The Different Types of Ulcers in the Equine GI Tract

Gastric ulcers are sores that form on the stomach lining in the horse. Research has estimated that the prevalence may be up to 90% in some demographics. Working horses tend to be more at risk of developing this disease due to the intensive management they are often exposed to.

When equine gastric ulcers are discussed, it is not frequently clarified exactly which type the horse has which is problematic as prevention and treatment strategies differ depending on the type of ulcer. With more research being published on the disease, it has become apparent that there are critical differences between the various types which need to be taken into consideration when curating a treatment plan.

In the stomach, the ulcers are classified depending on their location. Equine squamous gastric ulcers (ESGUs) are ulcers that are in the non-glandular, or squamous portion of the stomach. The non-glandular portion of the stomach is the upper region.

Equine glandular gastric ulcers (EGGUs) are ulcers that are in the glandular portion of the stomach. This is the lower region where hydrochloric acid is continuously secreted. When we refer to equine gastric ulcer syndrome (EGUS) this encompasses both the squamous and glandular. Now, there can also be ulcers that develop in the hindgut of the horse. These ulcers are referred to as colonic ulcers. They are less common than gastric ulcers, but still have a high prevalence.

A 2005 necropsy study evaluated over 500 horses, the first group of horses examined showed that 55% were found to have gastric ulcers, and 44% had colonic ulcers. The second group that was evaluated was performance horses, and in this group 87% had gastric ulcers and 63% had colonic ulcers.

The risk factors for ulcer development differ depending on the location in the gastrointestinal tract. If we start with the squamous ulcers (in the top portion of the stomach), it is known that the risk for development increases with the intensity of management. This includes factors such as inadequate forage access, large carbohydrate meals and increased workload. The top portion of the stomach (the squamous mucosa) does not have the same protective mechanisms that the glandular portion has. Therefore, we need to limit the acid exposure. The changes in management factors that we see in working horses increases the acid exposure and increases the risk of ulcer development. They are essentially a chemical burn on the unprotected mucosa in the stomach.

If we shift our focus to the glandular ulcers, which are in the lower portion of the stomach, the risk factors change. Research has not determined that the development of glandular ulcers is directly related to management intensity. For example, this type of ulcer tends to be more prevalent in Warmblood sport horses than in endurance or racehorses (which have a higher prevalence of the squamous ulcers). We do not have the science to fully elucidate the causes of glandular ulcers in horses. As of right now, it is thought that the development of glandular ulcers is related to behavioural stress and the lack of rest days for exercising horses.

Treatment also differs between squamous and glandular stomach ulcers. Omeprazole is used for squamous disease with a high rate of success. For glandular disease, often a combination of omeprazole, sucralfate, and misoprostol are used. If you suspect that your horse has gastric ulcers, you should contact your veterinarian regarding medical treatment.

As a nutritionist, I am most frequently asked about prevention, because of course if you suspect ulcers, you need medical treatment. Once your veterinarian has evaluated the type of ulcer and prescribed treatment, we can chat about management and dietary changes to prevent reoccurrence.

When creating a plan to prevent the recurrence of squamous gastric ulcers, the focus is always on adequate forage, reducing carbohydrates and the timing of exercise – for example, not working the horse on an empty stomach. As discussed, glandular ulcers differ from squamous, therefore, for prevention of this type of gastric ulcer there is a focus on environmental optimization, this refers to having horses housed together and in an environment that allows for free movement and trickle feeding to reduce stress. The implementation of adequate rest days is also thought to be an important factor in prevention.

When it comes to colonic ulcers, those that are not in the stomach, but instead in the hindgut of the horse, they are thought to be caused by stress, the use of non-steroidal anti-inflammatory medications, a high parasite load and/or hindgut acidosis. Both squamous and glandular gastric ulcers can be viewed via gastroscopy. However, these scopes are unable to reach the hindgut of the horse.

Therefore, the diagnosis of colonic ulcers, also referred to as right dorsal colitis (RDC) relies on clinical symptoms, blood work, and abdominal ultrasound. Some of the common symptoms are recurring colic, reduced appetite, poor haircoat health, etc. Of course, these symptoms are not specific and can be due to a variety of health issues which is why it is critical that you contact your veterinarian immediately for any health concerns. The treatment of colonic ulcers is often a combination of medical management, nutritional changes, and alteration in management.

Overall, equine gastric ulcers and colonic ulcers are unfortunately all too common. However, if your horse has had ulcers, or you suspect that they might have ulcers – understanding the risk factors and the type of ulcer your veterinarian diagnoses can make a difference in how prevention is approached.

By: Madeline Boast, MSc. Equine Nutrition

References:

Andrews, F. M. (2009). Overview of gastric and colonic ulcers. Advances in Equine Nutrition IV, 347.

Pellegrini, F. L. (2005). Results of a large-scale necroscopic study of equine colonic ulcers. Journal of equine veterinary science, 25(3), 113-117.

Rendle, D., Bowen, M., Brazil, T., Conwell, R., Hallowell, G., Hepburn, R., … & Sykes, B. (2018). Recommendations for the management of equine glandular gastric disease. UK-Vet Equine, 2(Sup1), 2-11.

Sykes, B. W., Bowen, M., Habershon‐Butcher, J. L., Green, M., & Hallowell, G. D. (2019). Management factors and clinical implications of glandular and squamous gastric disease in horses. Journal of veterinary internal medicine, 33(1), 233-240.

Vokes, J., Lovett, A., & Sykes, B. (2023). Equine gastric ulcer syndrome: an update on current knowledge. Animals, 13(7), 1261.