Gastric Ulceration in Adult Horses
If you've ever had gastric ulcers or even just bad heartburn, you can sympathize with your horse when he has one of the most common health problems of the stabled horse – gastric ulceration. We humans have the luxury of a quick trip to the drug store for our favorite heartburn remedy, and we can call our physicians for a more in-depth diagnosis of why we experience such agonizing gastrointestinal pain. But horses can only show us by indirect signs that they are in chronic, debilitating pain. How can you understand the signals that your horse is sending you, and understand why he is sending you those signals?
Gastric ulceration in any species refers to an erosion, or sloughing, of one or multiple areas of the surface layer of the stomach. Gastric ulceration is common in horses – in various studies, from 70 percent to 100 percent of horses examined had endoscopic evidence of gastric ulceration. This, however, does not mean that all of these horses had clinical signs of gastric ulceration.
Unlike people, who can develop gastric ulcers in response to a bacterial infection, no infectious cause of gastric ulceration has been identified in horses. In fact, few specific causes of gastric ulceration have been clearly identified. However, most practitioners recognize that stress seems to precipitate gastric ulceration in foals; and infrequent feeds of low-roughage, high carbohydrate foods and a high level of training have been implicated in adult horses.
Unlike humans, horses secrete gastric acid continuously, whether they are eating or not. In the wild, horses spend the majority of their days continually eating small amounts of relatively poor quality, high roughage food. Continual acid secretion accommodates this natural lifestyle perfectly. When horses are fed large quantities of high quality food infrequently, their stomachs empty rapidly, essentially leaving the stomach with nothing to do.
The stomach has a variety of protectant factors against the effects of gastric acid, but when the stomach is empty, the horse's ability to withstand the effects of gastric acid can be overwhelmed. If gastric ulceration becomes severe, the erosions may begin to bleed. Horses can eventually become anemic and low in protein due to losses through the gastric ulcers.
The use of certain anti-inflammatory drugs (such as phenylbutazone ('Bute') or flunixin meglumine (Banamine™) can also induce gastric ulcers in horses.
What to Watch For
- Recurrent colic
- Acute colic
- Decreased appetite
- Decreased manure production
- Poor body condition
- Poor haircoat
- Poor performance
Your veterinarian will take a thorough history to try to identify any risk factors that may have contributed to your horse developing gastric ulceration. In addition, the following may also be necessary:
- A thorough physical examination. Horses that exhibit symptoms of feed refusal, colic after feeding, weight loss, and do not have a fever, are the usual suspects.
- A work-up for colic. If your horse has been showing signs of colic, your veterinarian may choose to perform a work-up for colic, including passing a nasogastric tube and performing a rectal examination to look for signs of intestinal distention or displacement.
- Blood tests. Your veterinarian may also choose to take blood tests to make sure that your horse is not anemic or suffering from kidney problems.
- Gastroscopy. This is the only way to definitively diagnose gastric ulceration. Gastroscopy refers to the use of a specialized endoscope – a fiberoptic instrument – that essentially allows the use of a camera to visualize the interior of the stomach. Your veterinarian will look for areas of the stomach lining that have an abnormal appearance – this may range from outright areas of bleeding to areas of eroded or thinned tissue.
If your horse has gastric ulceration, your veterinarian will choose to treat with one of a variety of drugs that decrease the acidity of the stomach. He or she will be able to make dietary and training recommendations.
It is important to follow all the instructions given by your veterinarian concerning length and frequency of administration of drugs. Make sure that your horse actually consumes the medications recommended by your veterinarian; it won't help if medications are left in a little pile in the bottom of the feed tub. For some picky eaters, it may be necessary to mix the medication with molasses or applesauce, and syringe it into the mouth.
It is important to monitor your horse's appetite, manure production, and attitude. Most horses will require a high roughage diet and plenty of turnout for best resolution of gastric ulceration.
Horses that have constant access to turnout and roughage in the form of hay or pasture, and horses that are not in training, rarely develop gastric ulceration.
Probably, the best prevention for gastric ulceration is to mimic, as best as possible, the life of a horse at free range. This translates into frequent small meals, a preponderance of roughage in the diet, and plenty of turnout.
- It is important to remember that horses are herbivores, meaning that they are true vegetarians. Consequently, the anatomy and physiology of their gastrointestinal system is much different from ours.
