Equine ulcers were first recognized in horses more than 30 years ago.  Unbuffered acid, or acid exposure of non-glandular regions of the stomach not normally protected by mucus, can lead to erosion and ulcerations of the lining.

Now we know that gastric (stomach) ulcers affect many horses in stressful performance careers, even though some horses do not show obvious signs . Some of the early studies also looked at ulcers in foals.  Reports in the Equine Veterinary Journal in 1989 and 1996 by Dr Michael Murray stated that gastric ulcers affect up to 93% of racehorses, 60% of horses in other performance careers, and up to 59% of foals.

Further studies showed incidence of ulcers in show horses and pleasure horses was higher than horse owners suspected.  Subtle symptoms may go unnoticed, or be mistaken for other problems.  The best way to diagnose this condition is to look inside the stomach with an endoscope.

Signs of ulcers in foals are thought to include intermittent colic or diarrhea, rough hair coat, poor growth, or drooling.  Discomfort may be shown by grinding the teeth, lying on the back to try to ease abdominal pain, or interrupted nursing . The foal may nurse vigorously and then halt abruptly, due to pain in the stomach.

Dr Burt Staniar is currently involved with studies looking at ulcers in horses.  “Most of our work is focused on adult horses fed different types of diets;” he said.  “I am also familiar with the research done with young horses in training.  We don’t have a lot of data on ulceration in very young foals, however.  The problem of ulcers in young foals can be different, with different causes, and occurring in different places in the GI tract.”

Dr Carol Clark says neonatal foals (in the first two weeks of life) are much less at risk for ulcers, especially the classical gastroduodenal ulcer disease, than older foals.

“During the 1980s and 1990s, everyone was thinking that these young foals needed ulcer prevention, using Zantac and other acid-inhibiting medications,” she said.  “Since then there have been studies looking at foals that died, finding that only rarely do foals truly have gastroduodenal ulcer disease in the first weeks of life.  If a foal does rupture an ulcer (which is rare), it seems to be an ischemic event – like a blood clot or poor perfusion to the lining.  This is not something that ulcer medication can prevent.”

Many of the very young foals that are sick are already being treated with multiple drugs, and this is one less thing we need to give them.

“But as those foals get older, or if they have a painful condition early in life that requires pain relief via non-steroidal drugs (for an infected joint, for example), those are the foals I would consider putting on ulcer prevention medication.

If they get sick any time between two weeks of age and a year of age, ulcer prophylaxis is important.  A sick foal in the one to five month-old period of life could benefit from ulcer prevention.

“We see gastroduodenal ulcer disease in foals, and it’s different than the older-horse version of ulcers,” Clark said.  “Often in young foals it is glandular versus non-glandular, which is the typical type of ulcer disease we see in adult horses.  In foals it may involve the stomach, but in many cases it includes the first part of the small intestine, the duodenum.  This can result in strictures and be very serious.

“Affected foals can suddenly rupture and nobody even knew they were sick – though strictured foals don’t usually rupture.  More often they get a chronic form of ulcers with delayed gastric emptying, oesophageal reflux, and sometimes secondary liver dysfunction.  There are also a few affected foals that just blow out an ulcer in their stomach, with no warning.

“These cases may occur sporadically or sometimes in outbreaks on a farm,” Clark continued.  “We don’t see this as much as we used to.  Sometimes it is associated with rotavirus.  It sometimes comes in waves, and we’ve looked for infectious causes, but we can’t necessarily say that we know what those causes are.”

Healthy foals don’t seem to have many problems with ulcers, but there hasn’t been a lot of work done to confirm this.

Clark said in order to know for sure that an animal has ulcers, you have to check the stomach with an endoscope.  “I don’t know of any work that has been done looking at the occurrence of ulcers in foals that are not at a hospital.  Ulcers just don’t seem to be a very big problem in normal, healthy foals.

“We can do a lot more ulcer prevention in sales prep youngsters and horses in training than we can do for very young foals.  If you have a sick foal that is more than two weeks of age, you probably should have it on ulcer prevention, but beyond that there is not a lot we can do. If they are sick, we can try to keep them from getting ulcers during that time. We can’t really do much in the way of diet manipulations.

“Until they are weaned, they are on a milk diet, which is great, but once they go into the real world and start learning their job, then their normal management is changed a lot.  That’s when ulcers tend to happen in young adults, and it’s our goal to try to improve that situation.”

Yearlings and Young Horses in Training
“The biggest difference between foals less than six months of age and the older horses is that young adult horses don’t generally get the glandular disease we see in young foals,” Clark said.  “As we look at yearling age and going into training, these youngsters are much more at risk for non-glandular disease.”

The biggest risks are for young horses transitioning into training, often ones that are transported from the farm to a training facility.

“This is another big change in their life – not only a diet transition but also a lifestyle and environment transition.  We believe stress causes ulcers, and stress is certainly a part of what impacts the body’s ability to maintain homeostasis, so it probably increases the risk of ulcers, but stress by itself may not cause ulcers. It’s just one factor.

“Many of these youngsters are also being treated with NSAIDs (nonsteroidal anti-inflammatory drugs) for various reasons.  This puts them at risk for glandular disease, not only in the stomach but also in the hindgut.  We see a lot of youngsters – especially those being prepped for thoroughbred sales – that get too many NSAIDs and possibly even steroids.

