From Esophagus to Stomach
By Eleanor Blazer
Through the lips, over the gums, look out stomach––here it comes! Once the horse has sorted, chewed and softened feed with saliva, he swallows. The slurry travels down the esophagus and into the stomach. The esophagus, a muscular tube about 50 inches long in the average horse, leads to the stomach.
A horse chokes if a foreign object blocks the esophagus. This object may be an apple, corn cob, hay cube, a wad of improperly chewed feed or even baler twine. Horses can choke on almost anything!
The equine esophagus can also be blocked by a growth (tumor) or scar tissue from trauma (a previous choke episode or damage to the sensitive tissue because of a medical procedure).
Symptoms of choke in horses:
• Heavy nasal discharge that contains bits of feed and white foamy saliva
• Excessive salivation
• Stretching and extending the neck
• Attempts to retch
• Inability to swallow
• Coughing and blowing out feed through the mouth and nose
Call your veterinarian and remove all feed as soon as you see any of these symptoms. Even though the horse can still breathe, this is a medical emergency. Prolonged obstruction can cause scar tissue. Aspiration of fluid into the lungs can cause pneumonia.
To prevent choke, avoid feeding large chunks of food like apples or carrots, grass clippings, and poor-quality hay (overly mature and stemmy). Also, don’t feed after sedation and keep foreign objects out of reach (remove the baler twine!).
Prevention for senior horses or any horse with poor teeth or a previous history of choke includes placing several large rocks in the feeder if the horse bolts his feed and/or soaking the feed. If needed, chose a feed designed to meet the nutritional needs of the horse that can be offered as gruel. Be sure the horse receives proper and regular dental care.
After passing through the esophagus, the feed now enters the stomach through a one-way entry. At the point where the esophagus and stomach join there is a very strong cardiac sphincter valve. This valve prevents food from being regurgitated and does not allow the horse to burp.
The horse’s stomach will usually rupture before this valve allows the material to be regurgitated. A ruptured stomach will result in death. Feed must be of the quality and quantity the horse can handle to avoid stomach distress.
Once through the cardiac sphincter valve the feed arrives in the stomach. The stomach of the horse is very small relative to the size of the horse, holding only about 4 ½ gallons on average. It fills fast and empties fast. The stomach breaks feed down mechanically and chemically.
The equine stomach has four sections:
- Esophageal — basically a storage area
- Cardiac — produces mucous used to coat the stomach and protect it from acidic secretions.
- Fundic — produces enzymes and hydrochloric acid which break down the feed
- Pyloric — produces a small amount of enzymes and mucus
The pyloric section is highly acidic (low pH level). Most of the digestion of feed takes place in the fundic section. The enzyme, pepsin, breaks down protein into amino acids, which can then be utilized by the horse.
The muscles in the stomach use rhythmic contractions called peristalsis. This mechanical action helps break down feed into smaller particles.
The design of the equine stomach is such that a horse needs small frequent meals. It fills quickly and empties quickly. Feed usually only remains in the stomach for about 20 minutes. Ulcers can result if the stomach is allowed to become empty.
Next month we’ll journey into the small intestine.
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The Way of Horses © 2018