By Natalie DeFee Mendik
The gelding that kicks the stall wall and acts aggressively toward his neighbors at feeding time. The show horse that’s increasingly more reluctant to perform under saddle. The angsty mare that’s always swishing her tail and grinding her teeth. Many owners observe these quirks in their horses and chalk them up to behavioral issues. But is it truly bad behavior or is it a sign of discomfort? As you’re about to find out, equine gastric ulcer syndrome (EGUS) might be to blame.
Stomach Anatomy Basics
The horse’s stomach has two regions: a nonglandular (squamous mucosa) portion comprising the upper third, and a glandular lower portion. The squamous nonglandular region doesn’t feature the thick, protective mucus and bicarbonate (a pH buffer) layer that the glandular region does, leaving it vulnerable to ulceration from gastric acid.
Frank Andrews, DVM, MS, Dipl. ACVIM, LAIM, LVMA, equine committee professor and director of the Equine Health Studies Program at Louisiana State University’s School of Veterinary Medicine, in Baton Rouge, likens ulcers in the squamous mucosa in horses to gastroesophageal reflux disease (GERD) in humans, in which gastric acid damages the esophageal lining.
“When the horse has an empty stomach or acid in the stomach due to stress, that acid may splash onto the nonglandular mucosa, especially when exercising,” he says, explaining that the hydrochloric acid the cells in the glandular mucosa produce might damage it.
While the stomach’s glandular region enjoys protective mechanisms such as prostaglandins that maintain mucus and blood flow, it’s not immune to ulcer issues, says Andrews. “The glandular mucosa is less susceptible to acid damage, but it is susceptible to stress, dehydration, and dietary issues,” he says.
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