Citing “financial challenges … faced in recent times,” the owners of Pimlico Race Course notified employees Saturday that they are shutting down the track’s off-track betting (OTB) facility by June 30 — the same date a key agreement for racing operations in Maryland is due to expire. In an e-mail to employees of the Maryland Jockey Club — subsidiary owner of the Pimlico and Laurel Park tracks — Mike Rogers, the company’s’ acting president, wrote that “this decision was not made lightly.”