THE EFFECT OF ROUGHAGE SOURCE ON EXERCISE PERFORMANCE AND METABOLISM IN THOROUGHBRED HORSES

The effects of roughage source on metabolism and exercise capacity wer e investigated using 6, previously conditioned, mature thoroughbred ho rses in a cross-over experiment. The horses were assigned to either no n-alfalfa or alfalfa roughage diets which were isocaloric. The diets w ere fed for 2 weeks, after which the horses were exercise tested and t hen fed the alternate diet. Horses were exercised on a high-speed trea dmill using a rapid incremental test. Arterial blood samples were coll ected for blood gas analysis and acid base measurements and venous blo od samples for lactate and red blood cell potassium analysis. Mixed ex pired gas samples were collected for measurement of oxygen uptake, car bon dioxide production and respiratory exchange ratio. Heart rate was measured by telemetry ECG and respiratory frequency by observation. Wh en the 2 diets were compared there were no significant differences in treadmill exercise capacity nor in any of the metabolic or cardiorespi ratory measurements made before, during or after the exercise period. We concluded that roughage source has no effect on cardiorespiratory a nd metabolic function during or after exercise, and does not affect en durance performance during a treadmill exercise test.