- It is also important to remember that horses have very small stomachs when you consider their size – only approximately 4 gallons at holding capacity. This, again, reflects the way that they would eat in the wild – very frequent small meals, so that the stomach is never stretched to full capacity.
- To start with, the horse's stomach is made up of two different parts. The primary difference between these two parts is that they have different types of cells lining them. Epithelium is a general term for the covering of any surface of the body, and it consists of many cells tightly joined to each other.
- The first type of epithelium encountered in the stomach is stratified squamous epithelium, after which a glandular epithelium is found. A distinct margin, called the margo plicatus, separates the two.
- The glandular epithelium, as its name suggests, contains many glands that produce gastric secretions. The squamous epithelium contains no glands, and merely serves to contain food, without aiding in any chemical digestion.
- The purpose of the stomach is to help in the long process of digesting food. In order to do this, the stomach must not only mix food, but produce secretions that help to break down food.
- Two digestive factors, hydrochloric acid (gastric acid) and pepsin, are produced in the glandular portion of the stomach. Both hydrochloric acid and pepsin begin the digestive process in the stomach before food reaches the small intestine.
- The glandular portion of the stomach also secretes factors that help to protect the stomach. One of these, a mucus-bicarbonate layer serves to protect the stomach lining both by preventing acid from physical contact with the stomach surface, and by buffering gastric acid at the level of the stomach lining .
- This mucous-bicarbonate layer protects only the glandular portion of the stomach, and not the squamous portion.
- Other protective factors include -prostaglandin E, which causes increased blood flow in the stomach lining, increased secretion of the mucus-bicarbonate layer, and also causes decreases in hydrochloric acid production -various growth factors
- Unlike humans, horses produce gastric acid continually, regardless of whether they are eating regularly. If horses do not eat, then their stomachs become more and more acidic because acid production cannot be 'turned-off'.
- The squamous portion of the stomach is at the greatest risk from increased acid production, because it does not benefit from all the protective factors that the glandular portion of the stomach enjoys.
Gastric ulceration in horses occurs when acid production overwhelms the protective factors. Unlike the situation in humans, there is no evidence at this point that there is a bacterial cause of gastric ulceration in horses.
Acid production may overwhelm the stomach for various reasons, including:
- Infrequent, low-roughage feeding that leaves the stomach empty the majority of the time. This provides a window of opportunity for gastric acid to erode the stomach lining.
- Intensive training, which tends to go hand-in-hand with infrequent turnout and low-roughage, high-concentrate feeding.
- Administration of NSAIDs (non-steroidal anti-inflammatory drugs)
How do NSAIDs cause gastric ulceration?
- NSAIDs interrupt the production of prostaglandins, which are a diverse family of molecules with extremely diverse effects. You can thank prostaglandins for keeping the blood flowing properly in portions of your kidney, and you can also blame- and thank- prostaglandins for stimulating uterine contractions during childbirth, and for giving you a fever when you have a good case of the flu. By blocking the production of prostaglandins, NSAIDs help to decrease fevers, aches, and pains.
- Common NSAIDs given to horses include Banamine™ and Bute (phenylbutazone). As with human beings, NSAIDs are given to treat gastrointestinal pain associated with colic, reduce fever, and to treat inflammation and pain in the musculoskeletal system. Anyone who has had a horse with colic can attest to the efficacy of Banamine™ in decreasing gastrointestinal pain in horses!
- One particular prostaglandin, called PgE2, plays an important role in preventing gastric ulceration. PgE2 does this by decreasing gastric acid production as well as by increasing blood flow to the gastric epithelium.
- Unfortunately, the NSAIDs that are commonly used in horses don't know that we would like to decrease pain, but retain appropriate blood flow to the stomach. Consequently, we refer to them as non-specific inhibitors of prostaglandins. When we use them to decrease fever, for instance, we also interfere with normal gastric function. The results are multiple – the horse's stomach becomes more acidic, and this contributes to the development of gastric ulceration. Normal blood flow is necessary to healing, and so disruption of normal blood flow leads to a double whammy – not only does the horse develop gastric ulcers, but he also can't heal them very well. It's a vicious cycle. (NSAIDs can also have a deleterious effect on the kidneys, but that is another story).
What are the signs of gastric ulceration in the horse?
