E159
 Digestive Tract Problems
Esophagus, Stomach, Intestines, and Colon

choke | strictures and compressions | ulcers | colic | enteroliths | sand impactions

Introduction: The digestive tract of a horse begins with the horse’s mouth and ends with the large colon. All of the structures between these two points play an essential role in the consumption, breakdown, and utilization of feed. Horses, like pigs and humans, are considered simple stomach animals, meaning that their stomachs have only one major compartment. When all the structures in the horse’s digestive tract are functioning properly, the horse is able to gather the necessary nutrients to sustain life; however, problems with anything from the teeth to the intestines can cause weight loss, nutritional deficiencies, and even colic. The following information will identify some of the more common problems associated with the digestive tract of a horse. The information will start with the esophagus; however, it is important to remember that the lips, teeth, tongue, and epiglottis all have specific duties in properly acquiring, grinding, and then presenting food to the esophagus.

Problems in the Esophagus

Introduction: The esophagus is the tubular structure that connects the back of the throat to the stomach. It is made of muscle tissue that can expand as different sized feed material moves through it.

  1. Choke: The term choke refers to a blockage of the esophagus. The blockage in the esophagus is often made up of feed material (grain, hays, pelleted feeds, corn cobs, etc.) that becomes impacted. Horses that do not chew their food properly due to poor teeth or after being sedated are at an increased risk for developing this problem.

    Clinical Signs:     A horse suffering from a choke problem will often extend its neck, be anxious, and make multiple attempts to swallow. Because the feed material and saliva cannot get to the stomach, the horse will often have excessive saliva and discharge coming out of the mouth and the nose. This discharge is often green in color because it contains feed material.

    Treatment:     Once this problem is noticed, it is best to remove the horse from any feed and water. A veterinarian should be called and treatment started as soon as possible. At first the horse is often given a sedative such as xylazine to help lower the horse’s head, relieve some of the pain, and provide some muscle relaxation. With the head lowered, a naso-gastric tube is often placed to determine the location of the blockage and see if the blockage can be gently removed. Sometimes water is flushed into the tube to help dislodge the obstruction. All of these procedures should be done with care to prevent rupturing the esophagus or having the horse accidently aspirate some of the water or feed material into the lungs. With time, patience, and a little luck, many blockages are relieved.

    If the blockage was present for longer than just a few hours, the horse should be held off feed for 24-48 hours to help rest the esophagus. When food is given, it should be made into a slurry or soaked down with water to aid in its consumption and progress down the esophagus. In severe cases, an endoscopy instrument can sometimes be used to help remove the blockage and evaluate the condition of the esophagus after the blockage is removed.

    Prevention:     To help prevent choke problems, the following items should be addressed:
    1. Always have the horse’s teeth in good condition for proper grinding of feed material. This may mean having the teeth floated on a yearly basis. Older horses with poor teeth may need to be fed a soft diet that requires less chewing. Some diets may need to be watered down for easier consumption.
    2. Always provide the horse with plenty of water. This will help the horse produce plenty of saliva to lubricate the feed as it goes down.
    3. Eliminate any situations where the horse may be in competition with other horses during feeding. Competition may cause one animal to rapidly engulf their food, without chewing it properly. Also allow the horse plenty of time to consume its ration.
    4. Many veterinarians do not recommend feeding a horse while it is being trailered. Feeding a horse while it is being trailered has been associated with choke in animals that do not chew their food properly.
    5. After a horse has been sedated for any reason, remove all feed. A horse under mild sedation will not grind the feed and is prone to choke. After the horse is fully awake, feed can be given.
       
  2. Strictures and Compressions:
    1. Stricture: Any type of injury or irritation to the esophagus can result in a narrowing or stricture at that site. This narrowing of the esophagus causes the horse to be prone to choke. Sometimes the strictures are the result of surgical attempts to repair a problem in the esophagus or are the result of previous choke episodes. Animals diagnosed with this problem can be fed soft to almost slurry type pelleted diets. If this is not successful, difficult surgical repair can sometimes help.
       
    2. Compressions: Enlarged lymph nodes or abscesses in the neck region can cause compression of the esophagus. This compression often causes the horse to choke. In some cases, the enlarged lymph nodes are the result of a strangles infection. When these compressions are the result of enlarged lymph nodes, treatment should focus on reducing the size of the lymph nodes as quickly as possible.
       
