What would be a better breed for protecting my chickens?

ok right now were having a problem with are chickens getting killed by coons,coyotes,foxes. and i have killed a few with my shotgun but i want something that will be there when im not. so what i was thinking was about getting either a rotweiler or german shepherd. i dont really what a long haired dog cause i dont feel like shaving him in the summer and the long fur just is a burden. so if you just tell me what breed you think would be good or any other breeds you have had exprience with. and no "my pitbull,lab,or beagle stories" i know there not sheepdogs.