Research indicates that in the world of sport horses, 40 to 90% of the population suffers from stomach ulcers. But why are stomach ulcers so common in sport horses? Let’s delve deeper into this prevalent issue and explore how we can understand and potentially prevent it.

What are stomach ulcers?

To better understand why stomach ulcers occur in horses, we first need to grasp the functioning of the equine stomach. A horse’s stomach is divided into two parts: the squamous region (upper part), which lacks glands that produce stomach acid, and the glandular region (lower half), where hydrochloric acid (HCl) is produced. The squamous region consists of cells that are not resistant to stomach acid, so it is vital to prevent reflux of stomach acid into this area. The glandular region is typically protected against the produced stomach acid and its associated lower pH.

Horses have evolved with a diet rich in fiber and low in starch and sugars. Additionally, the eating pattern of horses is crucial because their digestive system is adapted to a feed intake spread over 24 hours. Consequently, horses continuously produce stomach acid, even when not eating. Roughage, saliva, and water play a key role in diluting and buffering this stomach acid.

How do stomach ulcers appear?

Unlike stomach acid, saliva is only produced during chewing. Saliva is essential for diluting (and buffering) stomach acid and is maintained with natural foraging behaviour. When access to roughage or water is restricted, the dilution/buffering of stomach acid may not occur effectively, increasing the risk of stomach ulcers in the squamous region of the stomach.

With unrestricted access to roughage, the pH in the squamous region varies between 5 and 7, while in the glandular region, it ranges between 2 and 3. These pH values not only differ between the stomach sections but also throughout the day and diets. A decrease in roughage intake can lower the pH value in the squamous region to 4 or lower. When this occurs, the risk of stomach ulcers in the squamous region increases. Additionally, stomach ulcers can also occur in the glandular region.

Fun fact: the general term for stomach ulcers is Equine Gastric Ulcer Syndrome (EGUS). When the stomach ulcer is in the squamous area of the stomach, it can be classified as Equine Squamous Gastric Disease (ESGD). If the ulcer is in the glandular area, it can be classified as Equine Glandular Gastric Disease (EGGD).

What are the symptoms of stomach ulcers?

While not all horses show symptoms, signs of stomach ulcers may include:

• Colic
• Weight loss
• Changes in appetite
• Diarrhea
• Flehmen response
• Teeth grinding
• Changes in behavior

If you suspect your horse has a stomach ulcer, consult a veterinarian for a diagnosis.

Risk factors and prevention of stomach ulcers in the squamous region

Risk factors for ESGD (Equine Squamous Gastric Disease, stomach ulcers in the squamous region) in horses may vary, but in the literature, roughage, training, and the level of non-structural carbohydrates in the diet are described.

Roughage

It has been shown that a shortage of roughage can lead to an increased risk of stomach ulcers. To prevent this, it is important to offer horses unlimited roughage or prevent long periods (more than 4 hours) without roughage.

Roughage has several benefits such as stimulating saliva, diluting stomach acid due to its large volume, and forming a protective “mat” in the stomach against reflux of stomach acid.

Training

Training can also influence the risk of stomach ulcers in horses. Intensive training can expose the squamous region to stomach acid due to gastric contractions. Pre-training feeding of roughage appears to have a buffering effect and may reduce the risk.

Non-structural carbohydrate content of the diet

The level of non-structural carbohydrates, such as sugar and starch, in the diet may also play a role in the development of stomach ulcers. It is recommended to feed horses a diet based on roughage and any supplementary feed with a low sugar and starch content. When feeding concentrates, they can be mixed with a roughage mix such as Hartog Digest to reduce the impact of concentrates on the stomach. Additionally, it is advisable to avoid feeding large amounts of concentrates when more energy is required or when the horse needs to gain weight. In these cases, opt for fiber-based products and/or vegetable oil.

Risk factors and prevention of stomach ulcers in the glandular region

For EGGD (Equine Glandular Gastric Disease, stomach ulcers in the glandular region), there are fewer clear risk factors. Several studies have been conducted, but to date, no relationship has been found between the diet and EGGD. Normally, the glandular region is protected against stomach acid, thereby preventing stomach ulcers in this part of the stomach. It appears that a loss of this protection is the cause of EGGD. Further research is needed to better understand the nutrition-related risks and prevention of EGGD.

Conclusion and further information

This article provides a glimpse into the topic of stomach ulcers in horses. However, if you want to learn more about this topic, various experts in this field have compiled their expertise in a consensus statement on the current knowledge of stomach ulcers, namely: “Equine Gastric Ulcer Syndrome: An Update on Current Knowledge”. The information in this article is derived from this statement.

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