EFFECT OF FEEDING STATE ON THE RESPONSE OF HORSES TO REPEATED BOUTS OF INTENSE EXERCISE

Four mature Standardbred horses were used in a 2-period cross-over des ign experiment to evaluate the effect of feeding state (fed or fasted) on metabolic response to 2 repeated bouts of exercise. Horses were ei ther fasted 15 to 16 h before exercise or fasted for 12 h and then fed 2 kg of whole corn 2.5 to 3 h before exercise. In the first period, 2 horses in each feeding state were exercised. In the second period, th e treatments were switched. The exercise test consisted of 2 exercise bouts separated by a 90 min recovery period. Each exercise bout includ ed a warm-up phase and a high intensity phase (1600 m at 11 mis on a 2 % graded treadmill). Blood samples collected during the exercise test were analysed for glucose, non-esterified fatty acids (NEFA), insulin and lactate concentrations. Fasted horses had lower insulin concentrat ions and higher NEFA concentrations at the onset of exercise (P<0.05). NEFA concentrations were consistently higher (P<0.05) in the fasted h orses until the high intensity phase of the second exercise bout. Feed ing state did not affect heart rate or plasma lactate responses to exe rcise. Plasma glucose concentrations tended to decline in the fed hors es during the first exercise bout. Neither a positive nor a negative e ffect of feeding state on horses performing repeated bouts of intense exercise were found.