What do three promising young starting pitchers, 34-year-old lefthander Erik Bedard and a struggling bullpen equal for the Astros? A six-man rotation. After hinting at the move toward the end of a recent 10-game road trip, Astros manager Bo Porter said pregame Wednesday the club will use six starters for the foreseeable future. Rookie righthander Jarred Cosart (1-0, 0.96 ERA ) is set to start during a series finale against Boston’s Ryan Dempster (6-8, 4.54) at 7:10 p.m. at Minute Maid Park. He’ll be followed by Bedard, Brad Peacock, Dallas Keuchel, Brett Oberholtzer and Jordan Lyles, who started Tuesday during a 15-10 loss to the Red Sox. The club will [.]