How to Treat and Prevent Ulcers in Horses: Symptoms, Causes, Diet & EGUS Guide

How to Treat and Prevent Ulcers in Horses: Symptoms, Causes, Diet & EGUS Guide

Manan Chawla

Ulcers in horses are one of the most common digestive disorders horses face, with prevalence estimated at between 50 and 90% depending on the type and level of work the horse is in. They occur when stomach acid wears away the stomach lining, producing lesions that can affect a horse's appetite, behavior, performance, and general physical condition. The good news is that with the right diagnosis, the correct medication, and targeted feeding and management changes, most horses recover fully within four to eight weeks.

Key Takeways

  • EGUS is the umbrella term for horse stomach ulcers, covering two distinct types: ESGD (squamous) and EGGD (glandular), each requiring different treatment

  • The most common risk factors are infrequent feeding, high-grain diets, intense exercise, NSAID use, and stress.

  • Symptoms range from subtle signs like poor appetite, girthiness, and dull coat to severe colic and teeth grinding, and symptom severity does not always reflect ulcer severity.

  • Gastroscopy is the only way to definitively diagnose EGUS and identify which type is present.

  • Omeprazole is the first-line treatment for squamous ulcers; misoprostol is more effective for glandular ulcers.

  • A forage-based, low-starch diet is essential for both recovery and long-term prevention.

  • Most horses recover fully within four to eight weeks with the right treatment and management plan.

What Is Equine Gastric Ulcer Syndrome and its Types?

Equine Gastric Ulcer Syndrome, also known as EGUS, covers all gastric ulcer conditions in horses. It affects an estimated 60% of show horses and up to 90% of those in high-performance work such as racing, endurance, and showing. There are two distinct types, ESGD and EGGD, that affect different regions of the stomach, have different causes, and need different treatments.

Horses produce stomach acid continuously, 24 hours a day, whether they are eating or not. In the wild, horses graze almost constantly, which means forage and saliva work together to keep stomach acid in check throughout the day. Modern management practices, with extended gaps between meals and diets heavy in grain, often remove that natural protection entirely.

The horse's stomach is divided into two regions:

  • Squamous region (upper): This area has no built-in defense against acid and depends on a steady supply of forage and saliva to stay protected. This is where most ulcers form, classified as ESGD (Equine Squamous Gastric Disease).
  • Glandular region (lower): Produces acid but is lined with a mucus and bicarbonate barrier. When that barrier breaks down, ulcers develop here, classified as EGGD (Equine Glandular Gastric Disease).

Understanding ESGD vs EGGD is the starting point for any effective treatment plan. A horse treated for the wrong ulcer type is unlikely to recover fully, which is why gastroscopy is always the essential first step.

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Causes of Ulcers in Horses

Horses get ulcers when acid production overwhelms the stomach's natural defenses. Understanding why horses get ulcers comes down to a core set of risk factors for gastric ulcers in horses: infrequent feeding, high-grain diets, intense exercise, NSAID use, and stress. In most cases, several of these are happening at once.

  • Exercise compresses the stomach and forces acid upward onto the unprotected squamous lining. The harder and more frequently a horse works, the greater the exposure, which is why squamous ulcers are so prevalent in performance horses.
  • Long gaps between meals leave the stomach producing acid with nothing to neutralize it. Horses going more than six hours without forage have a fourfold higher ulcer risk.
  • High-grain diets cause bacteria to ferment excess carbohydrates in the stomach, producing lactic acid and volatile fatty acids that directly erode the squamous lining.
  • NSAID use (phenylbutazone/bute, Banamine, ketoprofen) weakens the glandular protective barrier by reducing mucus, bicarbonate, and prostaglandin production. It is one of the clearest known contributors to EGGD.
  • Stress raises cortisol levels, which suppresses the stomach lining's protective mechanisms. Transport, stall confinement, intense training, and social disruption within the herd all increase risk.
  • Lack of water access is easy to overlook, but horses without constant fresh water are 2.5 times more likely to develop ulcers.

Signs of Ulcers in Horses

The most common signs of ulcers in horses are poor appetite, weight loss, dull coat, low-grade colic, girthiness, and changes in behavior or ridden performance. Symptom severity does not always reflect how serious the ulceration is — some horses with Grade 4 lesions show very little outwardly, while others with mild ulcers can be difficult, sore, and losing condition.

Subtle signs: poor appetite, dullness, unexplained weight loss, a poor coat, recurring low-grade colic, and sensitivity when being girthed or tacked up. These are the signs most often misattributed to saddle fit issues or a horse simply having a difficult week.

Behavioral and performance signs: resistance under saddle, bucking, napping, biting, increased spookiness, or walking away from food mid-meal as eating causes discomfort.

Severe signs: acute abdominal pain, grinding of teeth (bruxism), and lying on the back, which can relieve pressure from severe gastric ulceration.

In foals, signs include intermittent colic after feeding, reduced nursing, diarrhea, a pot-bellied appearance, and excess salivation. These typically indicate severe ulceration and need immediate veterinary attention.

Diagnosing and Treating Horse Ulcers

How Are Horse Ulcers Diagnosed?

Gastric ulcers in horses can only be definitively diagnosed through gastroscopy. No combination of clinical signs, however convincing, is enough to confirm the diagnosis or identify the ulcer type.

