Edgar Prado will take over as the rider on Machen when he runs next in the Louisiana Derby on March 26 at Fair Grounds. Jamie Theriot had ridden Machen in his previous starts, including a fourth-place finish last time out in the Risen Star Stakes on Feb. 19. Theriot was scheduled to go to Dubai on March 26 to ride Chamberlain Bridge, who is trained by Bret Calhoun, in a rich turf sprint there. But before that trip was canceled this week, trainer Neil Howard and owner Don Adams of Courtlandt Farms reached out and secured the services of Prado, who has ridden often for Adams over the years. KENTUCKY DERBY NEWS: Track all the 3-year-olds on the Triple Crown trail “We waited as long as we could, but we needed to explore our options,” Howard said. “We had lined up Prado before they had trouble with the shipping arrangements with Chamberlain Bridge. It’s an awkward situation. Fortunately, Jamie was very nice about it when I spoke to him.”