We have barn cats that patrol the feed shed and the henhouse. They get fed every night and are so friendly they are annoying - (run up to the car like dogs when I get home, and I have never fed them!). However, they do keep the population down quite a bit. DH thought the cats were eating our eggs because the number of eggs dropped off a few weeks ago. I had to explain to him that the hens were molting. We DO see the stupid cats in the henhouse stealing some of the scraps we feed the chicken. Oh well. Since our hens are mostly game crosses, the cats wouldn't stand much of a chance if a hen really objected to sharing...
I had a pair of brother cats that we turned into the barn as kittens to get them used to it. Our hens actually adopted them 8/ The kittens slept in the henhouse with them every night, and helped keep predators away- never touched an egg either!!
Besides the one I got now, they were the best barn cats I've ever had because they doubled on duty LOL.