Today on Texas Vet News I am going to talk about digestion in horses as it is different than many other domestic animals. Humans, dogs and cats have a simple stomach while cattle have a large rumen in which they can ferment grass and hay. Horses have the best of both worlds in this regard as they have a simple stomach but also have a cecum that acts as a large fermentation vat similar to the rumen in cattle. The difference is that the rumen in cattle is located at the beginning of the digestive tract while the cecum in horses is toward the end of the tract.
What all this means is that horses can eat grass or hay, but they were designed to eat native grass by grazing on thousands of acres. They were not designed to eat large grain meals and large amounts of hay twice a day in a 1-hour period as they are required to do in most situations today. Then they stand around with nothing to eat the other 22 hours of the day and we wonder why we have so many colics, stomach ulcers and founders today.
The small intestine is the major organ of digestion in the horse and this is the areain whichproteins, fats and carbohydrates are digested. Horses were initially thought to have a limited ability to digest fat because they do not have a gall bladder but they are actually efficient at digesting fat because bile from the liver is secreted directly into the small intestine. Non-structural carbohydrates are digested throughout the horse’s GI tract unless the amount of these carbohydrates overwhelms the ability of the small intestine to digest the full amount. The amount that reaches the cecum is rapidly fermented and causes a decrease in pH of the cecum, leading to severe digestive problems and possibly laminitis and founder.