Horse Ulcers: Not the Same for Every Horse

The more horses I treat for ulcers, the more I learn that the same therapies are not equally effective for all horses. This makes sense because not all horses have the same type of ulcers. Horses develop ulcers for different reasons and in different places. It turns out that the topic of treating horse ulcers is more complicated than it might appear at first. So let me see if I can de-mystify the topic a bit.

Where Horse Ulcers Develop
Horse ulcers can occur in multiple places in the horse digestive tract. These include the:

  • upper or non-glandular part of the stomach
  • lower or glandular part of the stomach
  • duodenum (upper part of the small intestine)
  • colon (large intestine)

Horse Ulcers in the Upper (Non-Glandular) Part of the Stomach
Ulcers in the upper part of the stomach, also called gastric ulcers, develop when acid from the lower part of the stomach comes in contact with the lining in the upper part of the stomach. This can happen if a horse doesn’t get enough fiber in his diet. A horse who gets adequate fiber in his diet develops a fibrous “mat” in the upper part of his stomach. This mat prevents the acid from the lower part of the stomach from coming in contact with and irritating the lining of the upper portion of the stomach. Ulcers in this part of the stomach can also develop from any heavy physical exercise that causes the horse to tense his abdominal muscles, forcing acid from the lower stomach into the upper stomach, irritating the stomach lining, even in a horse who has a healthy fibrous mat.

Horse Ulcers in the Lower (Glandular) Part of the Stomach
Horses can also develop ulcers in the lower part of the stomach, the glandular part of the stomach that secretes hydrochloric acid. Another form of gastric ulcer, this kind of ulcer is commonly caused by NSAIDs like Bute or Banamine. These drugs interfere with the stomach’s ability to generate the mucous barrier in the lower stomach that normally protects the stomach lining from the acid. Any horse on high levels of NSAIDs like Bute can quickly develop this kind of ulcer.

Horse Ulcers in the Duodenum
Ulcers can also form in the duodenum, or the upper portion of the small intestine. The basic reason horse ulcers occur in here is indigestion. In a horse, proper digestion is an intricately orchestrated process in which every step has to occur just right. For instance, when the stomach secretes hydrochloric acid, gastrin also needs to be secreted, which in turn releases pancreatic enzymes-all in the right proportions, of course. And that’s only a part of the process. Fortunately, in a healthy horse who is relaxed, this complicated digestive process proceeds smoothly.

It is when the digestive process is interrupted that horses develop ulcers in the duodenum. When a horse is under stress, which triggers a sympathetic nervous system response (also called the fight-or-flight reflex), the digestive process grinds to a halt. For instance, an anxious horse stalled at a show might experience this kind of stress. While he may continue eating, his digestive processes are no longer functioning properly. Instead, his stomach dumps partially digested or undigested food into the duodenum, along with hydrochloric acid. The acid, which is not properly buffered by bile and pancreatic enzymes, irritates the duodenal lining while the undigested food simply rots, causing further irritation. All of this irritation eventually leads to ulcers.

Another cause of duodenal ulcers is a spinal blockage, since the spine provides nerve supply to the digestive organs. Spinal blockages can be caused by injuries or poor-fitting saddles, since the saddle sits right on top of spinal vertebrae responsible for the digestive nerve supply. Adhesions in the abdomen, from sore ovaries or gelding scars, can also lead to duodenal ulcers.

Horse Ulcers in the Colon
As with ulcers that occur in the lower part of the stomach, NSAIDs like Bute can block the production of the mucous that protects the lining of the colon, or large intestine. Without this mucosal lining, volatile fatty acids that are byproducts of the natural fermentation in the digestive process irritate the colon lining, causing ulcers. Also, improper digestion can prevent the small intestine from completely digesting starches. These partially-digested starches are them dumped into the colon, which is meant to digest fiber rather than starches. As a result, the bacterial population that normally lives in the colon and digests fiber dies off, and is replaced by starch-digesting bacteria from the small intestine. While this takes care of digesting starches, the colon can no longer digest fiber. The undigested fibers rot in the colon, producing toxins that irritate the colon wall, ultimately causing ulcers.

Symptoms and Diagnoses of Horse Ulcers
Although it isn’t always easy to diagnose which kind of ulcer a horse might have, the general symptoms of ulcers include:

  • diminished appetite
  • colic
  • frequent pawing
  • weight loss
  • poor performance
  • reluctance to eat grain but ready consumption of hay
  • sore back
  • in foals, colic, a pot-bellied appearance, teeth grinding, and excessive salivation

Specifically, horses with stomach or duodenal ulcers are more likely to express irritation at having the girth tightened. Horses with colonic ulcers are more prone to diarrhea.

Stomach and duodenal ulcers can generally be diagnosed with an endoscope, which is a long flexible tube with a camera and light attached at the end. An endoscope allows a veterinarian to look inside a horse’s stomach and duodenum, but is generally not long enough to reach the lower part of the small intestine or the colon.

An osteopath can diagnose the location of ulcers by the location of spinal blockages. For instance, stomach ulcers are indicated by blockages in the 12th through 14th thoracic vertebrae, while blockages in the 14th through 16th vertebrae indicate duodenal ulcers. Ulcers in the lower small intestine and upper colon cause blockages in the 17th and 18th thoracic vertebrae, and ulcers in the lower colon result in blockages in lumbar vertebrae 1-5.

Confused About Horse Ulcers?
Hopefully this article has provided you with more information about the causes and ways to diagnose the different kinds of horse ulcers. While distinguishing between the different kinds of ulcers may seem confusing at first, my goal is to provide you with the information to more accurately diagnose your horse’s ulcers. Next month I’ll discuss the different ways to treat each kind of ulcer, and ways to prevent horse ulcers from occurring in the future.

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