Poison, traps, glue boards, cats, terriers, they all work to some extent. You cannot ignore the problem, or they will completely take over your coop, barn, and even house.
I live several blocks away from a large grain elevator. They have poison out at all times, and lots of rats. I have never seen a dead rat, and our dog sometimes goes there when I visit them, and he's never found one either. Seems that they always go into their burrows to die. I use poisons around my birds too, and have never seen a dead rat, and I know by the missing poison that it's being used.
I also have a great Rat Terrier. He's great on killing them, and I would recommend one for anyone.