There are breeds called livestock guardian dogs (LGDs). Great Pyrenees and Kuvasz are examples. They are usually used to protect larger animals but people have used them to protect chickens. It would take a lot of work to rear a pup and train them so it is a pretty serious commitment. From what I've read they need a lot of space, they can be very protective (so you have to be careful with visitors, mailperson, etc.), and they bark a lot. From what I have read LGDs are usually full time working dogs, meaning they may be thought of as pets but they live with their herd/flock all the time.
I don't have an LGD but my cattle dog X is very protective of the chickens. She often watches the yard while they are free ranging and chases away any animals - cats, raccoons, opossums, and even the dreaded squirrel (we're in the city). She can hear raccoons from inside the house at night and has woken me up on many occasions to chase them away. But I would by no means call her an LGD.