Although horse people have studied and are aware of the horse digestive tract, it never hurts to take a few minutes to refresh the knowledge. There is always something new to learn about that special friend waiting for you out in the barn. ~ Jerry
By: By Bradford G. Bentz, VMD, MS, Dipl. ACVIM, ABVP (equine)
The horse’s evolution as a forage eater helps in understanding its digestive system, which is designed for continuous grazing of grass forages. The stomach and the small intestine can receive a nearly continuous flow of small amounts of food.
The large intestine has been adapted to extract extra nutrition from the fiber content of the forages that pass through the small intestine.
Domestication of the horse is at odds with an intestinal system well developed for continual grazing. Convenience to owners, modern equine athletic activities, and space limitations dictate modern feeding practices and force horses to receive more concentrated feeds at infrequent intervals, harvested and processed forages, and reduced access to pasture that permits natural grazing.
Cereal grains and fats have, therefore, been artificially increased in the diets of domesticated horses. Because the intestinal tract is not “designed” for this type of feeding, we see more digestive disturbances in horses receiving these modern management and feeding practices.
Although the anatomy of the equine intestinal tract is not dissimilar from that of other mammals, its organization and physiologic function differ. From the mouth to the beginning of the large intestine at the segment called the cecum, the digestive tract functions similarly to that of humans.
However, the horse has a comparatively reduced capacity for digestion. Salivary digestion of carbohydrates occurs in humans and other species, but such digestion is minimal in horses.
Beyond the cecum, the large intestine functions more like that of the forestomachs of a ruminant such as a cow. In the cecum and large intestine there is continual fermentation of dietary fiber. Normal function of the hindgut (intestinal tract beyond the small intestine) of the horse is highly dependent on an adequate source of dietary fiber, and without it the horse is at risk of developing various dietary imbalances.
As in humans, a horse’s digestion process begins in the mouth, where grasping of food and manipulation and chewing by the lips, tongue, and teeth allow grinding of feed into smaller pieces. This is particularly important for efficient digestion of fibrous feeds such as hay and for grinding and digestion of whole grains.