LEXINGTON, Ky. (AP) - Breeders' Cup chief executive officer Greg Avioli has resigned. Avioli is leaving the organization after five years as the head of the group behind horse racing's biggest event to take a job with a new racing and gaming company. Breeders' Cup chairman Bill Farish says the search for Avioli's replacement will begin immediately. The Breeders' Cup went through a series of major changes under Avioli's leadership, including expanding the event to cover two days and 14 races in all. Farish said Avioli played an integral part in the making the Breeders' Cup a stronger organization. Avioli said he was proud of his work with the Breeders' Cup and is eager to take on a new challenge.