Pyrenees will probably do the trick but you have to raise them where you want them to guard. We got two males as weaned pups and kept them in a chain link dog pen at the barn for about six months before letting them out. Now they guard the barn lot and everything in it. They are always barking at night. They are huge dogs and their barks sound even bigger. So far nothing bothers the chickens, ducks, geese etc. as well as the weaned calves. If you get them don't make big pets out of them, they'll be worthless. Feed them and treat them well but raise them around the animals that you want them to guard and they will do well. They have to have a job or they're just a nusiance. I see alot of folks in our area that have them but they keep them as pets and they do nothing but lay in the road and chase cars.