Effect of exercise on glucocorticoids and other cellular components of blood

The effect of exercise during the dry period on glucocorticoids, packed cell volume, hemoglobin concentration, total leucocytes, and differential leucocyte count was examined with 87 Holstein cows. Cows were divided randomly into groups: 1) control, 2) 3.2 km at 3.5 km/h, 3) 9.6 km at 3.5 km/h, and 4) 3.2 km at 5.5 km/h. Sampling for blood analysis was at weekly intervals preexercise and immediately postexercise. Both glucocorticoids and hemoglobin concentrations were increased by exercise. Correlations between glucocorticoids and most other traits were practically zero. No eosinopenia was noted with increasing glucocorticoids. Lymphocyte numbers were correlated negatively with all traits measured. Glucocorticoid concentration increased from pre- to postexercise with both distance and speed. Although glucocorticoid concentration varied among cows, neither day sampled, days dry, weight, nor age affected glucocorticoids. Increased hemoglobin of postexercise cows could not be attributed to speed or distance exercised. Traits measured in this study, other than glucocorticoid concentration, are ineffective in evaluating response to increased exercise.