Signs of gastric ulceration can be quite hard to pinpoint in horses. Imagine if you couldn't use words to describe how you feel when you have heartburn – you would have to use body language to try to explain the problem. That body language might include lying down more frequently because you're in pain, but then you'd get up again because lying down can make the pain worse. You wouldn't want to eat the foods that you previously enjoyed (even though that might have been a cheeseburger and fries!). You might start to eat, and then stop, because eating makes the pain worse. If you stopped eating the things that are good for you, you might start to lose the gloss in you hair, or become too thin, because you are no longer getting the nutrients that you need. If the pain became intense, you might groan, and hold your abdomen. Well, horses do many of these things, and more.
The most common signs of gastric ulceration in horses include:
- Mild, chronic colic – horses may occasionally look at their sides, lie down more frequently, play with their water, or paw, particularly after eating. A common, and appropriate treatment for mild colic are NSAIDs. However, as we discussed above, NSAIDs themselves can induce gastric ulcers by decreasing blood flow to the stomach and increasing the acidity of the stomach. Without realizing it, you and your horse may have entered a classic vicious circle – the more frequently he has episodes of colic because of the ulcers, the more often he is given NSAIDS – and the ulcers just get worse.
- Less frequently, horses may suffer an acute, severe bout of colic that causes them to really get down on the ground and belly-ache.
- Poor condition, especially moderate weight loss. In a typical 1000 pound horse, this usually means weight loss of between 25-75 pounds. This might result in you being able easily to see your horse's ribs. If your horse was on the lean side to start with, with weight loss you might be able to see his hip bones, and his neck may start to look thin and stringy. Because of decreased nutrient intake, your horse might have a coat that looks dull.
- Decreased appetite – horses are often reported to eat their hay, but not their grain. Hay takes longer to digest and clear the stomach, so this naturally helps to buffer what is in the horse's stomach. Hay also needs more chewing, and chewing helps to produce more saliva. Saliva is a natural buffer of acids, so, again, this may alleviate some ulcer symptoms.
- Decreased manure production – this is usually related to a decreased appetite, and perhaps to decreased gastrointestinal motility.
- Poor performance – this may stem from pain. In severe cases, where the gastric ulcers are bleeding, this may also be due to anemia (low red blood cell count).
- Signs of gastric ulceration may also be as vague as a change of character, or a 'crabby attitude'. This isn't very hard to understand! Chronic pain is enough to make any horse less cheerful about his work.
- As always, your veterinarian will take a thorough medical history. Remember that your veterinarian usually won't know at first that the problem is gastric ulceration – rather, she will be examining your horse because you have told her that your horse is showing one of the symptoms that are listed above. This means that your veterinarian is usually asking questions to figure out why your horse is showing intermittent signs of colic or isn't 'quite himself'. Your veterinarian will probably question you about your horse's work schedule, feeding schedule, and deworming schedule. If your horse has been colicky, your veterinarian will want to know how many times he has colicked, how long each bout lasted, how severe the signs of pain were, and what your horse was treated with.
- Your veterinarian will always perform a good physical examination, including taking your horse's temperature, and listening to his heart and lungs with a stethoscope.
- If your horse has been colicky, your veterinarian will extend the physical examination, and include palpation per rectum (a 'rectal'). When your veterinarian performs a rectal, she is looking for any abnormalities in the position, size, or consistency of the internal organs. She will be particularly alert for abnormalities that could explain intermittent colic, such as an enterolith (a stone that can form in the large intestines), or thickening of the bowel that might indicate inflammatory bowel disease. Your veterinarian may wish to pass a nasogastric tube to make sure that your horse doesn't have excessive fluid in his stomach.
- Depending on the signs that your horse is showing, your veterinarian will pursue various diagnostic tests.
- If your horse has lost weight or has chronic colic, your veterinarian will probably do a thorough oral examination to see if poor dentition is contributing to the problem. Your veterinarian will want to know how your horse's appetite has been, and will probably want to look at your hay, grain, and pasture. Your veterinarian will probably also perform a fecal float to determine if your horse is carrying a high parasite burden.
- If your horse has been showing chronic signs – whether that be colic, poor performance, or weight loss – your veterinarian will probably want to do bloodwork. A complete blood count, or CBC, looks both for evidence of inflammation or infection, and for evidence of anemia. If your horse has a high white cell count, or a high fibrinogen level (this is a protein that is found in the blood in the presence of inflammation or infection), then your veterinarian might suspect an infectious or inflammatory process. If your horse has a low red blood cell count, then your veterinarian will diagnose anemia.
