Effect of age and of performance parameters on CK, LDH and AST activities in plasma of standardbred horses during exercise

Abstract

The objective of the study was to examine whether age, racing time record, V4 or V200 of standardbred horses had an effect on the changes of CK, LDH and AST activities in plasma during exercise (V4 and V200 = velocities run under the defined conditions inducing 4 mmol/l blood lactate concentration and 200 beats/min). For this purpose 15 standardbred horses were submitted to a standardized exercise test (SET). The SET consisted of four or more runs depending on when the blood lactate concentration of a horse exceeded 4 mmol/l. Speed in the first run was 6 m/s, and it was increased by 1 m/s for each run. The blood lactate concentration measured after each run and the mean heart rate during each run was plotted against running speed to derive V4 and V200 from the blood lactate- and heart rate-running speed relation. The median values of the enzyme activities in plasma of two-year old horses increased significantly during the exercise test. The median LDH and AST activities in plasma of the horses older than two years increased significantly too, but at later runs than in plasma of two-year old horses. The median CK activity in plasma of horses older than two years did not change during the test. The comparison of the median enzyme activities in plasma of horses at different sampling times demonstrated that the difference in age only showed up in the CK activity after the 4th run. There was no significant relationship between the racing time record, V4 or V200 and the absolute or relative difference of the change of the activities of the enzymes measured.