Gastroscopy involves passing a flexible camera through the nostrils into the stomach under standing sedation, after a 12 to 16-hour fast. Ulcers are graded on a 0 to 4 scale, with Grade 4 representing the most severe, widespread lesions. The procedure also identifies whether ulcers are squamous, glandular, or both, which is the foundation of an effective treatment plan.

Horse Ulcer Treatment: Matching Medication to Ulcer Type

Knowing how to treat ulcers in horses starts with knowing which type you are dealing with. Omeprazole is the standard for squamous ulcers (ESGD), while misoprostol is more effective for glandular ulcers (EGGD). Using the wrong medication is one of the most common reasons horses fail to recover fully.

Omeprazole is the only FDA-approved treatment for equine gastric ulcers and the first-line choice for ESGD. It reduces acid production and allows the squamous mucosa to heal. The standard dose is 4 mg/kg/day for 28 days, with 86% of squamous ulcers healed within this period, given one hour before feeding. A lower preventive dose is available for stressful events. Compounded omeprazole products consistently show less active drug than labeled, and FDA-approved formulations are strongly recommended.

Misoprostol is the preferred treatment for EGGD. Unlike omeprazole, it stimulates mucus and bicarbonate production to rebuild the glandular barrier. A clinical trial found misoprostol to be superior to omeprazole specifically for glandular ulcers.

Sucralfate is sometimes used alongside omeprazole in severe cases. It forms a physical coating over ulcerated tissue, increases blood flow, and helps manage pain. It must not be given at the same time of day as omeprazole, as this impairs absorption of both.

A follow-up gastroscopy after treatment confirms whether healing is complete before returning to hard work.

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Diet for Horses with Gastric Ulcers

The best diet for a horse with ulcers is built around continuous forage access, minimal grain, and oil-based calories where extra energy is needed. A forage diet for horses with ulcers is the foundation of horse gut health and recovery — without it, even the best medication is working against the horse every day.

Forage first: Horses are built to graze for up to 16 hours a day. When forage is available consistently, saliva production stays steady, and the stomach maintains a natural buffer against acid throughout the day. Use slow-feed hay nets for stabled horses to extend eating time and close the gaps between meals. Never allow more than six hours without forage.

Alfalfa for horse ulcers: Alfalfa has a higher calcium content than grass hay, giving it natural acid-buffering properties. Feeding a small portion 30 minutes before exercise helps protect the squamous mucosa during work. Keep it below 50% of total roughage to reduce the risk of enterolith formation.

Low starch horse diet: Cutting grain removes the fermentable carbohydrate load that produces damaging acids in the stomach. Where extra calories are needed, replace concentrates with linseed (flax) oil. If grain cannot be eliminated, feed it in small, frequent portions and choose low-starch formulated feeds.

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What to feed a horse with Ulcers: Quick Reference

Recommended Avoid or Reduce
Continuous pasture or slow-feed hay nets Gaps of more than 6 hours without forage
Alfalfa before exercise (under 50% of roughage) Large grain or concentrate meals
Linseed or flax oil for extra calories High-starch feeds like oats and corn
Small, frequent meals if grain is needed Exercising on a completely empty stomach
Fresh water available at all times Abrupt changes to the diet

Horse Ulcer Prevention: What Actually Works

The most effective prevention strategies are maximizing turnout, maintaining consistent feeding routines, always feeding before exercise, and reducing stressors in the stable environment. Horses that have had ulcers before may benefit from a preventive omeprazole course during periods of high stress, and it is worth discussing this option with your vet ahead of time.

Maximize turnout: Regular time at pasture lowers stress levels, encourages natural grazing behavior, and keeps the stomach receiving a steady supply of forage. Even getting a horse out for part of the day has a measurable impact.

Keep routines stable: Consistent feeding schedules, predictable work patterns, and a settled herd environment all help reduce the background stress that contributes to glandular ulceration. Shifts in herd dynamics can unsettle horses more than many owners anticipate.

Feed before exercise: Offering a small amount of hay or alfalfa 30 to 60 minutes before ridden work helps buffer stomach acid and reduces the physical compression that occurs during exercise.

Manage the stable environment: Keep hay available at all times, ensure horses can see their neighbors, and use enrichment activities to reduce boredom. Mirrors may also help ease isolation stress in some horses. Purpose-designed equine music has been shown in several studies to lower stress indicators in stabled horses, making it a worthwhile addition to a stable routine.

Plan ahead for stressful events: For horses with a history of ulcers, discuss a preventive low-dose omeprazole protocol with your vet before known stressors such as competition, transport, or significant changes in environment or routine. A year-round gastric health plan is the most reliable way to keep ulcers from recurring.

Most Horse Ulcers Are Fully Recoverable

EGUS is widespread, but it is far from a permanent sentence for your horse. With the right medication, dietary adjustments, and management changes in place, most horses make a full recovery within four to eight weeks. Those that do best tend to have owners who pursued the correct diagnosis early, matched the treatment to the ulcer type, shifted to a forage-based low starch diet, and made lasting changes to the daily routine rather than just treating the immediate symptoms.

If any of this sounds familiar, the best starting point is a conversation with your vet. Gastroscopy takes the uncertainty out of the diagnosis, and once you have a clear picture of what you are dealing with, putting a recovery plan together is generally less daunting than most owners anticipate.

References

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