- Anemia can have many causes: gastric ulceration can make horses anemic due to actual blood loss from the ulcerated areas. Anemia can contribute to poor performance by making your horse feel weak. The red blood cells carry oxygen, which is the body's ultimate fuel. If there aren't enough red blood cells to carry adequate amounts of oxygen, then your horse will start to feel as though he is 'out of gas' when he goes to exert himself.
- Because horses have extremely long digestive systems (at least 72 feet of small bowel alone!), most veterinarians agree that there isn't much use in looking for traces of blood in the feces, or fecal occult blood.
- If, after extensive examination, your veterinarian decides that the medical history and physical examination findings are very suggestive of gastric ulceration, the definitive way to diagnose gastric ulceration is with a very long endoscope, known as a gastroscope. This allows us to place a camera inside the horse's stomach, and thus get a close-up view of the stomach lining. The type of endoscope that is commonly used to look at a horse's upper airways simply won't do – it isn't long enough. In order to visualize the adult horses stomach, an endoscope that is at least 210 cm long is necessary. That translates to 6.9 feet! In order to obtain a good view of the stomach, it is important for the stomach to be empty. That's why your veterinarian will usually ask you to keep your horse from eating for 18-24 hours before the gastroscopic examination. Your horse will still be able to drink during this time.
- Although most of the time, your horse will have to undergo gastroscopy at a hospital for specialists, more and more veterinarians in the field are purchasing the appropriate equipment to do so. The procedure will be the same either way.
- In order to do a gastroscopic examination, your veterinarian must pass the scope through the nostrils, into the pharynx (area just before the esophagus, or swallowing tube), and then into the esophagus, and, finally, into the stomach. Although gastroscopy isn't painful to the horse, most horses do resent anything being passed through the nostrils. The anxiety can be diminished considerably by giving the horse a tranquilizer – usually xylazine or a combination of xylazine and another drug. Long 'scopes' with the ability to see all the way into the stomach are extremely expensive, and your veterinarian will be anxious to keep your horse from chewing on it in case it doubles up and goes back into the mouth (yes, this does happen!). For this reason, usually a short plastic tube (similar to, but much shorter than the tube that is used for deworming your horse), is first passed through the horse's nose and into the esophagus, and then the scope is passed through that shorter tube.
- Gastroscopy itself doesn't take very long – only approximately 15-20 minutes. Because the stomach is a collapsible organ, it must often be pumped up with air during the examination so that every bit of the surface can be seen.
- Typical findings include areas of the stomach that are eroded, thinning, bleeding, or have abnormal amounts of scar tissue.
- After the gastroscopic examination is finished, all the air will be let out of your horse's stomach to avoid colic. Then, your horse will still be kept off any food until he seems to have fully woken from the tranquilizer.
The goal of treatment is to decrease the level of acidity in the stomach in order to allow the horse's natural healing processes to mend the ulcers. There are several ways to achieve this goal: all of them center around addressing the situation that allowed your horse to develop gastric ulceration in the first place. The way that you and your veterinarian choose to treat gastric ulceration will usually depend on your schedule as well as your ability to change your horse's environment.
Most horses do require some drug therapy in order to successfully treat gastric ulcers. Drugs designed to treat gastric ulcers may decrease the amount of acid produced by the stomach, physically coat the stomach to prevent the acid from wreaking havoc or buffer the acid in the stomach.
Drugs that decrease the amount of acid produced by the stomach
- H-2 blockers. These drugs block histamine, one of the factors that stimulates acid production. They reduce the signals to the acid-producing cells, so that they slow down their rate of acid production. Drugs that fall into this category include cimetidine, ranitidine, and famotidine. All of these are available as over-the-counter drugs for humans, albeit in much smaller concentrations than are suitable for a horse! Most of them must be given three times a day for them to work properly.
- The most commonly used drug that blocks acid from getting access to the stomach lining is sucralfate. Sucralfate, however, is best for helping to heal ulcers in the glandular mucosa, and most adult horses have ulcers in the squamous mucosa. For this reason, it is not suitable for use on its own in treating gastric ulcers in adult horses.
Drugs that buffer acid
- Antacids are commonly used in humans, and some veterinarians advocate using them in horses. Antacids can buffer an adult horse's stomach, however, the effect lasts for less than an hour, and very large volumes (over 1/3rd of a pint) must be used.