University of Florida (UF) research has shown that any exercise above a walk could force acidic gastric juices up into sensitive areas of the equine stomach, which could be why ulcers develop or worsen in horses in training (affecting more than 80% of performance horses in some studies).

Alfred Merritt, DVM, MS; and Mireia Lorenzo-Figueras, DVM, have found that gastric tension changes during intense exercise can push acidic stomach contents up into the vulnerable upper squamous cell-lined portion of the stomach. The work was done at the Island Whirl Equine Colic Research Laboratory at UF’s College of Veterinary Medicine.

Lorenzo-Figueras and Merritt explored what happens in the stomach of a live, exercising horse by studying UF’s three cannulated research horses–animals with permanent external access to their stomachs. The three Thoroughbreds had Mylar bags (similar to florist balloons) equipped with barostats temporarily inserted in the proximal (upper) parts of their stomachs before treadmill exercise. The barostat maintained constant pressure in the bag, releasing air when the stomach contracted and injecting air into the bag when it relaxed. Because the Mylar bag followed the movements of the gastric wall, changes in the bag’s volume gave an indirect measurement of changes in the stomach’s volume. A computer kept track of the barostat measurements during each exercise test.

The study examined the influence exercise might have on contraction and relaxation of the stomach in horses fed two hours previously, and in those from which feed was withheld for 18 hours before exercise. Over five weeks, the three animals were put through increasingly intense treadmill sessions, culminating in a gallop of nearly two miles (3.2 km) on an uphill slope