PHYSIOLOGICAL-RESPONSES TO TRAINING AND RACING IN 2-YEAR-OLD QUARTER HORSES

Beginning at approximately 18 mo of age, fifty-three Quarter Horses we re trained to ride, conditioned and run in nine match races with three each at 274 m, 320 m and 366 m. As part of a companion study, the hor ses were fed varying amounts of Sodium Zeolite A. During the last long slow distance (LSD) workout, the last LSD with sprints workout prior to racing, and each race, blood samples were collected and heart rates (HR), respiration rates (RR) and rectal temperatures (RT) were measur ed at rest, after the warm-up, and at 1, 2, 5, 10, 20, 30, 60 and 120 min of recovery. Blood samples were analyzed for packed cell volume (P CV) and plasma ionized calcium (Ca++), sodium (Na+), potassium (K+), l actate (LA-) and glucose (GLU) concentrations. Data were analyzed by A NOVA using the general linear model of SAS appropriate for repeated me asures and Scheffe's multiple comparison test to compare diet, race an d sample (time) effects. Results were considered significant at P < .1 . In this study, there were no physiologically important diet related differences, therefore training and racing effects were reported over the entire group of horses. The horses were able to run increasingly l onger races without corresponding changes in HR, PCV or plasma Na+, K, Ca++, LA- or GLU concentrations. The warm-up elicited an average HR of 163 beats/min, yet HR during and immediately after the races did no t go as high as commonly observed in Thoroughbred racehorses running l onger distances. Respiration rate and RT were higher during recovery f rom the longer races in response to increased metabolically generated heat.