Effects of sweat loss induced by treadmill exercise on magnesium and calcium homeostasis in Franches-Montagnes horses

Abstract

The physological consequences of magnesium and calcium loss via sweat during a prolonged exercise test was investigated in eleven stallions. The test on a high-speed treadmill inclined at 3% consisted of 6 trot-intervals of 20 min each at 3.0 m/s. Blood samples were collected 1 hour before the exercise test, after each trot-interval and after 1 and 2 hours of recovery. The body weight loss ranged between 19 and 25 kg with a mean reduction of the body mass of 3.71% ± 0.45. Mean total magnesium concentration decreased continuously during the exercise and the first hour of the recovery period. Mean erythrocyte magnesium concentration decreased during the last two trot intervals and was significantly lower during the second hour of recovery. The mean total calcium concentration decreased during the exercise test and increased during the recovery period. Mean parathyroid hormone serum concentrations at the end of the test were significantly greater. Serum 1,25-dihydroxyvitamin D concentrations did not change with time. According to the results of the present study, additional magnesium and calcium supply are superfluous in the case of a single prolonged exercise. However, high dietary supply may be beneficial in hard working and heavily sweating horses to prevent the occurence of critically low ionised magnesium and calcium values.