Follow That Bite
Fascinating Facts about the Horse’s Digestive Tract
Think you know everything about the inside of a horse? Test your knowledge, and maybe learn some surprising facts, by taking this short quiz as you follow an imaginary bite of grass through the digestive tract.
1. True or false: Horses can normally eat all day long without getting a bellyache.
TRUE. In fact, most horses are less likely to colic if allowed access to grass or hay whenever they choose. The horse’s digestive tract is designed to process a continuous flow of food. It’s not unusual to see horses foraging for hours at a time, especially if food is sparse. Given access to pastureland that contains plenty to eat, horses might spend much of their time participating in other activities such as grooming their pasturemates, dozing under a favourite tree, or lying about in peaceful slumber. The decision to eat depends largely on how hungry a horse is! Scientists have measured the amount of time horses graze in free-roaming situations. Though estimates vary, horses are thought to graze 50-75% of the time.
2. True or false: Horses have teeth that are five, six, or even seven inches long.
TRUE. Horses shed their deciduous or 'baby' teeth completely by the time they are about six years old. The teeth are replaced by a collection of permanent teeth (typically 36 in mares, 40 in geldings and stallions). Both the incisors, the teeth in the front of the horse’s mouth, and the molars, the square grinders in the back of the jaw, are much longer than they appear, as only a portion of each tooth is visible outside the gum line. The total length of a horse’s incisor is about five and a quarter inches, while the longest molar might be closer to seven inches. A horse’s teeth continue to erupt throughout its lifetime at a rate of approximately one-third of an inch annually. Given six inches of crown, the cheek teeth would serve a horse about 18 years, give or take a few years.
3. True or false: Horses produce buckets of saliva every day.
TRUE. Scientists estimate that a normal horse will produce about 10 gallons of saliva daily. Certain factors affect saliva production, the most notable of which is diet. A diet high in dry forage such as hay causes horses to salivate more than a diet high in moisture (green grass). Horses use saliva to help them chew and swallow food, just as humans do. In the horse, however, saliva is critical to the health of the stomach. Constant introduction of saliva into the stomach neutralizes gastric acid, reducing the likelihood of ulceration.
4. True or false: Horses can vomit.
FALSE. Most horses cannot vomit. The strong muscles responsible for contracting and relaxing a one-way valve at the base of the horse's oesophagus usually prevent regurgitation. Despite this inability to vomit, rupture of the stomach is rare because the stomach typically begins to empty before it fills to capacity. If vomiting does occur, it is usually a sign that the stomach might have ruptured or that rupture is imminent, almost always a fatal development.
5. True or false: Horses get heartburn.
FALSE. Though many humans suffer from heartburn (pain or burning associated with regurgitation of gastric fluid into the oesophagus), horses do not. As mentioned earlier, it’s nearly impossible for chewed food, gastric acid, or a combination of both to backtrack into the oesophagus. Horses do, however, develop gastric ulcers, raw areas in the stomach lining that cause pain, discomfort, reduced appetite, and a sour disposition.
6. True or false: Horses can get hiccups.
TRUE. In humans, a hiccup is a diaphragmatic spasm that causes sudden inhalation, which in turn produces the characteristic sound. Though they are not hiccups per se, horses sometimes suffer from 'thumps', a similar irregularity in diaphragm function. The scientific name for thumps is synchronous diaphragmatic flutter, a condition characterized by involuntary contractions of the diaphragm that are simultaneous with the horse’s heartbeat. An observer can see the hiccup-like movement in the horse’s side, and can sometimes hear a thumping noise with each contraction, thus the common name. Thumps is most often brought on by a loss of electrolytes during or following physical exertion. It is not a disorder of the gastrointestinal tract, but one of the horse’s respiratory mechanism.
7. True or false: Horses don’t have gall bladders.
TRUE. In humans, the gall bladder serves as a reservoir for bile, a fluid produced by the liver to aid in the digestion of fats. In the horse, bile is dumped directly into the duodenum, the segment of small intestine that connects to the stomach. It is in the folds of the duodenum that bile emulsifies fats (turning large fat globules into smaller particles) and aids in the movement of ingested food through the remainder of the small intestine.
8. True or false: The horse has a bacteria-filled organ called the blind gut.
TRUE. The horse does have an abdominal organ with the nickname of 'blind gut'. The proper name for the blind gut is the caecum. This part of the large intestine is populated by billions of bacteria, protozoa, and fungi that aid in the digestion of fiber and carbohydrates. The microbes’ specific contribution is fermentation, or the anaerobic breakdown of feedstuffs for energy. Without these microorganisms, horses would derive little benefit from forages such as grass and hay.
9. True or false: The intestines of the horse can stretch the length of a football field.
FALSE. The normal horse’s small intestine is about 70 feet long, and his hindgut (caecum, small colon, large colon, and rectum) is approximately 26 feet, which totals nearly 100 feet. When stretched from end to end, the horse’s intestinal tract is much shorter than the length of a football field (300 feet).
By Kentucky Equine Research - Last updated 16 November 2012
