Metabolic Response to Exercise in Arabian and Thoroughbred Horses

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By Kentucky Equine Research Staff · May 11, 2011

Many people tend to think of Thoroughbreds as racehorses that excel at high-intensity exercise, and of Arabians as endurance horses whose strengths lie with low-intensity exercise. Are these perceptions based simply on the most common use of each breed, or on particular innate characteristics or abilities that set the breeds apart? A study conducted at Kentucky Equine Research was designed to test the hypothesis that Thoroughbreds are better suited to high-intensity exercise because they have greater aerobic and anaerobic capacities than Arabians.

Arabians have a higher proportion of oxidative muscle fibers (types I and IIa) than Thoroughbreds. For that reason, it was hypothesized that Arabians would make greater use of fat for energy. The study tested this hypothesis as well.

The study compared selected measures of exercise capacity and metabolism in a small group of Thoroughbreds and Arabians of similar age, training background, and diet. Five Thoroughbred and five Arabian geldings were placed on identical exercise programs and fed identical diets for two months. Each horse then performed three exercise trials on a high-speed treadmill set at a 3-degree incline.

Trial 1 was an incremental test in which each horse ran at a steadily increasing pace until he could no longer maintain speed. This trial determined each horse’s aerobic capacity...

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