Exercise-induced intravascular haemolysis in standardbred horses

 In human sports medicine a pathophysiological condition called `sports anaemia' is reported. This condition has been attributed to episodes of intravascular haemolysis induced by physical exercise. The occurrence of haemolytic episodes is indicated by the presence of high values of free plasma haemoglobin and lower plasma levels of haptoglobin after physical exercise. The literature regarding sports anaemia in horses, and in particular haemolysis induced by physical exercise, is rather limited. The purpose of this study was to evaluate the markers of intravascular haemolysis (plasma haemoglobin and haptoglobin) in Standardbred horses immediately after a race, in order to ascertain the presence of intravascular haemolysis, possibly induced by physical activity. We reported both the haptoglobin and free plasma haemoglobin values as a percentage of the total protein to avoid any influence of haemoconcentration induced by the exertion during the race. Free plasma haemoglobin concentration showed a significant increase both at 5 min (p < 0.01) and 10 min (p < 0.05) after exercise. A significant decrease in the haptoglobin occurred in both post-exercise blood samples, and was statistically significant 10 min after the race (p < 0.05). These data suggested that episodes of intravascular haemolysis may occur during physical activity in Standardbred horses.