Gender differences in exercise – induced intravascular haemolysis during race training in thoroughbred horses

Exercise-induced intravascular haemolysis and “sport anemia” are widely reported in human sports medicine. It has been recognized also in horses, however, the clinical importance and the onset of this condition seem different than in human. In this study we investigated the episodes of intravascular haemolysis, indicated by the increase in plasma haemoglobin and the decrease in serum haptoglobin levels, after routine training sessions in race horses. Heart rate and changes in haematological parameters confirmed, that the exertion was relatively high. Intravascular haemolysis did not appear in stallions but was detected in mares after two training sessions. It has been determined that serum haptoglobin levels were higher in mares than in stallions before and after all training sessions. It is postulated that intravascular haemolysis induced by training is of limited clinical importance because it occurred only in mares which are better adapted due to higher haptoglobin level at rest, and it had no cumulative effect. Therefore gender differences should be taken into consideration in experiments with athletic horses.