How Long Does It Take Food to Digest in a Horse?

Horses were designed by nature to eat a large amount of very low-calorie, hard-to-digest food: grass. But modern hay and grain-based feeds are far easier for a horse to digest and subsequently go through a horse's digestive system faster. A horse that can't get access to much water will have a slower digestion than a horse that can drink his fill.

The first part of the horse's digestive process is chewing the food. Feral horses spend an average of 15 hours a day grazing. Modern racehorses eat their grain in less than 1 hour and have access to a hay bag for a few more hours and sometimes overnight. Grazing mixes ground food with saliva, which begins the process of breaking food down into energy the body can use.

The average horse's stomach can hold about 2 gallons (or 8 to 15 liters). Feed moves quickly through the stomach, where fats are digested by enzymes. The stomach empties in less than 15 minutes; food goes into the small intestine and then the cecum, which is between the small and large intestines (further divided into the large and small colon). The real job of digestion begins in the cecum (similar to a cow's rumen), where there are friendly cellulose-eating bacteria that break down plant material into nutrients.

Digestion is a slow job in a horse's intestines, because grass is such a difficult food to digest. So a horse's intestines are an average of 70 feet long. The food moves through the intestines at an average rate of 1 foot per minute. Grass and loose hay take slightly longer to travel than grain or pelleted hay.

The undigestible material of the food enters the rectum in the form of feces and is then excreted out of the anus. On average, a horse excretes about 38.5 pounds (17.5 kilograms) of feces per day. If a horse has not excreted any feces within 6 hours of eating, it can be assumed that the horse may be colicking. Call a vet immediately.

On average, a stomach full of food will go through a horse in about 1 hour. This may be quicker for horses eating grain or one that has had some intestines removed due to colic surgery. Horses should not be worked when they are digesting rich feed, or it may make them colicky. Always wait 1 hour after feeding before riding or working your horse or pony.