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Re: [RC] [AERC-Members] Ulcers - Howard Bramhall

A rider forwarded me this and I'd like to share it with ya'll.


           The Horse
           The Blood-Horse

           Exclusively Equine
           The Horse Source 2003- 2004 Directory

           Article # 4281
           Exercise and Ulcers: Is it the Norm?
                 by: Karen Briggs
                 April 2003

           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.

           It didn't take maximum exertion to produce a notable result. As
soon as each horse moved from a walk to a trot, the volume of air in the bag
decreased rapidly, to the point of almost emptying. The bag remained
deflated when the horses galloped, and didn't regain its original volume
until they came back to a walk. This effect was most dramatic in fasted
horses, but it was observable in the fed horses as well, although the food
in the stomach decreased the initial volume of air in the bag.

           Merritt's team concluded that at any gait faster than a walk,
either the gastric wall was becoming more rigid than normal, or external
pressure was being exerted on the stomach. To investigate the latter, they
inserted a catheter into the abdominal cavity through the right flank to
measure intra-abdominal pressure, while a pressure transducer tracked
intra-gastric pressure. When horses went from a walk to a trot, both
measurements shot up and stayed there for the entire exercise bout, likely
due to tensing of abdominal muscles with the faster gaits.

           External pressure on the stomach during exercise, they
hypothesized, forces the liquid contents of the lower stomach upward,
exposing the more sensitive mucosa of the upper stomach to stomach acids and
inducing ulcerous lesions. On their own, horses rarely exert themselves for
long, so the upper stomach is not naturally exposed to these acids for very
long. Since strenuous exercise can trigger gastro-esophageal reflux
disease--heartburn--in human athletes, the UF findings are an interesting

           Scientists further tested their hypothesis with a pH electrode
inserted into the upper stomach just below the esophageal sphincter to
monitor pH (acidity) during exercise. When horses stood or walked, the pH
remained around 5-6, but as they trotted or cantered, the pH plunged as far
as 1 and remained severely acidic until the horses stopped. This was a
strong indicator that stomach acids were splashing on this sensitive area in
response to strenuous exercise.

           This study shows that gastric ulcers might be more the rule than
the exception when we exercise horses. Ongoing studies should provide more
ways--dietary and pharmaceutical--in which we can normalize the pH or
cushion the equine GI system to minimize damage.

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