Digestive System of the Horse
Compared to the rest of your horse's digestive tract, the stomach is quite small. Her stomach can't handle a lot of food at once, but if she doesn't eat enough, gas can build up and cause colic.
The Foregut
When your horse eats, her teeth grind and pulverize the feed. It travels down to her stomach, where it is mixed, stored and partially digested before being passed to the small intestine or upper gut where most nutrients are absorbed. Food passes through the stomach and small intestine quickly. If your horse eats too much too quickly, large amounts of soluble carbohydrates may pass to the large intestine and ferment, causing...you guessed it...colic.
The Hindgut
When the optimum amount of food passes through the small intestine, it enters the cecum (which forms, with the large colon, the organ known as the large intestine or hindgut). The cecum ferments undigested nutrients and passes the results on to the colon for further digestion. Fermentation produces nutrients vital to your horse's health but fermentation can also produce a gas colic. If large amounts of soluble carbs such as starch reach the hindgut, gases may be produced faster than your horse can absorb or release them.
Your horse's digestive tract is designed for continuous grazing. Learn the best feeding techniques to prevent or minimize colic episodes.
Image courtesy of D.D. Householder and G.D. Potter, Texas A&M University