Years ago when I helped take care of a milk cow, we put turkeys in the same pasture. Not only did the turkeys scratch the cow pies completely away, looking for corn and maggots, but they also followed the cow around and picked off the big horseflies that tried to
land on her! Eventually it got so that the cow would lie down and the turkeys would walk on her after the flies! I would imagine chickens or guineas would have done as well, but we wanted a place to keep the turkeys that was completely away from the chickens......