How is feeding carbohydrates related to gastrointestinal (GI) disease? Ray Geor, BVSc, MVSc, PhD, Dipl. ACVIM , professor, Paul Mellon Distinguished Chair, and director of research at Virginia Tech’s Middleburg Agricultural Research and Extension Center in Middleburg, Va. began his discussion of this topic at the 2007 American Association of Equine Practitioners Convention held Dec. 1-5 in Orlando, Fla., by noting the conflict between GI physiology and the way horse owners tend to fed modern horses, especially those with high athletic demands. The propensity to feed high-grain and high-concentrate diets instead of relying on high-fiber diets has increased the incidence of colic. Geor said this is a historic problem, quoting from an 1857 source: “An excess of corn may induce violent indigestion and gripes.”

One study from 1997 indicated that on 31 farms, the risk of colic increased 4 ½ times when horses were fed moderate to large amounts of grain (5-10 pounds).

An increased risk of colic also is related to a change in diet; particularly in the first week after a diet change, there is a chance of simple colonic obstruction or distention, but risk diminishes 15-28 days following dietary changes.

Geor stressed that other contributing factors should be considered, such as a horse’s level of physical activity, breed, age, season, and the area’s weather, but, in general, there is an increased risk of colic with high-grain concentrate diets and with recent dietary changes