Hematological and Biochemical Changes in Mangalarga Marchador Horses After a Four-Beat Gait Challenge in Three Different Distances

The “marcha” is a comfortable equestrian four-beat gait characterized as a submaximal exercise. Four healthy Mangalarga Marchador horses of 6-7 years of age were assessed under field conditions covering distances of 12.7, 19.3, and 38.8 km. Blood samples were collected before, during, and at the end of the exercise, as well as after 4 hours of rest, to measure the hematological, biochemical, and enzymatic biomarkers' variations. The following measurements were recorded: red blood cells (RBCs); hematocrit (HT); hemoglobin (HB); red cell dispersion width (RDW); white blood cells (WBCs); absolute lymphocytes count (LYM); relative lymphocytes count (LYMr); total plasmatic protein (PPT); creatine kinase (CK); uric acid (UA); dehydrogenase lactic (LDH); and aspartate aminotransferase (AST). Significant alterations related to the different distances covered were observed for lymphocytes (LYM and LYMr), which were lower (P < .05) when horses were exercised for 38.8 km. The physical exercise caused significant alterations (P < .05) in all biomarkers investigated, except for AST. During the four-beat gait challenges, the RBCs, HT, HB, RDW, WBCs, and PPT rose and remained high after the 4-hour rest. At the same time, the UA, LDH, and CK were greater during the exercise but returned to basal values after the 4-hour rest. The four-beat gait challenges promoted significant variations on the hematological and biochemical markers in Mangalarga Marchador horses, as well as a decrease in the horses' lymphocyte number after 38.8 km of exercise.