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Feeding Horses Before Exercise: What to Feed and When?By Kentucky Equine Research Staff · September 25, 2017

Three experiments were conducted to evaluate if feeding hay with and without grain affects glycemic response and hematological responses in Thoroughbred horses at rest and during a simulated competition exercise test on a high-speed treadmill. The first experiment evaluated how feeding forage along with grain influences plasma variables and water intake. The second experiment was conducted to determine whether these changes affect exercise performance. The third experiment was conducted to determine how forage alone affects exercise response.

Results showed that time of hay feeding affects glycemic response, plasma protein, and water intake post grain feeding. Free-choice hay feeding resulted in a 9% reduction in plasma volume. Fasted horses had lower blood lactate after exercise compared to the grain fed treatments. Heart rate was significantly different between treatments. Feeding only forage before exercise had a much smaller effect on glycemic and insulin response to exercise than a grain meal. Forage did not affect free fatty acid availability.

This study showed that grain should not be fed before exercise. Small amounts of hay or grazing do not adversely affect performance and will stimulate saliva production which may help preserve gastrointestinal integrity.

This report of KER's 1994 research was published in Advances in Equine Nutrition II.

Read the entire research paper, titled Timing and Amount of Forage and Grain Affects Exercise Response in Thoroughbred Horses.