As most horse owners know, hay plays an important role in keeping a horse’s digestive system healthy and functioning well. Kathleen Crandell, Ph.D., an equine nutritionist for Kentucky Equine Research (KER), said this is due in part to the fiber content provided by hay, which assists the specific design of a horse’s body.
Once a free-grazing animal, horses have evolved to live predominately in confined areas and receive fewer, heavier feedings. This can cause complications for a digestive tract designed to process food quickly and with optimal energy utilization.
“The overall size of the horse’s stomach is relatively small compared to the rest of the digestive tract,” Crandell said. “That’s because these animals evolved eating small amounts of food for long periods of time, grazing between 14 and 20 hours in a day.”
Crandell explained that most digestion of proteins, starches, fats, vitamins and minerals occurs in the section of the horse’s gastrointestinal tract known as the foregut. What is not digested in the foregut, along with most of the fiber, spills over into the hindgut, which relies heavily on microbes for digestion.
“In the human diet, we don’t digest fiber well; we don’t have the right microbes,” Crandell said. “But a horse does. And most of those – the bacteria and protozoa and yeast – live throughout the digestive tract in smaller numbers, but they are super concentrated in the cecum and colon [hindgut] of the horse.
“Keeping that microbial population balanced and happy is really important,” Crandell added. “That can be done by [the horse] getting a steady diet of high-quality forage and not making changes rapidly.”