A Tale of Two Equine Gastric Ulcer Syndromes
Understand the distinctions between squamous and glandular disease, so you can help your horse avoid painful gastric ulcers
It’s been more than 20 years since the equine veterinary community adopted the term equine gastric ulcer syndrome (EGUS) to describe the painful lesions that can form in the upper squamous or lower glandular portions of the horse’s stomach. Since then, researchers have devoted significant time and resources to studying the syndrome, yet much remains unknown.
“The more evidence we get, the clearer it is that in most cases, (squamous and glandular disease) are two separate entities that just happen to occur in the same place,” says Ben Sykes, BSc, BVMS, MS, MBA, Dipl. ACVIM and ECEIM, PhD, FHEA, a veterinarian, gastrointestinal disease researcher, and associate professor in equine medicine at Massey University, in Palmerston North, New Zealand.
Sykes compares equine squamous gastric disease (ESGD) and equine glandular gastric disease (EGGD) to lameness. A horse can have a foot or fetlock lameness, both of which affect the leg and produce similar clinical signs, but the reasons for the lameness are distinct. Likewise, ESGD and EGGD both affect the stomach, but their causes differ markedly.
In this article we’ll break down information detailed in the 2015 European College of Equine Internal Medicine Consensus Statement for EGUS, which Sykes co-authored. While veterinarians worldwide still consider this publication the go-to document for “everything EGUS,” we now have more details regarding risk factors for and clinical signs, treatment, and prevention of ESGD and EGGD.
Equine squamous gastric disease describes ulcers occurring in the squamous region of the stomach—the upper third where the esophagus enters. The squamous region is lined with stratified epithelial (skin) cells and void of glands and a mucous lining, making it sensitive to the damaging effects of acidic gastric juice.
“I think of ESGD as 80% related to environment and management and 20% related to horse-specific factors,” Sykes says. In most cases the environment and management are what create the risk. “Breed plays less of a role in ESGD risk,” he says. “For example, although Thoroughbreds are overrepresented for ESGD, this is largely because of use rather than breed itself. But there is a subset of horses, the 20%, that are individually predisposed and, as such, very sensitive to the risk of disease. These horses can be particularly challenging to manage and require a very high level of attention to detail.”
Key risk factors for ESGD include:
Quantity and type of roughage
Horses should consume at least 1.5-2% of their body weight in roughage—hay and pasture—per day. For an average 1,000-pound horse, this is 20 pounds.
Horses should always have access to hay when stalled or in a drylot without grass, says Frank M. Andrews, DVM, MS, Dipl. ACVIM, LVMA Equine Committee professor and director of the Equine Health Studies Program at Louisiana State University’s School of Veterinary Medicine, in Baton Rouge.
Overweight horses or those with insulin dysregulation or equine metabolic syndrome present a unique challenge for managing ESGD because nutritionists typically recommend feeding at a rate of 1.25-1.5% body weight/day in forage for calorie control. This approach is contrary to EGUS feeding recommendations, increases the risk of negative behaviors, and can have welfare implications.
One solution to feeding horses on restricted diets is to offer forages of low to medium nutritional quality that provide less energy (calories) but the same amount of fiber as higher-quality hays.
Adding calories with concentrates
Horses performing at high levels often require more calories than can be derived from forage alone. While many owners’ solution is to add two concentrate meals to their horses’ daily diets, the 2015 consensus statement notes feeding concentrates can increase the likelihood of ESGD. Rather, says Sykes, the first thing to do after ensuring horses have adequate access to roughage is to add oil.
“Up to 1 milliliter/kilogram body weight/day can be slowly introduced to the diet, which is about 1 cup twice daily,” he says.
Alongside a low-calorie supplemental feed or a vitamin and mineral balancer, Sykes says this combination can meet many horses’ energy and nutritional needs without adding concentrates.
“I most commonly use corn, canola, or vegetable oil, as they are cheap and easy to access,” he says.