  3. Esophagitis: This term means inflammation of the esophagus. Esophagitis can be caused by stomach acid reflux or chemical irritation. A horse with this problem may appear to be in pain when it is eating and swallowing. If the problem continues, the horse may go off feed completely. To diagnose esophagitis, an endoscopic exam must be performed. The lining of the esophagus will appear red, inflamed, and sometimes ulcerated. Treatment for this condition depends on the cause. For example, the cause for acid reflux is often a blockage that prevents material from exiting the stomach. In these cases, the blockage must be corrected and products such as cimetidine and ranitidine can be used to reduce stomach acid production. In all cases of esophagitis, the esophagus should be rested. This may mean feeding only soft, slurry type feed mixtures in more mild cases, or not feeding the horse any solid feed for several days in severe cases.

     

Problems in the Stomach, Intestines, and Colon
  1. Ulcers
    Introduction/Causative Agents:     Gastric or stomach ulcers are considered to be very common in foals and adult horses. Some studies indicate that as many as 50% of all horses have ulcers. Race horses, horses kept and fed in a stall environment, and horses that are sick are at an increased risk for developing ulcers. Animals that are fed a high concentrate diet or forced to go a period of time without eating are also at a higher risk of developing ulcers. Hospitalization, particularly in foals, can also contribute to ulcer development. All of these things tend to increase the amount of stress placed on the horse causing blood to be circulated away from the stomach. Blood not reaching the stomach, along with any source of stress (illness, training, etc.) that causes the horse to decrease the amount of food it consumes, can cause ulcers. There are also many medications, such as aspirin, phenylbutazone, and flunixin (Banamine), which can lead to ulcer development if given in excessive doses or for extended periods of time. Foals are also susceptible to developing ulcers in part of the small intestine called the duodenum.

    Clinical Signs:
    In Foals    : The majority of foals with ulcers may not show any noticeable signs. When signs do occur, the foal will often experience colic (rolling, laying on its back), increased salivation, and grind its teeth (bruxism). The foal may also show signs of poor growth and have a rough hair coat. The foal may not want to nurse or eat.

    In Adults    : Some adult animals that have ulcers will often have repeated colic episodes, have a decreased appetite, have a tense abdomen, and be in poor body condition. Certain horses may not perform well, experience a change of attitude, and simply "not act right." In many cases, these signs are very subtle and often go unnoticed.

    Diagnosis:     The most reliable way of diagnosing this problem is through an endoscopic examination of the stomach. During the exam, ulcers can be readily identified. If an endoscopic exam will not be performed on a horse suspected of having an ulcer, a diagnosis can be made based on clinical signs and then a positive response to ulcer treatment.

    Treatment/Prevention:     The key to treating any ulcer is to try and decrease the amount of acid in the stomach and remove whatever stress is currently being placed on the horse. Acid-reducing medications such as cimetidine (Tagamet - page H800) and ranitidine (Zantac - page H993), can be excellent treatments. Many horses will respond positively to these treatments by eating more and not showing signs of colic within 48 hours. The acid-blockers should be given for at least 14-21 days. Antacids such as Maalox (380 mLs every 4 hours) or Mylanta (240 mLs every 4 hours) can also be given in high doses. Sucralfate (Carafate - page H792), a protector for the ulcer against the acid, can also be given, but works better in foals.

    In addition to the medications, management changes should also be made in the horse’s life. If possible, the horse should be placed on pasture. Horses that cannot be placed on pasture should have plenty of long-stem hay available at very regular intervals throughout the day. All concentrates should be eliminated. Training and any other stresses (surgery, weaning, etc.) should be postponed. Horses that are sick should be treated aggressively and then be returned to their normal environment as soon as possible. Doses of anti-inflammatory medications such as phenylbutazone and flunixin (Banamine) should be used according to label and veterinary directions. Acid-reducing medications may also be considered as a preventative in race horses and animals that are involved in heavy training programs.
     
