Your Horse's Health
Veterinary Medicine with
Wade Tenney, DVM

Published in Bay Area Equestrian Network June 2009.
"EGUS": Equine Gastric Ulcer Syndrome
How many of you can think back to vague signs in your horse including intermittent colic, poor performance, changes in attitude, poor hair coat or poor
body condition? It may be worth looking into EGUS or Equine Gastric Ulcer
Syndrome in your horse. EGUS refers to the vast array of clinical signs
associated with erosions or ulceration of the horse's stomach and duodenum (the
first part of the small intestines). The incidence of ulcers is higher than most
people think. Studies have found ulcers in as many as 94% of race horses, 58%
of performance horses and 57% of foals.
Anatomy & Physiology
The horse's stomach basically has 2 regions separated by a distinct junction known as the margo plicatus. The lower portion of the stomach, known
as the "glandular region" is responsible for the secretion of hydrochloric acid,
pepsin and other enzymes that aid in digestion. The top portion closest to the
mouth is made of squamous cells, similar to those seen in the esophagus. This
squamous portion has limited protection against the digestive properties of the
acidic enzymes produced in the stomach. Under certain conditions, the
squamous portion of the stomach has increased exposure to the acidic
environment and the enzymes begin to erode into the mucosal lining of the
Predisposing factors
Any time the squamous portion of the stomach has increased acid exposure, there is a risk for ulceration. The horse is designed to be a continualgrazer, which is helpful in several ways. When a horse is allowed to eat smallamounts throughout the day, the constant presence of feed material helpsprotect the stomach lining. Unfortunately many horses are fed just twice daily,leaving the stomach empty and exposed to acid in between feedings. Also, grassand hay are good buffers, lowering the acidic content of the stomach. Grains, onthe other hand, increase the acidity of the horse's stomach.
Stressful conditions have also been associated with the formation of gastric ulcers. This can include new environments, stall confinement for lay-up/rehab, competition and even transportation. In one study, horses weretrailered for 4 hours to a new site, placed in stalls, fed twice daily and exercisedtwice daily for 3 days. Then they were trailered 4 hours back to the original site.
This scenario is a common one for many horses today, yet it induced ulcerationin 7 of the 10 horses.
The administration of non-steroidal anti-inflammatories such as Bute or Banamine has also been linked to the development of ulcerations. NSAIDScause a decrease in Prostaglandin E, which is responsible for the protection of the glandular mucosa (stomach lining). For this reason, we try to limit NSAIDadministration to 2 grams or less daily and for less than 7-10 days in a row ifpossible.
There may also be a correlation between exercise and ulcers, explaining the high incidence in the performance horse. Preliminary studies have showedan increase in intra-abdominal pressure with exercise. This leads to compressionof the stomach, raising the acidic contents up into the unprotected squamousregion.
Clinical signs such as chronic colic, poor performance, weight loss, changes in attitudeand poor hair coat may raise one's index ofsuspicion for gastric ulceration. However, theonly definitive way to diagnose ulcers is toactually visualize the stomach via gastroscopy.
However, the horse needs to be held off feedfor 12-18 hours prior to the exam so that feedmaterial does not obstruct our view. Agastroscope is passed through the horse'snose, down the esophagus and into thestomach where we can visualize the stomachlining. If ulcers are noted, they can be scoredfrom 0-4 depending on the severity ofreddening, thickening, and erosions orulceration.
There are several options for the treatment of gastric ulcers, all aimed in decreasing or neutralizing the stomach acids. Treatment may be dictated by thelocation, severity or duration of the lesion or by financial constraints. Protonpump inhibitors work by stopping the secretion of hydrogen ions from the cells inthe stomach. Gastrogard (Omeprazole) is the most commonly used proton pumpinhibitor and has been shown to decrease acid output within 5-8 hours ofreceiving the first dose. Gastrogard is a paste formulation that is generallyadministered daily for 28 days for the successful treatment of ulcers. H 2antagonists can also be used to treat ulcers by blocking certain receptors andcausing a decrease in hydrochloric acid secretion. H 2 antagonists such asCimetidine or Ranitdine are successful in treating ulcers, but typically have to begiven every 6-8 hours, which makes dosing more difficult. Sucralfate has beenused successfully in humans to treat and prevent stress-induced ulcers. It hasalso been used successfully in horses and works by coating the ulceratedmucosal lining and increasing mucous production. Unfortunately, Sucralfate mustalso be administered every 6-8 hours to be effective. Antacids have been used in horses, but have fallen out of favor due the very high dosages and frequentadministration that are required to be effective.
Many of today's horses are in heavy training or competition, travel extensively, stalled for much of the day and fed twice daily. All of theseconditions likely play a role in the high prevalence of ulcers today. However,there are steps that you can take to reduce the chance of your horse developingulcers. If your horse is fed primarily an all-concentrate diet (grains), try addingsome grass or hay to function as a buffer. Try to minimize the stress of longtrailer rides by breaking up the trip. Allow access to pasture when possible andintroduce a noon feeding to minimize the length of time the stomach is empty.
Also, consider Ulcergard during times of stress. Ulcergard is a less concentratedform of Gastrogard which is used to prevent (but not treat) ulcers. Giving yourhorse a daily dose of Ulcergard before and during competitions may give thatadded protection to prevent the formation of ulcers.
In many cases, these simple management changes may be enough to prevent gastric ulcers in your horse. If not, knowing what the signs are andinitiating early treatment are your best defense.
Wade Tenney, DVM* 1991 Cornell - BS in Animal Science.
* Four years on the Varsity Polo Team at Cornell* 1997 - Colorado State University, Doctorate of Veterinary Medicine* New Bolton Fellowship in Equine Reproduction - two years.
* Littleton Large Animal Clinic, Colorado - Associate for two years after a one- year internship* 2000-2005 - B.W. Furlong and Associates, Equine Veterinarians, P.A., Oldwick, New Jersey Special Focus: (in addition to general ambulatory practice): a. Equine Reproduction b. Nuclear Scintigraphy* 2005(R)2006 UC Davis Large Animal Ultrasound Internship* 2006(R)Joined SCEC


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