Selected electrolytic, haematological and enzymatic parameters in horses during endurance races

Long-distance endurance races are a big challenge for a horse’s body. The prolonged exercise and dehydration associated with it, in adverse circumstances, may dysregulate many metabolic processes. The aim of this study was to assess changes in electrolyte balance in horses during endurance races, and to explain the potential need for electrolyte supplementation. The experiment was performed on fifty-six horses aged 9-15 years. Haematological and biochemical parameters of horse blood were tested before, during and after the completion of a 120 km endurance race. Electrolyte status (Na+, K+, Cl-) was assessed by analysing test results in horses that completed the race without any clinical symptoms of metabolic disorders and received no additional mineral supplements before the race. The following haematological parameters were determined: red blood cell and white blood cell counts, haemoglobin levels, haematocrit and red blood cell indices (MCV, MCH, MCHC). Enzymatic tests involved the serum levels of lactate dehydrogenase and creatine kinase. A significant increase was found in the levels of haemoglobin, lactate dehydrogenase and creatine kinase activity, but the values of these parameters were within the normal physiological ranges. Other parameters (WBC, RBC, Ht, MCV, MCH, MCHC, Na+, K+, Cl-) changed slightly, but were also within the ranges characteristic of sporthorses. The results suggest that horses well prepared for effort do not require additional supplementation of minerals during endurance races under conditions of the Polish climate.