Physiological responses of mature Quarter Horses to reining training when fed conventional and fat supplemented diets

Abstract

An initial experiment was conducted utilizing five mature Quarter Horses to establish baseline physiological responses to typical reining training. 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 exercise. The values were used to modify the SET to a degree of difficulty that would elicit anaerobiosis. In a second experiment, ten mature Quarter Horses were exercised by reining horse training in a repeated switchback experiment. Horses were fed a control (C) and a IO% fat-supplemented (F) concentrate with bermudagrass hay in a 65:3 5 ratio. Heart rate (HR), respiration rate (RR), rectal temperature (RT) and venous blood samples were taken prior to, during and following recovery from an SET which simulated reining horse training. Heart rates and plasma lactate concentrations indicated that all maneuvers except loping circles elicited anaerobiosis (208 beats/min and 11.8 mmol/L, respectively). Plasma glucose concentration fell during loping circles from resting concentrations of I 00 mg/dL to 75 mg/dL, increased throughout the remainder of the SET to 90 mg/dL and returned to resting concentrations by 30 min of recovery. Respiration rate, packed cell volume, rectal temperature and non-esterified fatty acids rose throughout the SET and peaked between the end of exercise and after I 0 min of recovery (I 3 0 breaths/min, 5 1%, 3 9.9 'C and .747 mEq/L, respectively). There was no difference in HR between treatments, but HR's were lower (P<.05) on d 28 than on d 0. There were increases (P<.05) in RR on d 28, indicative of more difficult heat dissipation due to increased ambient temperature resulting from environmental changes, but no difference between treatments was observed. A trend was observed for packed cell volume (PCV) to be higher (P<.07) on d 0, but no difference between treatments was observed. Plasma lactate concentrations were higher (P<.05) on d 0, but plasma glucose concentrations and non-esterified fatty acid concentrations did not differ between treatments or d of the SET.