Behaviour of Mean Erythrocyte Volume During Submaximal Treadmill Exercise in the Horse

Abstract

The aim of this work was to study the role of spleen contraction in the modification of circulating erythrocyte mean volume during treadmill exercise in the horse. Red blood cells count (RBC), haematocrit (Hct), haemoglobin (Hgb), mean cellular volume (MCV), mean cellular haemoglobin (MCH), mean cellular haemoglobin concentration (MCHC) and red cell distribution width (RDW) were evaluated in five Haflinger mares performing a submaximal incremental test on the treadmill. Blood was collected every minute during the trial without stopping the treadmill. Significant changes of all measured parameters, except for MCH, have been observed. Hct values increased significantly from the 2nd minute from the start of the test. MCV and MCHC values were significantly different from their basal values from the 6th minute of exercise, with MCV being increased and MCHC decreased, suggesting cellular swelling. Hct modifications during brief submaximal exercise have been shown to be mainly and directly related to mobilization of the pool of red blood cells stored in the spleen. However, the evidence in this study of different times of onset of changes between Hct and erythrocyte indices (MCV and MCHC) suggests that exercise-induced alterations in red cell indices are not related to spleen emptying.