The filly, born Jan. 12 at Burleson Farms near Midway, Ky., was out of the Hawkster mare Zophie, dam of 2006 Spinaway Stakes (gr. I) winner Appealing Zophie. Lyn Burleson, owner and general manager of Burleson Farms, said the foal suffered a “paddock accident” Jan. 24 and was euthanized Jan. 29 after the injuries were “not repairable.”

The filly was owned and bred by Don and Becky Ming.

“It’s just a terrible tragedy,” Burleson said. “You just never know what can happen.”

A classic winner of seven grade I races, Curlin, a son of leading sire Smart Strike  , is North America’s richest racehorse with earnings of $10,501,800. Curlin stands at William S. Farish’s Lane’s End Farm near Versailles, Ky., for a 2010 fee of $40,000.