I opted for a GSD because a donkey will hurt your goats if he/she doesn't like the goats. I know you're looking for protection for your chickens but I thought it was worth mentioning. If they don't feel bonded to their charges, they won't protect them. The reason why they are pretty good at protecting is because they don't like dogs or coyotes. Also, yes, they can be dangerous to you if they're protective of their charges.
But a LGD will protect your livestock from all kinds of predators, not just coyotes and dogs. They're also easier for a human to handle.
Puppies also need to be trained. Please don't get a puppy LGD and expect him/her to fill right into the job, or to not chase chickens. They still need to be trained. You might get lucky and get one already used to being around livestock and knowing how to behave. But don't trust them without training until you're sure. It's great when the breeders keep the puppies out with their parents patrolling, but note that they don't all do that.
And FYI, I got mine as a four-year-old. I don't know much about her, but I do know that she was already used to being around all sorts of livestock. So she's fowl-safe, as well as goat, cow, etc. safe. She hates my housedogs too, and that's the way I want it. I keep them totally separate. And when the house dogs get too close to the goat pens, she growls and barks at them and holds them back. Which is what she's supposed to do.
And FYI, they are very noctural. It looks like they're lazy good for nothings during the day, but believe me, they're just conserving energy
They are up alllllll night patrolling, guarding and yes, barking...all night, esp great pyranese. So if you live close to others, you might want to consider a quieter LGD.
