Preventing ulcers in horses comes down to mimicking how their digestive system evolved to work: near-constant access to forage, limited starch, and minimal prolonged fasting. Gastric ulcers affect an estimated 60 to 90 percent of performance horses, but the majority of cases are driven by management choices that can be changed. Understanding why ulcers form makes prevention straightforward.
Why Horses Are Prone to Ulcers
Unlike humans, who produce stomach acid mainly when eating, horses secrete hydrochloric acid continuously. This made sense when they spent 16 to 18 hours a day grazing, but it becomes a problem under modern management. The horse’s stomach has two distinct regions, and each develops ulcers for different reasons.
The upper portion (squamous mucosa) has no protective lining of its own. It relies entirely on saliva and a floating mat of forage to shield it from acid. The pH in the lower stomach sits around 2.9 at all times, while the upper region averages around 6.8 when the horse is eating normally. When the upper region loses that buffer, acid eats into the tissue and ulceration begins. Byproducts of bacterial fermentation of starch and sugar make the damage worse.
The lower portion (glandular mucosa) has built-in defenses, including a mucus barrier and blood flow that repairs minor damage. Ulcers here are less about excess acid and more about a breakdown of those protective mechanisms. NSAIDs, stress, and inflammation can all compromise the glandular lining. The exact mechanism is still not fully understood, but the practical takeaway is that upper and lower ulcers have different triggers and require different prevention strategies.
Keep Forage Available Throughout the Day
This is the single most effective thing you can do. When a horse chews forage, it produces large volumes of saliva containing bicarbonate, which neutralizes stomach acid. The longer a horse chews, the more saliva and bicarbonate it generates. Forage also forms a fibrous mat in the stomach that physically prevents acid from splashing up onto the unprotected upper lining.
Daytime fasting is particularly harmful. Research on intragastric pH shows that even short episodes of feed deprivation during the day and evening significantly drop the pH in the upper stomach compared to horses with continuous access to hay. A nocturnal pH decrease happens naturally even in horses that are fed, so the daytime hours are the critical window to manage. If your horse finishes its hay well before the next feeding, it’s spending hours with an empty, acid-filled stomach.
Practical solutions include using slow-feed hay nets, offering smaller hay portions more frequently, or turning out on pasture for longer periods. The goal is to eliminate gaps of more than a few hours without forage. Horses that eat meals of hay twice a day with nothing in between are at significantly higher risk.
Limit Starch and Sugar Per Meal
Large grain meals are one of the strongest dietary risk factors for squamous ulcers. Starch and sugar ferment in the stomach, producing volatile fatty acids that damage the upper lining, especially when pH is already low. The more grain per meal, the more fermentation and the longer the stomach stays acidic.
Penn State Extension recommends keeping sugar and starch below 1 gram per kilogram of body weight per meal, and below 2 grams per kilogram per day. For a 1,000-pound horse (roughly 450 kg), that means no more than 450 grams of sugar and starch in a single feeding and no more than 900 grams across the entire day. You can check the sugar and starch content on your feed tag and do the math for your horse’s weight. If your horse needs more calories than forage alone provides, split concentrate meals into three or more smaller feedings rather than two large ones.
Use Alfalfa as a Strategic Buffer
Alfalfa hay has a measurably higher buffering capacity than grass hay, thanks to its high calcium and protein content. Both calcium and protein help neutralize stomach acid on contact. Feeding a flake of alfalfa before exercise or as part of the regular hay ration can raise gastric pH and provide additional protection to the squamous lining.
You don’t need to switch entirely to alfalfa. Even a partial substitution, such as replacing one or two flakes of grass hay per day, provides meaningful buffering. For horses that can’t tolerate the higher calorie or protein content of alfalfa (easy keepers, horses with metabolic concerns), even a small amount fed 30 minutes before work can help.
Feed Before Exercise, Not After
During intense exercise, increased abdominal pressure compresses the stomach and pushes its highly acidic contents upward toward the unprotected squamous lining. This “splash effect” is one reason performance horses have such high ulcer rates. An empty stomach during work means there’s nothing but acid to splash around.
Feeding a small amount of forage, ideally including some alfalfa, about 30 minutes before riding gives the stomach a protective fiber mat and raises pH before compression begins. This doesn’t need to be a full meal. A couple of pounds of hay is enough to provide a buffer without making the horse uncomfortable during work.
Manage NSAID Use Carefully
Anti-inflammatory drugs like phenylbutazone (bute) are strongly linked to glandular ulcers in horses. In one study, all horses treated with phenylbutazone developed moderate to severe glandular ulceration, while untreated horses did not. The exact mechanism is still being investigated. Researchers initially suspected it was due to reduced prostaglandin levels compromising blood flow to the stomach lining, but prostaglandin levels actually increased during treatment, suggesting the pathway is more complex.
The practical implication is simple: use NSAIDs at the lowest effective dose for the shortest possible duration. If your horse needs prolonged anti-inflammatory therapy, talk to your veterinarian about alternatives or concurrent stomach protection. Routine use of bute for minor stiffness or as a preventive before competition adds up over time.
Consider Protective Supplements
Pectin-lecithin supplements work by forming a hydrophobic (water-repelling) barrier on the stomach’s mucosal surface, shielding it from acid contact. The horse’s upper stomach naturally has a layer of surface-active phospholipids that serve a similar protective function, and pectin-lecithin complexes reinforce that defense. These supplements are available as daily feed additives and are most useful for horses in ongoing work or those with a history of ulcers.
Other commonly used supplements include calcium and magnesium-based antacids, which provide short-term pH buffering, and seabuckthorn berry products. Supplements are best viewed as an added layer of protection on top of good management, not a substitute for fixing the feeding schedule or reducing starch intake.
Preventing Ulcer Recurrence
Horses that have already had ulcers are prone to recurrence, especially if the management factors that caused them haven’t changed. After treatment, the labeled protocol for omeprazole (the standard prescription treatment) recommends continuing at a lower maintenance dose for at least four additional weeks to prevent relapse. But medication alone won’t keep ulcers away if the horse goes back to long fasting periods, large grain meals, and heavy NSAID use.
The most durable prevention plan combines dietary changes (continuous forage access, limited starch, strategic alfalfa) with management adjustments (feeding before exercise, minimizing unnecessary NSAIDs, reducing stall confinement). Horses with access to pasture turnout consistently have lower ulcer rates than stall-kept horses, likely because they graze more continuously and experience less stress. Even a few extra hours of turnout per day can make a meaningful difference.