by Brittany Silvers

Is the Microbiome Related to Ulcers in Horses?

Is the Microbiome Related to Ulcers in Horses?

Did you know that up to 65% of performance horses and even many non-performance horses are affected by ulcers? (1,2). 

These can be extremely painful for the horse and can result in poor performance and low quality of life. Equine ulcers can occur in the stomach (gastric ulcers, i.e. the ones you usually hear about), as well as in the large intestine (hindgut ulcers).

Equine Gastric Ulcer Syndrome

Horses have a unique stomach, which is important to understand:

  • The equine stomach is very small, comprising only 10% of the digestive tract, meaning it has a low capacity. The stomach of the horse is adapted for the grazing behavior of horses, which results in continuous hydrochloric acid production all day long. 
  • It contains two distinct regions: the squamous region (or non-glandular region) is found on the top part of the stomach near the esophagus, and the glandular region which is closer to the small intestine. 
  • The glandular portion of the stomach can produce a buffer to protect the stomach lining against gastric acid, while the non-glandular region is more vulnerable to damage by stomach acid. The line (yes, there is an actual physical line) where these two mucosa types join is called the margo plicatus

When horses graze all day, as they are physically adapted to do, they have a near constant supply of forage in the stomach, accompanied by saliva which contains an acid buffer. This helps keep the pH of the stomach in the proper range. 

However, when we feed large grain meals and leave horses with long periods of fasting, the lack of buffer and increase in acid secretion can decrease the pH of the stomach, leading to gastric ulcer formation.

Signs of Ulcers in Horses 

Now, I didn’t throw in complicated words just for fun- the margo plicatus is an important landmark in the stomach, as it is where horse ulcers tend to occur. When low pH (high acidity) fluids from the glandular region of the stomach come into contact with the vulnerable non-glandular region at this junction, damage occurs in the form of gastric ulcer syndrome. 

This contact tends to be exacerbated when horses exercise, especially on a completely empty stomach, because acid splashes up past the margo plicatus as the stomach contracts during movement. 

The only way to officially diagnose the presence of gastric ulcers is through the use of an endoscope in the stomach, however common symptoms include weight loss, loss of appetite, your horse becoming “girthy” or “cinchy”, attitude changes, as well as colic symptoms (1).

The Equine Hindgut

When many horse owners hear the word “ulcers,” thoughts likely go immediately to the stomach, however, hindgut ulcers can also be common in horses. These ulcers tend to occur in either the equine cecum or the colon, where a majority of forage fermentation occurs. 

While we do not know as much about hindgut ulcers yet as we do about gastric ulcers, it seems that the leading cause for issues in the cecum and colon is the underfeeding of forage and overfeeding of grain concentrates.

When too much grain is fed at one time, the stomach and small intestine cannot properly digest all of it, so some will pass to the large intestine undigested. When this starch is fermented, the pH in the hindgut will drop, killing the fiber-fermenting good bacteria, causing more starch-fermenting bacteria to grow and the pH to drop more, and then... you get the picture. 

Hindgut ulcers are far more difficult to diagnose and require a holistic approach: ultrasound in combination with observation of symptoms and blood work can be utilized. Common symptoms include weight loss, poor coat condition, chronic colic and diarrhea. 

These symptoms are similar to those of gastric ulcers which may make them hard to distinguish from one another, but it’s not uncommon for both types to occur simultaneously. (2)

How do you treat ulcers in horses?

Currently, the only proven drug for ulcer treatment for horses is omeprazole. This is found in both Gastrogard and Ulcergard, however Gastrogard is for the treatment of ulcers while Ulcergard is for prevention. (3) The treatment for hindgut ulcers is far more complicated (2). 

I am probably starting to sound like a broken record when I say: prevention is key!

Like many digestive problems in the horse, ulcers are primarily man-made and can mostly be prevented by proper management. 

Avoid feeding large meals with long amounts of time in between, try to feed as many small meals a day as you can, and provide free choice access to forage such as grass or hay to help neutralize the pH in the gastrointestinal tract. 

Probiotics for Prevention

A piece of your prevention plan should include providing your horse with probiotics, which can assist in establishing a healthy microbial population. The good microbes in probiotics will help maintain the proper pH in the horse’s gut and help avoid ulcers. 

Probiotics will also help to combat any shifts in the equine microbiome that may be caused by stressful situations such as trailer rides, long periods of stall confinement, or movement to a new facility, which can help minimize the likelihood of ulcers due to stress.

If you suspect that your horse is dealing with ulcers, be sure to consult with your veterinarian to establish the best treatment and health program for your individual horse. Maintaining a happy gut means owning a happy horse! 

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