PHYSIOLOGICAL-RESPONSES OF MATURE QUARTER HORSES TO REINING TRAINING WHEN FED CONVENTIONAL AND FAT-SUPPLEMENTED DIETS

An initial experiment (Experiment I) was conducted utilizing five matu re Quarter Horses to establish baseline physiological responses to typ ical reining training. In an initial standardized exercise test (SET) which simulated reining horse maneuvers, heart rate and plasma lactate concentration indicated that galloping circles, spinning and stopping were anaerobic maneuvers (203 beats/min and 8.86 mmol/L, respectively ). However, lactate concentrations declined before the end of the SET. The values were used to modify the SET to a degree of difficulty that would elicit significant anaerobiosis, thus maintaining elevated lact ate concentrations throughout the SET. In a subsequent experiment (Exp eriment II), ten mature Quarter Horses were exercised by reining horse training in a crossover experiment. Horses were fed a control (C) and a 10% fat-supplemented (F) concentrate with bermuda grass hay in a 65 :35 ratio. Heart rate (HR), respiration rate (RR), rectal temperature (RT) and venous blood samples were taken prior to, during and followin g recovery from a modified SET which simulated reining horse maneuvers but was more demanding than the previous SET. Heart rates and plasma lactate concentrations indicated that all maneuvers, except loping cir cles elicited anaerobiosis (208 beats/min and 11.8 mmol/L, respectivel y; peak values on d 0). Plasma glucose concentration fell while loping circles from resting concentrations of 104.3 mg/dl to 79.2 mg/dl incr eased throughout the remainder of the SET to 89.7 mg/dl and returned t o resting concentrations by 30 min of recovery. Respiration rate, pack ed cell volume (PCV), rectal temperature and total serum non-esterifie d fatty acid concentration (NEFA) increased throughout the SET and pea ked between the end of exercise and after 10 min of recovery (128 brea ths/min; 51%; 39.9% and .871 mEq/L, respectively). Diet composition ha d no consistent effects on physiological responses, but there were tra ining effects. Heart rate and plasma lactate were lower on day 28 than on day 0 (P<.05) while plasma glucose, NEFA and PCV were not affected by training. Respiration rate and rectal temperature reflected ambien t conditions.