“I see almost as much indication of hindgut problems in these young horses as gastric ulcers.  Colonic ulcers are harder to see, but what we do see is low protein levels because of loss from the gut.  Due to ulcerative colitis, often in the right dorsal colon, these horses are low on protein. It may not be profound – not be enough to need plasma – but it’s an indication that the horse is not handling the NSAIDs very well.”

This can vary a lot with the individual horse.

“Some horses can be given NSAIDs long-term and not show any drop in protein while other individuals are very sensitive to these drugs-and the hindgut is just as sensitive as the stomach,” Clark continued.  “Sometimes those horses have intermittent diarrhea – which is rarely a symptom of gastric ulcer disease but can be a symptom of hindgut ulcer disease.

“Diarrhea is not a symptom of gastric ulcers in adult horses but can be a symptom of gastric ulcer disease in a young foal.  Anything that causes abnormalities in the small intestine can cause intermittent diarrhea in the foal.”

Young horses getting ready for sales or being pushed in training should probably be maintained on some sort of ulcer prevention.  There are also other things that can reduce risk for ulcers, such as limiting NSAID use and conscientious  feeding strategies.

“A big component of the nutritional side of ulcers is the fact that the anatomy and physiology of the horse’s stomach is well adapted to a high forage diet.  Horses have been eating forage for millions of years.  One of the things the high forage diet offers is physically effective fibre.  This is not the same as chemical fibre, like you’ll find listed on a feed tag (like crude fibre content).  Physically effective fibre is actual fibre that causes the horse to chew.

“This kind of fibre also impacts the way feed behaves inside the stomach and moves through the rest of the tract.  When a horse is eating forage and long-stem fibre, this works well to prevent ulcers.

“Horses chew a lot when eating forage, and produce a lot of saliva-and saliva is a buffering agent in the stomach to neutralize acid.  The chewed-up fibre also helps the stomach; it creates layers of different particle sizes and probably helps to buffer the pH, particularly along the margo plicatus.  This is the line in the stomach that divides the two very distinct areas, separating the glandular portion from the non-glandular.

“Most ulcers in horses occur along that line and above it.  The stomach lining above that line is a stratified squamous epithelium with a layered-cell protection, kind of like our oesophagus.  Below that line, the stomach is protected by a mucous coating, produced by a very different type of (glandular) lining.

“This coating helps protect the stomach from the acid being secreted (that aids in digestion).  In a horse that is eating enough forage, that line sits above or right at the mat of forage that tends to float on top of the stomach contents.  Below that mat are the smaller particles such as grain, and fluid and a lot of the acids that break things down.

“In a horse transitioning into training, this situation may change.  This young horse has usually been moved off the farm where it grew up, out of the paddock, and is now at the training barn where it is fed only a few flakes of hay and getting a lot more grain.  Now the stomach may go empty for periods of time and may also have less of the long fibre in it.

“In addition, we know that when the horse runs, the stomach is affected.  Its stomach sits just underneath the diaphragm, so it tends to get squeezed during exertion.  If there isn’t enough substance in the stomach to prevent this squeezing, it pushes a lot of the material that was lower in the stomach (including the acid) into the upper regions of the stomach where it is not protected.

“If there was a way to make sure horses had a little more fibre in their stomachs when they are running, this could make a big difference.  I realize we can’t feed a lot of hay just before exercise because that would negatively impact the horse’s performance.  But having some fibre in there, meaning the horse has chewed and produced saliva, would be very helpful.  We have ways to keep hay in front of horses all the time and limit intake, so they can have access to fibre through the day. The hay nets with smaller holes work nicely, allowing horses to nibble continually, yet they can’t eat a lot at once. This means they are chewing and producing saliva.

“The only way that a horse produces saliva is by chewing.  If you can make horses chew more by giving them a little more fibre, it would help.  We know we shouldn’t feed horses a big meal (hay or grain) just before they run, but if they had a limit-feed hay net, they could at least get a little fibre in the morning before they run, and we might be able to reduce the risk of ulcers.

“The stomach wouldn’t be quite as empty, and they would also have enough saliva to help buffer the acid that was present in the stomach.  Ultimately the pH would be lower, and if the stomach contents did splash into that upper region, it might not be quite as damaging.

“Horses need something in their stomach. If they do have to go without feed, we should limit those times to less than four-hour periods.  Sometimes people feed hay at 8pm, and no-one goes out to the barn to feed again until 5am in the morning.  The hay fed at night is all eaten by 10pm and the horse goes for a long time without eating.  Some of the new slow-feed hay nets can stretch out the meal time.  You can give the same amount of hay, but it takes the horse longer to eat it, and there will be feed in his stomach longer.”

Feeding lower-starch food is also helpful, to prevent ulcers.  Feeding fat can make up the needed calories.

“Sport horse people picked up on this more quickly, feeding a low-carb / high-fat concentrate.  Many thoroughbred people still want to feed a high-carbohydrate / high-grain diet.  This inherently puts the horse at greater risk for colic and gastric ulcers.  The GI tract is not designed to handle a high-starch diet.  The small intestine becomes overwhelmed; it cannot extract that much carbohydrate quickly enough, and some of it goes on into the hindgut-with potential problems.

“Part of ulcer prevention can include feeding a lower carbohydrate diet.  It can be high in fat, so it still provides calories, but we try to limit the starches.  High-carbohydrate feeds increase volatile fatty acids in the stomach, which can be irritating to the non-glandular mucosa.

“I’d like to do more research to see how much of a difference a little fibre might make and how much would it truly reduce the risk of horses getting ulcers.”