Mary Tyler Moore, 63, has hitched her cart to the American Society for the Prevention of Cruelty to Animals in order to drum up support for protecting the horses who carry tourists on carriage rides through Manhattan. The actress, who keeps nine horses of her own on her upstate New York farm, told the Associated Press that she hasn’t ridden a city horse-drawn carriage since 1982, for a scene in the movie “Six Weeks.” “If I had known what these horses were going through, I would . . . not have participated,” she said. The ASPCA insists that the horses live in deplorable conditions and is proposing legislation to change that. Moore and the ASPCA are now looking for sponsors to support such a bill.