Application of a constant blood withdrawal method in equine exercise physiology studies

The aim of the present study was to test a constant blood withdrawal method (CBWM) to collect blood samples from horses during treadmill exercise. CBW M was performed in 4 Standardbreds and 5 Haflinger horses. A peristaltic pu mp was used to control blood aspiration from an i.v. catheter via an extens ion line. Blood was collected using an automatic fractions collector, with a constant delay time between the drawing of blood and sample collection. B lood withdrawal using CBWM was made during a treadmill standardised exercis e test (SET). A blood flow of 12 ml/min was used and samples collected ever y 60 s during the entire period of exercise. The volume of blood collected in each sample tube was 12.1 +/- 0.2 ml, with a delay time of mean +/- s.d. 25.3 +/- 0.8 s. Plasma lactate kinetics based on measurement of lactate in each fraction showed an exponential increase during the first 13 min of ex ercise (10.5 min of SET and 2.5 min recovery). The peak plasma lactate conc entration was observed between 2.5 and 5.5 min after the end of SET. CBWM p ermits the kinetics of lactate and other blood-borne variables to be studie d over time. This method could be a valuable aid for use in studying equine exercise physiology.