STOMACH ULCERS, An Underestimated Threat Stomach ulcers in horses has, until recently, been a relatively unknown illness, but further research has brought some eye-opening results to the fore. Endurance Horse speaks to Dr Marc Walton to get to the bottom of this. How common are gastric (stomach) ulcers in horses? A recent study in the UK proved how much we underestimate the condition. Around 0.5% of foals were presumed to have ulcers; however, after scoping the stomachs of foals an incidence of 57% was found! The incidence even in pleasure horses was found to be 15%. Studies in competing racehorses have revealed an astounding 60–90%. Most relevant to us, a recent study showed that up to 67% of endurance horses have stomach ulcers. The bottom line: most of our competing endurance horses will have some degree of stomach ulcers! Interestingly, only 40% of horses with gastric ulcers show any symptoms. We may be missing them in a number of horses. How do ulcers develop? Ulcers are easier to understand when you know a little about the anatomy of the horse’s stomach. The stomach’s upper half is a layer of squamous epithelium, similar to our skin. The area has little or no protection, with a high cell repair rate and a thin protective layer being all that separate the cells from acid and enzymes in the stomach. The lower gland-rich half of the stomach has a protective slimy mucus layer and a bicarbonate buffer to bind and neutralise acids before they damage the stomach lining. It makes sense then that ulcers develop mostly in the upper poorly protected regions of the stomach or along the border between the two halves in adult horses. Ulcers develop when there is an imbalance between aggressive (ulcer causing) factors such as acid and digestive enzymes in the stomach vs the protective mechanisms such as mucus (slimy layer), bicarbonate layer, cell regeneration etc. A horse’s saliva also has anti-acid buffering properties. Ulcers are diagnosed and graded by inserting a camera known as an endoscope (“scope”) into the stomach to examine the stomach lining. Ulcers can vary between a grade one (mild redness) to a serious grade four (deep bleeding ulcers). What causes ulcers? Stress. Just like in people, stress is one of the major causes of ulcers in horses. A stressed horse releases the stress hormone cortisol into the system and this has direct effects on the stomach: increasing ulcer causing mechanisms and decreasing the protective mechanisms. Stress such as strenuous training, racing, transport, stabling illness, surgery and weaning can all cause ulcers.