Top American sire put down Unbridled, America`s champion three-year-old colt of 1990, was put down on Thursday after suffering a severe bout of colic.The 14-year-old stallion had undergone surgery at the Hagyard-Davidson-McGee veterinary clinic near Lexington last month and was later treated at Claiborne Farm near Paris, Kentucky, where he has stood since 1997.He was then sent back to the clinic where it was discovered that the symptoms rendered his condition inoperable, it was reported on the Blood-Horse website.Unbridled won the 1990 Kentucky Derby before landing that year`s Breeders` Cup Classic and since his retirement from racing has proved a success at stud siring 24 stakes winners to date.
