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Understanding Your Horse's Digestive System

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horse tooth

A milk or deciduous tooth from a young horse.

2007 K. Blocksdorf
For all that a horse suggests strength, speed and stamina, their digestive systems are remarkably delicate. In terms of their diets, they are herbivore specialists who can only process one type of plant material efficiently. Too much, too little, or the wrong kind of foods can all cause digestive upsets that can lead to illness or fatality.

Your Horse's Teeth

As with all animals, digestion starts in the mouth. Horses have evolved to efficiently crop grass with their fore teeth and grind it with the back teeth. A horse will have two sets of teeth. At about two to three years of age, a young horse will lose its milk teeth. The adult teeth that grow in continue to grow throughout most of its life. There are specific patterns of tooth growth that make it possible to estimate how old a horse is.

Because horses can spend up to 95% grazing close to the ground, a fair amount of grit is ingested. This grit continually grinds down the horse’s teeth. In domestic horses, tooth wear can be uneven or growth can exceed the amount of wear. This makes a yearly visit from an equine dentist a necessity to remove any excess growth or sharp edges that could form.

Swallowing

Horses hold their food at the back of the mouth before swallowing. Thoroughly mixed with saliva it is propelled down the esophagus by strong muscular contractions. Ideally, there is enough saliva to help the food down, but a greedy eater who doesn’t chew its food completely and hasn’t enough saliva mixed with the ground-up food can choke.

The food then travels to the horse’s stomach. Unlike cattle which are ruminants with several stomachs, horses have only one stomach. Horse’s small stomachs function best if it is never quite full. A full stomach may feel satisfying to humans, but it can be very uncomfortable, and even harmful for a horse. Because the valve into the stomach only opens only one way, horses can not regurgitate. If something is eaten to disrupt the digestives system there is only one direction it can go.

In the Stomach

In the stomach the food is mixed with more acids and enzymes that help break it down. Food then travels into the small intestine where more secretions from the intestine and organs such as the liver and pancreas break it down into basic components; the nutrients and energy that the horse requires.

The Large Intestine

Once the food has traveled through the small intestine it enters the large intestine. This is where most of the water is extracted from the food, and the fiber is broken down. Put an ear, or stethoscope to the side of the horse’s belly and you should hear the rumble and gurgle of a healthy functioning gut. The large intestine is also the location of the caecum, a section of the intestine that can be filled with the ingested grit causing sand colic. Because of the narrow bends within the intestinal system, impacted food can cause constipation and colic. Twisting or telescoping of the gut can occur, causing extreme pain. Unfortunately, even with today’s excellent veterinary care many horses that twist a gut may be euthanized.

From the large intestine feces travels to the rectum and is expelled through the anus, most often into a freshly cleaned stall. The whole process of digestion can take up to 48 hours.

Your Horse's Furnace

Two other by-products of the process are heat and gas. Usually gas passes harmlessly. The heat generated by the digestive process is important for keeping the horse warm during frigid temperatures. The best way to keep a horse warm is to give it free access to hay.

Digestive Upsets

Horses can suffer digestive distress from toxic plants, stress, bacteria such as salmonella, parasites, overeating, and swallowing foreign objects. All of these factors can result in colic. Colic is an indication of abdominal pain, and is not a condition in itself. Colic symptoms include: kicking or biting at the sides, elevated pulse, violent rolling on the ground, dull, listless or unusually irritated behavior, constipation, decreased gut sounds, sweating, and refusal to eat or drink. If your horse is exhibiting colic symptoms call your veterinarian immediately.

Maintaining a Healthy Gut

Keep your horse’s digestive system healthy by providing plenty of clean water, good-quality hay or pasture and plenty of exercise. A regular de-worming program will help eliminate parasite damaging infestations and regular dental care will ensure that your horse is grinding his food efficiently.
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