Equine Gastric Ulcer Syndrome (EGUS) is an all too common cause of poor performance in the equine athlete. There are several factors that lead to the development of gastric ulcers and while the current treatment modality is extremely effective, it takes a combination of management changes and interventions to prevent the development of future ulcers.
While everyone has an image in their head of what a horse with ulcers looks like – thin and anxious – studies have found a high prevalence of gastric ulcers in horses of all types of careers and lifestyles. Not surprisingly, top athletes like racehorses and endurance horses have an extremely high incidence of ulcers, up to 98%. However, in a group of Thoroughbred broodmares living on pasture with no clinical signs, 71% had ulcers. Another study looking at asymptomatic pleasure horses found ulcers in 53%. So even though your horse many not be an upper level athlete, anxious, stressed or showing clinical signs, gastric ulcers may still be present and affecting their performance.
In order to understand how ulcers form and how we can prevent them we must first know the anatomy of the horse’s stomach and the protective barriers that nature has provided. The lining of the equine stomach is divided into two sections, the squamous mucosa and the glandular mucosa. The squamous mucosa covers the upper portion of the stomach. This portion of the stomach does not produce any secretions that contribute to the digestion of feed. Because it does not secrete acids, it also does not produce a protective barrier for itself against these corrosive agents.
The lower portion of the stomach is covered by the glandular mucosa which contains the glands that produce the secretions that begin the breakdown of feed material. Because it is constantly bathed in an acidic solution, this portion of the stomach has a number of protective barriers to prevent the formation of gastric ulcers.
The two portions of the stomach are clearly divided by a pronounced raised line called the margo plicatus.
Acid contacting the squamous mucosa can occur when there is an increase in acid production and a shift in stomach fluids. The area of the squamous mucosa adjacent to the margo plicatus is the most common place for ulcers to develop.
Feed and Exercise to Prevent Ulcers
Studies have shown that management factors play an important role in the incidence of ulcers. Increased exercise and increased exercise intensity has been linked with ulcers because there is an increase in acid production as well as a decrease in stomach volume, making it easier for the acid to contact the unprotected squamous mucosa. The number of hours spent in a stall and on pasture is also directly related to ulcer formation. Horses are meant to be continuous grazers and the constant production of saliva leads to lower acid levels in the stomach. Studies have shown that more frequent feedings will decrease the incidence of ulcers: 75% of horses fed twice a day had ulcers whereas ulcers were present in only 57% of horses fed the same amount but over three feedings. In fact, one of the most reliable ways to induce gastric ulcers for the purpose of research studies is to remove all feed from horses for a set period of time.
Overdoing Anti-Inflammatories
Another way human intervention can lead to ulcers is through the use of non steroidal anti-inflammatory medications (NSAIDs), Bute and Banamine. This side effect most commonly occurs after an overdose or chronic use, however some horses can develop severe ulcers after a single appropriate dose. NSAIDs stop inflammation and pain by inhibiting prostaglandins. Blocking prostaglandins will decrease blood flow to the stomach lining and limit mucus production, taking away two protective functions of the stomach. Treatment with NSAIDs will also lead to increased production of HCl. Not every horse will develop ulcers on NSAIDs, but it is important to keep this in mind when administering these medications.
Symptoms of Gastric Ulcers
Gastric ulcers can present with numerous and varied symptoms, which makes them a differential in many types of cases and very difficult to diagnose just based on clinical signs. Horses can have a single episode or recurrent bouts of colic. Some horses will develop loose manure or a dull hair coat. Some of the most common complaints in horses with ulcers are poor appetite, weight loss and attitude changes, particularly around meal time when acid production is at its highest. Some horses grind their teeth or show behavioral changes, such as an unwillingness to work or even flank biting. Other times the effects are more subtle, causing a drop in performance for an elite athlete.
Diagnosing Equine Gastric Ulcers
The only definitive way to diagnose gastric ulcers in horses is to perform a gastroscopy and visually inspect the lining of the stomach. In order to perform this procedure the horse must be fasted for 8-12 hours to ensure their stomach is empty at the time of the exam. A 3-meter long video endoscope is passed up one nostril, down the esophagus and into the stomach. In some cases the first inches of the small intestine can also be evaluated. Gastric ulcers are graded on a scale of 1-3 with 3 being the most severe. In Grade 1 ulcers there are pinpoint lesions in the squamous mucosa just above the margo plicatus. The remainder of the squamous mucosa may appear thickened and yellowed, called hyperkeratosis, a callusing reaction in response to chronic exposure to acid. Grade 2 ulcers are larger and more extensive, occurring further up into the squamous mucosa and the hyperkeratosis can be more pronounced. Grade 3 ulcers are the most severe with complete obliteration of the normal demarcation of the margo plicatus and islands of hyperkeratotic squamous mucosa surrounded by ulcers that are actively bleeding.
Treatment for Gastric Ulcers
When ulcers have been diagnosed, or suspected in the absence of a gastroscopy, a treatment regime can be enforced. There is only one FDA-approved drug that has proven efficacy in the treatment and prevention of gastric ulcers: Gastrogard. Omeprazole , the active drug in Gastrogard is a proton pump inhibitor, blocking the stomach’s ability to produce acid. In a field study performed in 2001, horses with gastric ulcers, treated with a 28-day course of Gastrogard, showed improved performance, weight gain and an improvement in attitude, appetite and hair coat. Additionally, 94% had improvement or healing of their ulcers on repeat gastroscopy.
There are other products that contain the same active ingredient as Gastrogard, usually at a fraction of the price. However, these compounded drugs are formulated outside the scope of the FDA and therefore, there is no way to know if they contain the promised amount of active ingredient. Dr. Scott Stanley of the University of California, Davis compared several compounded omeprazole products to Gastrogard and showed that some formulations had only 63% of the label claim and after 60 days on the shelf that number dropped to less than 17%. In another research study out of UC Davis, Dr. Jack Snyder showed that a compounded omperazole failed to heal gastric ulcers when compared to Gastrogard. So while it may be tempting to save money, you will not see the same results.
Creating a healthy gastric environment involves increasing the amount of time on pasture and splitting grain into multiple small feedings throughout the day. While feeding every six hours may be ideal, it is not practical. Simply breaking the total day’s ration into three feedings can make a significant difference.
Providing horses with a constant source of roughage will help increase their saliva production and decrease their acid production. For horses that tend to eat their daily ration of hay in a flash, try using hay nets with smaller holes. There is also evidence that horses fed alfalfa may be less likely to develop ulcers due to its high calcium content. Decreasing the incidence or duration of stressful situations and altering the intensity of a horse’s exercise program may also help by decreasing some of the risk factors discussed earlier.
There are also hundreds of dietary supplements available that promise to treat or prevent ulcers. Very few have scientific studies to back these claims. Some popular supplements such as Neigh-lox, contain aluminum hydroxide that coats the stomach and neutralizes acid to prevent ulcer formation. Studies using seabuckthorn berry extract showed the product prevented ulcers but did not improve ulcer scores in horses already affected. Anecdotally, aloe vera-containing supplements improve the attitude and appetite of horses with suspected ulcers. A most recent study investigated SmartGut Ultra, which contains seabuckthorn berry in addition to glutamine, pectin, lecithin and aloe vera. Horses given this product developed less severe experimentally induced ulcers than horses on no gastroprotectant agents. Again these products will not treat existing ulcers and may not provide complete protection but they do appear to temper the formation of new ulcers.
