The words "nonstructural carbohydrates" have become almost synonymous with "bad news" in the horse industry, mainly because many owners’ goals have been to reduce these sugars and starches (while increasing fat levels) to provide "safer" calories for horses with certain medical conditions. But until recently it was unclear what an NSC diet means for a "normal," nonobese horse.

At the 2011 American Association of Equine Practitioners convention, held Nov. 18-22 in San Antonio, Texas, Joe Pagan, PhD, president of Kentucky Equine Research (KER), described his and colleagues’ research on the effects of carbohydrate and fat intake on glucose tolerance in the healthy horse.

Pagan pointed out that there is a perception among horse owners that feeding any nonstructural carbohydrate to healthy horses will lead to insulin resistance (the inability of the hormone insulin released from the pancreas to manage glucose levels in the bloodstream) and metabolic disorders, even when horses aren’t obese.

Previous studies conducted at KER found that healthy horses fed high-fat diets have a marked delay in clearing glucose, whereas when consuming carbohydrates from sweet feed, glucose returned to normal clearance rates. To test this theory further, his team evaluated four healthy, nonobese Thoroughbred geldings with body condition scores of 5-6 (out of 9), aged around 21.5 years old. The horses were stalled except for six hours of daily turnout with a grazing muzzle