable.

• Aloe vera. The aloe vera plant has well-documented anti-inflammatory effects and has documented benefit in bowel inflammation in human patients and experimental animals. Although no formal equine studies are available, we know of horses with right dorsal colitis that have benefitted from aloe.

• Bovine colostrum. The colostrum of all species contains a broad spectrum of immunologically active substances such as preformed antibodies that bind to pathogens in the gut, and immune system regulating peptides. Colostrum has been useful in some small trials in human inflammatory bowel disease, and we’ve seen it work extremely well in at least one horse.

• Selenium. Although no one has looked at this in horses, studies in people with multiple types of colonic inflammation have consistently shown low selenium status. Selenium and vitamin E treatment of experimental animals with induced colitis has been shown to be very helpful in minimizing inflammation.

Since selenium (and vitamin E) deficiency is one of the most widespread mineral deficiencies in horses, ensuring adequate intake of this key mineral would be wise. For horses with disease that also involves their small intestine, selenium injections by your vet would be more effective.

Although they may not have been the cause of the problem, the last thing a horse with colonic ulcers needs is irritation from parasites. A daily pyrantel tartrate dewormer will at least keep the horse tapeworm free, although you will likely be advised to supplement this with paste deworming using other drugs because of possible resistance problems.


When the correct internal conditions are achieved, the intestinal lining has an excellent capacity to heal.

The process of getting inflammation under control and complete healing will usually take about three months, although colic symptoms will be reduced or eliminated greatly long before that. A consistent feeding schedule, avoiding dietary changes and avoidance of stress are all important.

Prognosis for full recovery once you have a diet they can tolerate is very good. Horses with inflammatory bowel disease that can’t be weaned off steroids have a poor prognosis. The only other thing that may complicate the picture is the formation of strictures???narrowed, scarred areas???in the bowel in longstanding cases.

Severely strictured areas can be removed surgically and the bowel reconnected, although strictures may form at the sites of surgery as well.

Strictures predispose to both pain from altered motility and backups or actual impactions at narrowed areas. Horses with strictures may have to be managed by a diet of pelleted feed/hay, fed as high liquid mashes to keep contents moving along freely.

Article by Eleanor Kellon, VMD, our Veterinary Editor.

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