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Keep Concentrate Meals Small for HorsesBy Kentucky Equine Research Staff · December 15, 2016

One tenet of horse feeding that bears repeating over and over relates to concentrates; simply put, keep meal size small. The reasoning rests on the understanding of stomach size and rate of feed passage through the small intestine.

Stomach size. Compared to other mammals of about the same size, horses possess a relatively small stomach. Actual holding capacity of the stomach changes with body size; a Shetland’s stomach is far smaller than a Suffolk Punch’s. An average (think 1,100-lb or 500-kg) horse’s stomach holds about 2 to 4 gallons (9 to 15 liters).

This size serves horses well when they are maintained on an all-forage diet. Times have changed, however, and many horses are fed cereal grains or commercial concentrates to fuel growth and competition goals.

If the capacity of a horse’s stomach is so large, why can’t a horse be given that much feed in one meal?

Good question.

“Depending on the management strategy, the horse’s stomach may already be partially full of forage, such as pasture grass or hay,” remarked Kathleen Crandell, Ph.D., a nutritionist with Kentucky Equine Research (KER).  “After all, full-time access to forage is an advisable way to manage most horses, so long as a suitable forage and an appropriate method of feeding are implemented. An easy keeper, for example, might be fed a mid-quality hay that must be plucked gradually from a slow-feeder.”

The stomach is not fantastically flexible. Though there is some elasticity to the wall, it can be described as a fixed-volume organ. Because horses are incapable of regurgitation, there is only one way for ingesta to travel once it lands in the stomach—toward the small intestine. Overwhelming the stomach with too much feed might cause rupture, which is usually fatal due to widespread contamination of the peritoneal cavity.

Rate of feed passage in the small intestine. The small intestine serves as a major hub for the digestion of many nutrients found in concentrates, including protein and various vitamins and minerals.

Despite its length and capacity, the small intestine is easily overcome with ingesta. Large quantities of concentrates do not dwell in the small intestine long enough to be digested completely. Instead, certain nutrients, including starch, might move on to the large intestine incompletely processed, which can cause hindgut acidosis or laminitis.

So, how much concentrate should be given in one meal?

“The general recommendation is 5 pounds (just over 2 kilograms) or less. A bit more, perhaps an additional pound or half-kilogram, might be acceptable for large horses such as some Warmbloods and draft horses or for horses that predictably take a long time to complete a meal,” said Catherine Whitehouse, M.S., a nutrition advisor KER.

“Feeding recommendations provided by the manufacturer should be followed carefully,” she advised. “Total daily intakes are often more than the 5-pound (2.2-kilogram) suggested meal size, so the daily allotment should be divided into two or three meals.”