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Feeding Horses: Effects of Meals on the Equine Gastrointestinal Tract
|Created:||December 9, 2015|
Let’s not mince words: horses and ponies are healthiest and happiest when they’re allowed the freedom to consume forage whenever they choose. The gastrointestinal tract is laid out
Feeding Horses: Effects of Meals on the Equine Gastrointestinal TractBy Kentucky Equine Research Staff · November 13, 2015
Let’s not mince words: horses and ponies are healthiest and happiest when they’re allowed the freedom to consume forage whenever they choose. The gastrointestinal tract is laid out to accommodate near-constant processing of fibrous feedstuffs. Horses run into problems, however, when they are fed meals—one, two, or three large feedings a day with nothing in between. Meal feeding can be problematic for key compartments of the gastrointestinal tract, principally the stomach and hindgut.
To maintain stomach and hindgut health, forage should be fed as often as possible.
Stomach. With a volume of approximately 2-4 gallons (7.5-15 liters), the stomach of a 1,100-lb (500-kg) horse is not as capacious as one might think, especially considering the physical size of the horse or the total capacity of the gastrointestinal tract, which is about 37-50 gallons (140-174 liters). “Because of the horse’s natural grazing behavior, there is little need for the stomach to be voluminous, as ingesta passes fairly quickly from the stomach,” said Kathleen Crandell, Ph.D., a nutritionist with Kentucky Equine Research (KER).
In fact, about 75% of ingesta passes through the stomach within 30 minutes of consumption. As a horse chews, saliva is produced. Coupled with the in-and-out flow of ingesta, the natural buffering capacity of saliva keeps ulcers from forming in the stomach, according to Crandell.
Now, consider a horse with no access to forage.
“With nothing to chew, the horse produces little to no saliva. Soon after the last meal the stomach is devoid of ingesta, as it has moved along to the small intestine for further processing,” explained Crandell. “Sitting empty, the stomach begins to accumulate gastric acid. Without any buffers to neutralize the acid, the stomach lining becomes compromised and ulcers may develop.”
The effects of meal feeding on the stomach materialize swiftly. Researchers have found that ulcer formation can happen in a matter of days, not months or years.
Hindgut. The cecum, large colon, and small colon are often grouped and thought of as one entity, the hindgut. The cecum is home to billions of microorganisms that digest fiber. Through the efforts of these microorganisms, a great deal of energy is produced for growth, work, and maintenance of body systems.
“The hindgut functions best when given the opportunity to regularly process fiber-rich feedstuffs like pasture, hay, haylage, and hay cubes. These feedstuffs keep the microorganisms robust and well-fed, and the balance of different microbial species in the hindgut remains optimal,” said Crandell.
When horses are fed large grain meals and minimal forage, the hindgut suffers.
“Because the small intestine becomes overwhelmed when large grain meals are fed, ingesta passes to the cecum incompletely digested. Unfortunately, this starch-rich ingesta is detrimental to the cecum, often causing monumental shifts in the microbial population and affecting the pH of the entire hindgut,” explained Crandell. Fluctuating pH levels in the hindgut can cause recurrent, low-level colic, behavioral issues, and certain vices such as wood-chewing and stall-walking.
To maintain stomach and hindgut health, forage should be fed as often as possible. The appropriate forage for an individual horse must be found; horses with high-energy needs might do best on abundant pasture and a legume forage, whereas an easy keeper could likely derive sufficient energy from mid-quality pasture or hay. Slowing forage intake is frequently necessary for some easy keepers, and this can be achieved through grazing muzzles and slow-feed devices such as haynets with small openings.