Dogs and chickens don't mix IMHO. Our two shepherd have been trained to leave the chickens alone, but I wouldn't trust them without my supervision.
Our older GSD, Jax, has taken an interest in the two chicks we have in a brooder in the house. If one chick starts peeping loudly, he gets very upset and demands my attention to do something about it. Still, I'd never leave him unsupervised with the chicks if they were out of the brooder. Our late dog Charlie Girl wouldn't harm a flea. However she did get in the brooder when my brahmas were chicks and picked one up. She was attempting to take it to her bed, I'm sure to mother it, when I caught her. She dropped it when I told her to and the chick was fine, but that was just luck. Not every dog has a soft mouth.
I keep chickens and dogs seperate and I always will. That's what leashes are for.