  2. Colic: The term colic is used to describe pain that originates from the abdomen. It can be caused by many different things including ulcers, obstructions, worm (ascarid) impactions, hernias, tumors that entrap bowel, and twists in different sections of the intestines. Almost every horse owner, at one time or another, will have a horse that colics. Colic should be considered a potentially life-threatening problem that requires immediate attention. The information on page E120 of this manual gives details on what clinical signs a horse may show when it colics. Page E120 also contains information on how to determine if the horse needs veterinary attention. The following gives some details about the common causes of colic.
    1. Impactions: An impaction is something inside the bowel that blocks the normal flow of feed material through the intestines or colon. It can occur almost anywhere along the intestinal tract. Things inside the intestinal tract such as worms, feed material, foreign objects, sand, and enteroliths can cause the impaction.

      Enteroliths       are extremely hard objects that are formed inside the colon when layer upon layer of magnesium ammonium phosphate is placed over a bit of hair, a foreign object, or a small stone. The layers of magnesium ammonium phosphate accumulate over time to form an enterolith that can readily block the bowel. The following are some ideas to help prevent enterolith formation:
      • Do not feed horses on the ground where they can pick up foreign objects (sand, pebbles, plastic, twine, etc.) that may contribute to the formation of an enterolith.
      • Replace diets that are high in alfalfa with oat or grass hay. Studies show that horses fed diets that contain greater than 50% alfalfa hay are more susceptible to enteroliths.
      • Feed less bran in the horse’s diet. Bran contains high levels of phosphorus that may aid in enterolith formation.
      • Feed more grain to the horse. This will decrease the pH level in the intestinal tract. Studies show that horses with a high intestinal pH have an increased chance of developing enteroliths.
      • Provide plenty of exercise for the horse. Horses that are confined to a stall and lack daily exercise have decreased intestinal contractions. This can also contribute to enterolith formation.
      • Feed the horse 3-4 times a day. This can increase the passage of feed through the intestinal tract and reduce the chance for enterolith formation.

        Many of the above suggestions about preventing enteroliths were taken from UC Davis, The Horse Report Vol 16 (1), March 1998.

      Sand Impactions: Horses that consume sand repeatedly are at risk of developing sand colic or a sand impaction. In addition to developing colic, horses that consume sand are also prone to diarrhea. Horses that suffer from sand colic are in pain and may have decreased gut sounds and manure production. Horses that suffer from sand impactions can be diagnosed during a rectal palpation by a veterinarian. If the impaction is severe, the veterinarian may administer laxative agents, analgesics, and fluids (either intravenous or oral).

      Prevent sand colic problems by feeding horses psyllium and not letting them eat directly on the ground. The recommended amount of psyllium is about 0.5 kg or 1 pound of psyllium 2-3 times a day. Details about determining if a horse is consuming excessive amounts of sand can be found on page B740 of the Equine Manual.
       
      2.
    2. Obstructions: An obstruction is similar to an impaction in the sense that the normal flow of feed material through the intestines or colon is blocked. The obstruction can be caused by abnormal movements the bowel makes such as a displacement, twist (volvulus), or intussusception. Other blockages are caused by something else in the abdomen that entraps or entangles a section of bowel. Examples of things that can entrap the intestines include a fat (lipoma) tumor and herniation of a section of the bowel into the inguinal canal, the umbilical area, or through the diaphragm. When a section of the intestines or colon twists or is entrapped, a blockage occurs and the blood supply to and away from the area is severely compromised. These horses may suffer severe pain, and the section of bowel that is involved will deteriorate rapidly without the proper blood supply. A twist or volvulus of the intestines or colon may be associated with changes in the diet, internal parasites, and giving birth.

      An intussusception occurs when one short section of bowel moves inside of an adjacent section of bowel. This commonly happens when the bowel is irritated and the motility (movement and contractions) of the bowel is compromised. Things such as parasites, diet changes, foreign bodies, and previous surgery can decrease bowel motility. Horses that have an intussusception will often not appear to be in great pain unless the intussusception causes a complete blockage.
       
    Colic Treatment: All of these colic problems cause the horse varying levels of pain and can result in the necrosis (death) of the section of the bowel that is involved. Many of these problems will resolve on their own with the administration of conservative treatments such as mineral oil, analgesics (Banamine), and fluids. Other problems will not resolve unless surgery is performed. Without a thorough exam performed by a veterinarian it is virtually impossible to determine the exact cause for the colic. Even after the exam and additional diagnostics, many causes of colic will not be identified until surgery is performed. Page E120 contains additional treatment information.

Selected references:
Smith, Bradford P. Large Animal Internal Medicine. St. Louis: Mosby 1996: 679-788.