The horse evolved as a grazing animal that escaped predators by flight and adapted to an almost constant supply of forage, which was predominantly digested in the hindgut. Today the horse is expected to carry a rider and undertake fairly exhaustive repetitive work. The horse therefore often needs more energy than it would have required in the wild.
Consider a 500-kg (1,100-lb) three-day event horse. If this horse were to be fed only hay to meet its energy requirement for high-intensity competition as well as sustaining life, it would need to eat around 22 kg (slightly less than 50 pounds) of hay, an impossible amount to consume. If oats were substituted as part of the diet, then the ration would become more realistic. With the addition of energy-dense fat, the diet could most easily match energy requirement with manageable intake.
Feeding fat reduces the amount of concentrates necessary to meet energy requirements, which effectively means a horse can retain a healthy fiber intake despite a high energy needs. Kathleen Crandell, PhD, an equine nutritionist with Kentucky Equine Research, explains, “Fat increases the energy density of a feed so that a horse can consume more energy even if appetite decreases. Because of a more efficient conversion to mechanical energy than fiber or carbohydrate, dietary fat also decrease the horse’s heat load, a useful factor during performance in hot and humid conditions.”
Long-term fat supplementation, in combination with appropriate training, has been suggested to result in several adaptations that could result in improved performance. These include increased mobilization of free fatty acids (FFA), increased speed of uptake of FFA into muscle, and a glycogen-sparing effect so that fatigue is delayed and performance improved. In addition, added dietary fat may increase high-intensity exercise capacity and pre-exercise muscle glycogen levels.
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