Changes in Blood Parameters in Healthy Horses and Horses With Upper and Lower Respiratory Tract Diseases Undergoing Treadmill Exercise Tests

Exercise tests are useful tools to evaluate the fitness level of horses in training or with a history of poor performance. The aim of this study was to evaluate the differences in blood parameters in three groups of horses undergoing treadmill exercise tests, either to detect the cause of exercise intolerance or to evaluate the level of fitness before a competition. Blood samples were taken from 30 horses before, at the end of, and two hours after a standardized treadmill exercise test, to detect differences in hematological parameters between healthy horses (10, group N), horses with upper (10, group U), and lower airway diseases (10, group L). Packed cell volume, erythrocyte number, hemoglobin, glucose, and total and unconjugated bilirubin concentration were statistically different between the groups, because of increased oxygen demands in respiratory diseases and intravascular hemolysis. This could occur during exercise and is worsened by the increased breakdown of erythrocytes secondary to exercise-induced pulmonary hemorrhage, diagnosed in horses in group L.