Treating horse ulcers requires a combination of medication, dietary changes, and management adjustments, with most cases improving within 28 days on the right protocol. The specific approach depends on where the ulcers are located in the stomach, because the two types of equine gastric ulcers respond differently to treatment.
Two Types of Ulcers, Two Approaches
Horses develop ulcers in two distinct regions of the stomach, and this matters for treatment. The upper portion is lined with squamous tissue (similar to the esophagus), while the lower portion has glandular tissue that produces mucus and acid. Squamous ulcers are far more common, especially in performance horses, and they respond well to standard acid-suppressing medication. Glandular ulcers are trickier. They often need longer treatment, sometimes different drugs, and don’t always heal on the same timeline.
A veterinarian confirms the diagnosis with gastroscopy, a procedure where a camera is passed into the stomach. Squamous ulcers are graded on a 0 to 4 scale, from intact tissue (grade 0) through small focal lesions (grade 2) up to extensive deep ulceration (grade 4). For glandular ulcers, there’s no reliable grading system yet. Instead, vets describe them by appearance (hemorrhagic, ulcerated, raised, depressed) and location. This distinction guides how aggressive the treatment plan needs to be.
Omeprazole: The Core Medication
The primary treatment for equine gastric ulcers is omeprazole, a proton pump inhibitor that suppresses stomach acid production. The FDA-approved equine formulation (GastroGard) is given orally once daily at 4 mg/kg body weight for 28 days. After that initial course, the dose drops to 2 mg/kg daily for at least another four weeks to prevent recurrence.
This protocol works well for squamous ulcers. In clinical trials, 77% of horses had complete healing by day 28, and 92% showed significant improvement. That means roughly 1 in 4 horses won’t fully heal on the first round, though most of those still improve substantially. Horses that don’t respond may need an extended course or a reassessment of contributing factors like diet and workload.
Glandular ulcers are a different story. While omeprazole is still part of the protocol, healing typically requires 45 to 60 days of treatment. One study comparing treatment approaches found that a prostaglandin-boosting medication (misoprostol, given twice daily) outperformed the combination of omeprazole plus sucralfate for glandular disease. If your horse has glandular ulcers that aren’t responding to omeprazole alone, your vet may adjust the protocol accordingly.
Why Diet Is Part of the Treatment
Medication alone won’t solve the problem if the horse’s diet keeps creating the conditions for ulcers. The single most impactful dietary change is incorporating alfalfa hay. Alfalfa has roughly double the calcium content of typical grass hay (14.4 mg/g vs. 7.4 mg/g dry weight) and significantly more protein (21% crude protein compared to about 8% in bromegrass hay). Both calcium and protein buffer stomach acid, raising the pH and protecting the vulnerable squamous lining. Research has shown this buffering effect lasts for about five hours after a meal.
UC Davis recommends keeping alfalfa below 50% of total roughage to avoid the risk of intestite stone formation (enteroliths), but even a moderate amount provides meaningful protection. Feeding a small portion of alfalfa 30 minutes before intense exercise is a particularly useful strategy, because it creates a buffer right when the horse needs it most.
Corn oil is another dietary addition worth considering. It increases prostaglandin production in the stomach lining, which stimulates mucus secretion, inhibits the breakdown of protective tissue, and raises gastric pH. The omega-6 fatty acids in corn oil, particularly linoleic acid, drive this effect. Your vet can advise on the appropriate amount for your horse’s size and workload.
Feeding Schedule Matters as Much as Feed Choice
Horses evolved to graze almost continuously. In the wild, they rarely go more than 3 to 4 hours without eating. A horse’s stomach produces acid around the clock, whether or not there’s food in it. When the stomach is empty, that acid sits in direct contact with the unprotected squamous lining, exactly the tissue most prone to ulceration.
If your horse doesn’t have access to pasture or free-choice hay, feed at least twice daily to minimize the gap between meals. Three or four smaller meals are better than two large ones. Slow feeders, hay nets, or track systems that spread forage across the day can help approximate the natural grazing pattern. The goal is simple: reduce the amount of time the stomach sits empty.
Exercise, Stress, and the Acid Splash Effect
During exercise, increased abdominal pressure causes acidic stomach fluid to splash upward, exposing the squamous lining to acid it wouldn’t normally contact. This is one reason ulcers are so prevalent in racehorses and sport horses. The more intense the work, the greater the splash effect.
For horses being treated for ulcers, reducing training intensity is an important part of recovery. Turnout on pasture, where the horse can move freely and graze, is ideal during the treatment period. Feeding that small alfalfa meal before exercise helps by putting a fibrous mat in the stomach that absorbs some of the acid and reduces splashing.
Stress beyond exercise also plays a role. Frequent trailering, stall confinement, changes in routine, and social isolation all increase ulcer risk. During treatment, limiting these stressors wherever possible gives the stomach lining its best chance to heal. Once ulcers have resolved, be aware that returning to intense training without preventive measures makes recurrence likely.
Preventing Ulcers From Coming Back
Recurrence is the biggest challenge with equine gastric ulcers. Horses that have had ulcers are prone to developing them again, especially if the underlying management factors don’t change. A prevention plan includes several layers:
- Continued low-dose omeprazole at 2 mg/kg for at least four weeks after the treatment course ends, tapering under veterinary guidance rather than stopping abruptly.
- Consistent forage access with no fasting gaps longer than 3 to 4 hours. Prioritize hay or pasture over concentrate-heavy diets.
- Alfalfa in the ration for its buffering effect, particularly before exercise sessions.
- Corn oil supplementation to support the stomach’s natural mucus defenses.
- Gradual return to work with attention to how the horse responds. Behavioral signs like girthiness, poor appetite, or resistance under saddle can signal a flare-up before it becomes severe.
Follow-up gastroscopy is the only way to confirm ulcers have fully healed. Behavioral improvement alone isn’t always reliable, since horses can seem better while lesions are still present. Many vets recommend a scope at the end of the treatment course, and again if symptoms return after medication stops. Catching early-stage lesions before they progress to grade 3 or 4 makes retreatment faster and less costly.