by Dr. Joe D. Pagan and Dr. Peter Huntington
Every horse owner appreciates the delicate nature of the equine gut, with colic being a major fear. Problems related to the small intestine and large intestine causing colic are well understood and routinely treated. What may be surprising to many is how often the stomach is affected and the incidence of gastric ulcers is extremely high, particularly in performance horses.
Research done in Hong Kong, the USA and clinical studies in Australia has clearly shown that as many as 80 to 90% active racehorses are victims of an insidious problem that can affect their performance, gastric ulcers. A surprising number of ulcers have also been discovered in other performance horses (up to 60%) such as those involved in eventing, showing and western competition. In performance horses, there is an association between ulceration and nervousness, but it is unclear whether this is a cause or effect. Ulcers have been long recognized as a problem in foals, particularly those that are sick for some other reason. It is predicted that most domesticated horses will have ulcers at some point in their lives. This condition may not cause any observable problems in some horses but ulcers can also be both painful and costly. However it is something that can be helped, and possibly even eliminated in some horses with proper management.
Why Ulcers Form
The majority of equine ulcers form in the upper portion of the stomach that is comprised mainly of lining cells similar to those found in the oesophagus. This section of the stomach, which serves as a reservoir for ingesta to keep the lower stomach from being overwhelmed, has little protection from the secretions produced in the lower part of the stomach (hydrochloric acid and pepsin) that help to break down ingested food. While the lower glandular section of the stomach has buffers and a mucous lining to help protect it, the whole system is in a delicate balance. This balance can be thrown off by a change in eating habits, feeds, and possibly exercise-induced stresses. Most horses, allowed the opportunity to free-range graze, rarely have a problem with ulcers, as the equine gastric system evolved to accommodate this type of eating behavior. However, many performance and pleasure horses are not routinely given the opportunity to graze at will or even eat hay all day. This sets the stage for irritating substances from the lower stomach to invade the upper regions and create problems that can range from heartburn to serious problems. Research has shown that equine gastric ulcers are not caused by Helicobactor pylori bacteria which are a common cause of ulcers in humans.
Foals develop ulcers when their stomachs produce more acid than their mother’s milk can negate. When a foal experiences physiological problems and diseases such as diarrhea or the stress of separation from its dam, the acid buildup in the stomach can cause serious problems, including perforating ulcers that can lead to death. Ulcers can occur in normal foals but clinically significant ulcers can be related to stress or factors that reduce milk intake, such as disease. As the foal ages and begins to graze, these problems lessen because the grass or hay in the upper portion of the stomach provides the necessary buffer.
Research on feeding programs and their effects on ulcers in stall-bound horses have shown that animals with a continual source of hay have significantly lower acid levels in their stomachs. This is to be expected as forage consumption stimulates saliva production and saliva helps to protect the upper region of the stomach. Conversely, horses that have had feed withheld for 24 hours have a much greater level of acid in their stomachs. In a study done in Virginia, bleeding ulcers were induced in horses within three to seven days following a feeding regimen of a 24-hour fast followed by a feed followed by another 24-hour fast.
Stress may also be a factor in the development of ulcers in horses. Weanlings almost always have the opportunity to graze at pasture, yet large numbers of weanlings develop ulcers. As studies have shown, many racehorses have ulcers, so there is some concern that training stress may be a contributing factor. Horses in training have very different feeding programs from those allowed the opportunity to graze freely. Most horses in training are confined for a great portion of the day and are fed large grain meals, a practice which increases the production of gastrin, a hormone that stimulates gastric acid. Studies have also shown that horses produce twice as much saliva when eating hay as they do eating grain, so grain does not have the beneficial effects of free-choice hay. But, even racehorses provided with a constant supply of hay seem more prone to ulcers. The stressful rigors of hard training or travel may indeed be a causative factor in the incidence of gastric ulcers in horses. One study showed that were galloped on a treadmill had a much higher incidence of ulcers than horses on the same feeding program that were doing slow trotting work.
