The powers-that-be at Dunkin’ Brands are getting a pat on the head from People for the Ethical Treatment of Animals. The animal-loving organization is applauding the Canton-based owner of Dunkin’ Donuts for its stand against the dehorning of cattle. According to PETA, Dunkin’ Brands is the first restaurant corporation to ask its suppliers to begin breeding cattle without horns to make dehorning unnecessary. (The practice, which sounds fairly ghastly to us, involves burning out cattle’s horn tissue with hot irons or chemicals or removing it with a sharp implement.) Several celebs have endorsed PETA’s campaign against dehorning, including Cambridge-bred actor and outspoken vegetarian Casey Affleck, who narrates PETA’s unsettling video exposé of the practice.