Gastric Ulcer Research

Gastric ulcer disease is a serious health problem in horses resulting in colic, poor performance, and pain. The term equine gastric ulcer syndrome (EGUS) describes erosions and ulcerations occurring in the lower portion of the esophagus, non-glandular and glandular stomach, and proximal duodenum (beginning of the small intestine) of horses.

EGUS is caused by many factors, including stomach anatomy, exercise, restricted feed intake, diet, environmental stressors (such as transport), and the use of non-steroidal anti-inflammatory agents (NSAIDs). Treatment is expensive, and current medications must be administered over several weeks to months. Some horses with EGUS are resistant to current treatments and might benefit from a change in diet.

Performance horses that are fed high- concentrate diets (grain) are more likely to develop gastric ulcers than horses at pasture. The sugars in grains are fermented by resident stomach bacteria (Lactobacillus and Streptococcus spp.), producing acid byproducts called volatile fatty acids (VFAs). In the presence of normal stomach hydrochloric acid, these VFAs cause injury and ulceration when absorbed through the stomach wall.

The non-glandular squamous region of the horse's stomach, located in the inner one-third of the stomach, is covered by "tender" tissue and has minimal protection against acid injury. Stomach acids and VFAs have been implicated in causing gastric ulcers.

Performance horses commonly eat diets high in fermentable grains. Our research at the University of Tennessee College of Veterinary Medicine has focused on soluble carbohydrates (sugars in grain), the production of VFAs, and their roles in causing ulcers.

Jennifer Nadeau, MS, PhD, a graduate student in our laboratory and an assistant professor of animal sciences at the University of Connecticut, initially showed that horses with stomach ulcers fed bromegrass hay and alfalfa hay/grain diets had lower gastric juice pH (more acid) and higher VFAs than horses without stomach ulcers. Additionally, the high calcium and protein in an alfalfa hay diet reduced the number and severity of the gastric ulcers, which means it might protect the stomach lining from acid damage.

Recently, our group showed that VFAs (especially acetic acid, known as vinegar) produced as byproducts of bacterial fermentation of carbohydrates damaged the stomach lining and caused the gastric ulcers after only two hours.

Our group showed damaging concentrations of acetic acid could be achieved when grain was fed at greater than 0.6 kg (1.3 pounds) per 100 kg (220 pounds) of body weight (approximately six pounds of grain for the average horse).

From this research, our group concluded that horses needing extra grain should be fed ¡Ü 0.5 kg (1.1 pounds) per 100 kg (220 pounds) of body weight of concentrates every six to eight hours to decrease the risk of gastric ulcers. (Don't feed more than five pounds of grain per feeding.)

Additionally, feeding alfalfa hay, either in part or totally (because of its high calcium and protein), can buffer the stomach, acting as a dietary antacid and reducing the effect on the stomach lining.

This is preliminary research, and further studies are required to determine the exact quantity of grain needed in horses to meet nutritional needs, while minimizing the effects of acids on the stomach lining.

Current research, in collaboration with Rafat Al Jassim, PhD, lecturer at the University of Queensland in Australia, is focusing on identifying the bacteria present in stomach contents and the effect of lactic acid, another byproduct of bacterial fermentation of grain, on the stomach lining. Results of this and other studies could lead to the development of anti-ulcerogenic diets or feed additives that could prevent EGUS in horses at risk.

Completed results of this research were published in the August 2000, April 2003, and an upcoming issue (2006), of the American Journal of Veterinary Research and Reproduction Nutrition Development. Researchers include Jassim, Nadeau, Benjamin R. Buchanan, DVM, Dipl. ACVIM, Sionagh H. Smith, DVM, PhD, Dipl. ACVP, Sarah B. Elliott, BS, and Arnold M. Saxton, PhD.

This research was made possible by grants from the Grayson-Jockey Club Research Foundation, Comparative Gastroenterology Society, University of Tennessee Centers of Excellence in Livestock Diseases, and Human Health and Rural Industries Research and Development Corporation.

About the Author

Frank M. Andrews, DVM, MS, Dipl. ACVIM

Frank M. Andrews, DVM, MS, Dipl. ACVIM, is LVMA Equine Committee professor and director of the Equine Health Studies Program at Louisiana State University's School of Veterinary Medicine. As an internal medicine specialist, Andrews research interests include equine gastric ulcer disease.

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