What causes tying-up?
Tying-up can be subclassified as either sporadic or chronic exertional rhabdomyolysis. Sporadic exertional rhabdomyolysis applies to horses that, on rare occasions, experience an episode of generalized tying-up. A common cause of sporadic tying-up is exercise that exceeds the level of fitness. Electrolyte imbalances, especially low sodium, and deficiencies of vitamin E and/or selenium may predispose a horse to tying-up. Horses with concomitant illnesses, such as a respiratory infection, may also be more prone to tying-up than healthy counterparts. Horses that endure repeated episodes of tying-up, called chronic tying-up, may have limited athletic careers due to the start and stop nature of training schedules. Some horses are affected each time they exercise, while others might have only intermittent episodes. Over the years, chronic tying-up has been attributed to hormonal and electrolyte imbalances, lactic acidosis in muscles as well as vitamin E and/or selenium deficiencies, but few
