The effect of soybean oil inclusion in the diet of four mature Quarter horse cross geldings, having approximately 42 months of age and averaging 382kg was evaluated. The horses were submitted to a moderate intensity exercise, and received the control diet (without soybean oil) and the diet containing soybean oil (4.7%) twice a day for three periods of 21 days in a Switch-back design. The amount of ration was offered in a way to achieve a daily isoproteic and isoenergetic intake for both treatments. The following parameters were evaluated: heart rate (HR), respiratory rate (RR) and muscle glycogen concentration, before and 20 minutes after the end of the exercise, and glucose and lactate plasma levels before the exercise and at 10, 20, 30 and 50 minutes after the exercise. The increase of oil level in the diet did not affect significantly (P>0.05) the HR, the RR, the glucose and lactate plasma levels, before and after the exercise. The muscle glycogen concentration was higher (P<0.025), before exercise, for the horses that received the diet containing soybean oil. The increase of glycogen concentration in horses conditioned to consume a diet containing soybean oil may imply in a greater amount of energy to the muscle activity during exercising.
equine; glycogen; glucose; lactate; oil