Some horses require more energy than even the oil provides. “Hard keepers and the upper echelon of performance horses, such as three-day eventers, racehorses, and endurance horses, often require concentrates,” Sykes says. “If so, these should ideally, depending on the amount, be fed three to four times a day, not just twice.”
Andrews adds, “I recommend that owners and trainers weigh the grain before feeding to make sure the horse is getting the amount that is recommended. I find that many owners and trainers say they are feeding 5 pounds but usually they are feeding 7-10 pounds because they just go by the scoop.”
For both gastric and hindgut (the GI tract beyond the small intestine) health, Sykes and Andrews encourage horse owners to seek low-carbohydrate feeds. Sykes says beet pulp, a low-cost, highly digestible form of fiber, is a useful addition to these diets and “has been shown to have protective effects against ESGD in its own right.”
Timing of roughage meals
Owners must also think about when their horses eat. Horses naturally graze intermittently 24/7 but typically choose to fast and rest for a short period each night.
“This is usually between midnight and 6 a.m.,” says Andrews. “The stomach pH decreases during this period as well, which could be because they are not eating, producing saliva, or there is a nocturnal increase in acid secretion as with people.”
“Saliva acts as a buffer, protecting the squamous part of the stomach against acid,” Sykes explains. “When the stomach lies empty for prolonged periods of time, acid can splash up from the glandular region—the lower two-thirds of the stomach where the gastric contents pool.”
This splash effect contributes to ESGD, Andrews says, and “is most serious when horses perform intense exercise with an empty stomach after an all-night fast.”
Feeding alfalfa, which is high in protein and calcium carbonate (“like TUMS for horses,” says Andrews), before exercise might help reduce ESGD risk. Alfalfa hay can “top off” the roughage ball floating in the gastric juices. This can help prevent the acid from splashing onto and damaging the squamous epithelium.
“The idea of pre-exercise feeding is to ensure we feed our hay, especially alfalfa, strategically to get the best bang for our buck, rather than an arbitrary twice-a-day approach,” Sykes says. “As long as horses have access to roughage throughout the day, exercising in the afternoon, rather than the morning, also reduces the risk of ESGD, as horses will typically have spent most of the day (consuming forage), thus reducing the acid load in their stomachs.”
Amount of exercise
How much a horse works, rather than intensity, is the major contributor to ESGD risk, says Sykes.
“For ESGD, intensity plays some role in disease risk, but it is the cumulative number of minutes in a week at a trot or above that needs to be primarily considered,” he says.
While horses must train to gain fitness and do their jobs, Sykes says we should focus on the quality, not quantity, of training. “Unnecessarily long warmup or cool-down periods should be avoided,” he says.
Those extra minutes spent warming up and cooling down excessively add to the total exercise time, therefore increasing the risk of ESGD. This is a newer concept in ESGD research, says Sykes.
In contrast to ESGD, where environment and management are major risk factors, EGGD risk factors appear to be primarily linked to the horse’s individual sensitivity; Sykes considers them 80% horse-specific and 20% environment and management.
“Equine glandular gastric disease is not a disease of roughage and carbohydrates,” says Sykes. “This is a really important distinction.
“So, although the above recommendations for optimizing roughage intake and reducing carbohydrates remain important for reducing ESGD and hindgut disease risk, they have no direct bearing on EGGD risk,” he adds, noting it will take more than diet modification to reduce that risk.
Sykes says the single biggest risk factor for EGGD is being a Warmblood, with behavioral stress an important exacerbator. In one study in which researchers assessed horses’ response to a novel stressor, those with an exaggerated response had higher rates of EGGD and exaggerated cortisol (stress hormone) responses.
“The more riders and handlers a horse has, the higher the risk of EGGD (Hewetson et al., 2016), which further supports the idea that behavioral stress is important in disease risk,” says Sykes.