Signs of Gastric Ulcers
Many foals and horses with ulcers show no outward signs, but others may show some of the signs listed below. The severity of ulcers can range from mild to severe and in foals, signs such as salivation and teeth grinding are seen with severe ulceration. However mild ulceration has been associated with a loss of performance. There are lots of other causes of these sort of signs so you should consult your veterinarian if your horse shows these sort of symptoms or you suspect it has ulcers. Clinical studies of racehorses have shown that 40% horses with ulcers will show some of the signs associated with ulceration, but there is no direct correlation in the signs and severity of ulceration. Some performance horses don’t show any signs, but do respond to treatment by increasing appetite and condition.
Table 1: Signs of gastric ulceration in horses and foals
- Picky eater
- Weight loss or poor condition
- Dull or sour attitude
- Rough hair coat
- Lack of ‘attention’
- Trains off
- Drop in performance
- Lying on back – foals
- Salivation – foals
- Diarrhoea – foals
- Teeth grinding – foals
An endoscopic examination of the stomach is needed to definitively diagnose gastric ulceration, but few vets have long enough endoscopes to gain access to the stomach of an adult horse so the diagnosis based on clinical signs or response to treatment is often made.
Preventing and Treating Ulcers
In foals it is important to reduce stresses and many people put sick foals that aren’t drinking well, on ulcer treatment to prevent development of ulcers. Obviously, providing horses with the opportunity to free-range graze or, failing that, to have access to free-choice hay would be the best way to keep horses from suffering the effects of acid buildup in the gut. This, however, is not always possible, particularly for horses in heavy training or those that are easy keepers. Time spent eating forage such as grass, chaff and hay seems to be a critical factor.
In stabled horses, you should try to alter the feeding schedule to mimic a grazing situation by giving the horse access to hay at all times. Recent studies have shown that compared to a grass hay diet, a diet of lucerne hay and grain provided greater buffering of gastric acidity. Therefore, it is recommended that you include some lucerne in the diet, perhaps by mixing chaff with grain.
Also take advantage of the horse’s natural buffering mechanisms. Where available, provide the horse as much pasture turnout as possible. Even large yard turnout is better than stall confinement. The horse will get a little more exercise and will no doubt have a better attitude. Instead of two meals per day, feed smaller concentrate meals at more frequent intervals and include chaff to slow down grain intake and increase saliva production. Reducing grain intake by the addition of calories from fat and maximizing the intake of forage will also help. If grazing is not available, including an equine antacid such as Neigh Lox in the diet might help buffer gastric acidity.
If a horse with ulcers is spelled on a high forage diet, many heal spontaneously in a month. Treating ulcers involves either inhibiting gastric acid secretion or neutralizing the acid produced. Three classes of drugs can be used to inhibit gastric acid secretion: histamine type-2 antagonists such as cimetidine (Tagamet) and ranitidine (Zantac or Ulcerguard); proton pump inhibitors such as omeprazole (Gastroguard); and prostaglandin analogues. These drugs are highly effective in curing gastric ulcers in 3 to 4 weeks in horses, but they are also very expensive. A response to treatment will be better when the horse is spelled from work and is in a paddock, but this is often not practical. Lower doses may be effective in preventing recurrence, because if ulcers are treated and the horse stays in work then they usually recur quickly. In addition ranitidine has a 3 day withholding period prior to racing. Omeprazole is not yet available in Australia. Less expensive versions of these drugs have been marketed as compounded ulcer medications, but research has shown these to be less effective.
An alternative to suppression of acid production is to neutralize stomach acid and protect the squamous mucosa from exposure to acid. Antacids may be a good preventative tool and can offer the horse some symptomatic relief of the discomfort associated with ulcers. Human antacids need to be given frequently in large volumes by stomach tube and may have adverse side effects such as inco-ordination. Neigh-Lox is a product marketed by Kentucky Equine Research and is available through veterinarians and selected other suppliers. Neigh-Lox’s concentrated pelleted form allows it to be fed daily mixed with the normal grain ration, or given just prior to work. It has been shown to neutralize gastric acid as well as to protect and preserve the stomach lining from continuous overexposure to gastric acid. The product is safe for use in horses from foals and weanlings to performance horses and breeding stock. Unlike other agents, there is no need to withhold use of Neigh Lox prior to racing. Preventative maintenance is considerably less expensive than the drugs used to cure the ulcers once they have occurred.
Dr. Joe D. Pagan and Dr Peter Huntington,
Kentucky Equine Research
Brighton, Victoria, Australia