Slowing Feed Intake Reduces Glycemic Response in HorsesBy Kentucky Equine Research Staff · August 27, 2013
When horses consume large grain meals, glucose floods into the bloodstream (glycemic response), triggering a reaction in which the body produces insulin to deal with the sugar overload (insulinemic response). These reactions are foreign to the natural digestive pattern in which a horse grazes continuously on medium-quality forage, rarely if ever ingesting carbohydrate-rich grains. This unnatural feeding pattern can cause health problems in some equines. Young growing horses are more likely to develop skeletal problems if they are fed grain products that produce large glycemic responses. In mature horses, gobbling a large grain meal may lead to obesity, insulin resistance, colic, laminitis, or metabolic syndrome.
Owners can avoid some problems by choosing feeds or grains that produce a low glycemic response and feeding grain only when the horse needs the extra calories to meet the requirements of work, growth, or reproduction. Other ways to slow glycemic and insulinemic responses are to replace large grain meals with smaller, more frequent feedings. Slowing the rate at which a horse ingests grain or hay can also help to avoid spikes in blood glucose.
To measure the effect of slowing feed intake rate, a research team at North Carolina State University's Department of Animal Science set up two experiments. In the first trial, eight healthy mature horses were randomly assigned to one of four treatments. Every horse was given a single concentrate meal consisting of 2 g/kg of body weight of a 26% nonstructural carbohydrate (NSC) pelleted feed. Feed was provided by control (an unaltered rubber bucket); “ball” (a bucket with four movable bocce-style balls placed in it); “waffle” (a bucket containing stationary obstacles below the feed); or “water” (an unaltered bucket with concentrate soaked in an equal portion of water for 20 minutes).
The researchers measured the time each horse required to eat the grain, and also collected jugular blood samples after the meals. Results showed that both the ball and waffle treatments increased the time it took the horses to finish their meals by almost 50% compared to control and water treatments. Horses in the ball treatment group had the lowest glucose and insulin responses of the four treatments.
In a second trial, the team looked at the effect on four healthy mature geldings when the same four feeding methods were used over a four-day period. Times to consume feed varied through the period, but it was still clear that using feeders with obstacles was effective in slowing the rate of consumption. It is recommended that horse owners should consider using some sort of slow feeder for both hay and grain to more nearly match the natural eating pattern of their horses and avoid spikes in glycemic response.