Edited sentence: It is estimated that there are 1½ such accidents for every 1,000 race starts, roughly 2 per day, or the death each year of 700 horses.The genetic makeup of today's horses may have led to the fact that the thin ankles of highly-bred horses are ill-fitted to sustain the average 1,000-pound weight of the horse's body.The problem has yet to be addressed by the horse breeding/racing community