28 Blood Lactate Response of Yearling Horses on a Progressive Workload
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AbstractBlood lactate measurements following exercise provide valuable insight into the metabolic response to different workloads, but minimal research has been published involving yearling horses. Therefore, the objective of the current study was to determine blood lactate response to increasing exercise intensity in yearling horses, hypothesizing that blood lactate levels would peak immediately following exercise, and gradually decrease over a 3 h post-exercise period. To test this, 32 Quarter horses of similar background (480-520 d of age; 16 geldings and 16 fillies) were randomly assigned to one of four groups (n = 8/group) and exercised using an 8-panel free-stall walker. Exercise bouts were 30 min each, divided equally in clockwise and counterclockwise directions. Test 1 consisted of walking at 1.75m/s, and test 2 consisted of horses alternating between the walk and trot at 1.75 and 4.0m/s, respectively. Blood samples were obtained at the onset (PRE) and immediately (H0), half (H0.5), one (H1), and three (H3) h post-exercise. Mean blood lactate was determined using two portable lactate analyzers previously validated for use in horses. Data were analyzed using PROC MIXED in SAS with PRE values used as a covariate. There was a group test time interaction (P > 0.01), where group 3 reached peak lactate concentration at H0 during test 2 (1.37 0.08 mmol/L), while all other groups increased blood lactate concentrations over time to H3 post. Mean lactate post-exercise indicates that horses were able to clear lactate without a sufficient increase in systemic distribution. Values remained below the anaerobic threshold, similar to mature horses, which suggests that sub-maximal exercise in young horses does not elicit an anaerobic response and lactate accumulation.
