IRVING — The Cowboys made one roster move official, cutting safety Ahmad Dixon to get safety C.J. Spillman on the 53. The Cowboys agreed to terms with Spillman on Sunday, and swapped the veteran for the rookie from Baylor. They have five safeties on their roster.Dixon would be a candidate for the practice squad if he clears waivers.The Cowboys signed fullback Nikita Whitlock to the practice squad. He was an All-ACC nose tackle at Wake Forest but signed with the Bengals as an undrafted rookie free agent in hopes of making the transition to fullback. At 5-10, 251 pounds, he is too small to play defensive tackle.Whitlock’s signing leaves two openings on the practice squad. Offensive guard John Wetzel, who was released Sunday, could return if he clears waivers.