Additionally, researchers have identified exercise as a risk factor for EGGD. Unlike ESGD, however, it is not the quantity of exercise but the frequency. In a 2019 study Sykes found horses exercising four or fewer days a week were at a lower risk of developing glandular ulcers than horses exercising five or more days.
“The absence of rest days significantly increases the risk of EGGD,” he says. “Ensuring adequate rest days is one of the easiest EGGD risk factors to reduce with management changes.”
Finally, isolation is an additional source of stress that might contribute to EGGD.
Managing EGUS and Reducing Risk
Before reaching for the ulcer meds, take nonmedical steps to try to rebuild a healthy gastric environment.
For ESGD horses Sykes recommends ensuring continuous access to roughage. Use slow feeders or slow-feed haynets, long-stem hay, and, in some cases, lower-quality forage.
After addressing the diet, look for ways to reduce the amount of time you exercise your horse.
“Increasing the number of rest days allows you to focus on your quality of engagement with your horse,” he says. “This is particularly important for horses with EGGD. Building in activities that decrease your horse’s stress … should also decrease risk. Consider massage, music therapy, grooming, or other activities that reduce the stress associated with handling and exercise.”
When the management approach is insufficient, it’s time to turn to medication.
“For ESGD, omeprazole is the mainstay of treatment,” says Andrews.
An important change to the 2015 consensus statement is an increased understanding of the negative impact food has on omeprazole absorption (TheHorse.com/197576).
Sykes, who investigated this topic during his doctoral studies, says, “My work showed that if we don’t give omeprazole on an empty stomach, we dramatically reduce its ability to suppress acid production and, thus, its ability to heal ulcers, especially glandular ulcers.”
In fact, in some horses Sykes found no meaningful acid suppression if they had had unlimited access to hay overnight, even when given the full treatment dose of omeprazole.
This means caretakers should fast these horses from approximately 11 p.m. and administer the omeprazole first thing in the morning, followed by feeding 30 to 60 minutes later.
Sykes acknowledges this recommendation is somewhat counterintuitive given how important continuous access to hay is for ESGD prevention.
“Because we get better absorption (fasted horses absorb two to three times as much drug as fed horses), we get much better acid suppression, offsetting the risk of fasting the horse overnight during the treatment period,” he explains. “Once we come off treatment, we go back to the cornerstone prevention recommendation of ensuring access to roughage at all times.”
While Andrews does not fast horses overnight, he does recommend waiting at least 60 minutes for the drug to be absorbed into the bloodstream and reach maximum blood concentration.
“Then feed the horse, starting with hay,” he says. “After about 30 minutes, feed the grain portion of the diet (if required). The hay will stretch the stomach, and the omeprazole will concentrate in the acid-producing cells of the stomach.”
Without management changes, however, squamous ulcers will recur, which is why various omeprazole concentrations and treatment regimens exist. Both Sykes and Andrews emphasize the importance of your veterinarian determining the best omeprazole dose for your horse.
For horses with EGGD, omeprazole and misoprostol are the mainstays of treatment. Some animals might need additional pharmaceutical agents such as sucralfate but, again, your veterinarian should recommend the best course of treatment.
“There is no universally accepted treatment that every horse with EGGD will respond to,” says Sykes. “It becomes a case-by-case decision.
“When it comes to prevention, we have no evidence to support the use of low-dose omeprazole for EGGD,” he adds. “In fact, the evidence we have suggests that it is unlikely that we achieve adequate acid suppression at low doses.”
Sykes says management plays a key role in preventing EGGD but, again, in a different way than ESGD prevention strategies. Focus on providing adequate rest days and reducing environmental stress.
(Read more about gastric ulcer therapies at TheHorse.com/166040.)
Our sources emphasize that although ESGD and EGGD live under the EGUS umbrella, they’re incredibly different conditions. Both require management modifications for prevention, but the recommendations are markedly distinct: Forage for ESGD and reduced stress for EGGD. One thing they have in common is medication isn’t a cure-all for either.
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