Understanding Your Horse’s Digestive System

Unlike us, horses have very complicated digestive systems. Known as “hindgut fermenters,” horses’ intestines take weird twists and turns with some unexpected surprises, all to grass and hay. Let’s take a tour of the horse’s digestive tract from mouth to tail.

Biting and Chewing

If you were a blade of grass, your fate would be sealed starting at the horse’s mouth. The horse’s incisors, or front teeth, easily snip grass into bite-sized pieces. Then the tongue, made of strong muscle, moves the grass to the back of the mouth, where it is ground down by large molars with ridged surfaces.

Watch your horse chew and notice the side-to-side motion of his jaw. This movement is perfect for grinding tough fiber into smaller pieces. Sometimes horses develop sharp points on their molars that result in uneven chewing and mouth sores that are very painful. Regular dental filing, called floating, done by your veterinarian will help prevent this from happening.

To the Stomach

Next, the grass is swallowed and travels down the esophagus, a muscular tube connecting the throat to the stomach. Occasionally, dry feed will get stuck here. This is called choke, which is a little confusing, because it has nothing to do with the horse’s breathing ability.

The horse’s front teeth, called incisors, are perfectly shaped to snip grass. The tongue moves food to the back of the mouth for grinding in the molars. Photo by Wanderlust Media/Shutterstock

If a horse has a case of choke, he can’t swallow, may drool, and will sometimes play in water but not drink. This is an emergency situation, so your veterinarian should be called right away to treat it.

Once down the esophagus, grass enters the stomach, a surprisingly small organ in the horse. Part of the stomach has special glands that secrete strong acid, which breaks down food. It is common for this acid to cause gastric ulcers in some horses due to stress, inappropriate feeding, and other issues. A veterinarian can diagnose gastric ulcers and then prescribe treatment and dietary changes for your horse if needed.

The stomach is also where bot fly larvae develop. Adult bot flies lay eggs on your horse’s legs. When he scratches, he accidentally swallows them, and they attach to the lining of the stomach and develop into larvae. Many common deworming medications prevent this type of infestation.

Small Intestine

Food doesn’t stay in the horse’s stomach for long. It moves quickly through the small intestine, an impressively long tube that can reach up to 70 feet in an adult horse! The small intestine is where digestion of protein and fat occurs, along with some carbohydrates.

Your horse needs the help of healthy bacteria and protozoa to do most of the digestion of grass and hay via chemical reactions called fermentation. This occurs beyond the small intestine in what is called the “hindgut.”