Mummify, a six-year-old gelding and winner of more than 5 million Australian dollars (US$3.7 million, Ђ3.1 million) in career prize money, had to be destroyed after suffering a serious leg injury while finishing third in Saturday's Caulfield Cup.
Mummify, trained by Lee Freedman, won May's Singapore Airlines International Cup and was trying to win the Caulfield Cup for the second time in three years.
But the horse broke down 300 meters (yards) after the finish line and a veterinary check revealed he had shattered the sesamoid bone in his near foreleg.
The horse, purchased by John O'Neill for just A$40,000 (US$30,000, Ђ24,900), was treated at an animal hospital near Caulfield race course, but was later put down.
Jockey Danny Nikolic, who rode Mummify to his Caulfield Cup win in 2003 and the Singapore victory this year, was also aboard the horse on Saturday.
Railings, the four-year-old son of champion sire Zabeel, won the Caulfield Cup, with Japanese horse Eye Popper second.
A crowd of more than 52,000 watched the 2,400-meter race, one of the major meetings held before Australia's biggest horse race, the Melbourne Cup, on Nov. 1.