We have three dogs- two border collies and a pomeranian. The old border collie doesn't have anything to do with the chickens, just ignored them. The younger (3 yrs old) border collie is the protector of the flock. He lays by the run and just stares at the girls. If I let them out to free range he is right there with them walking very slow so as to not disturb them. I got 15 chicks 7 weeks ago and he was just msmerized by them. I was so tickled the day he realized that these little chicks were just a small version of his big girl flock. They girls were out free ranging, he was watching the chicks in their brooder cage, then he went out and looked at the older flock then came back in to look at the chicks. I swear, I could see in his eyes he just figured it out. Border collies are extremely intelligent and this border collie is a great protector.
Last weekend I put the chicks in their big coop and run. He came in to the big coopand laid down to watch the chicks. They peck his eyes and nose and he just turns his head. When he gets up to walk around he is in stealth mode, moving oh so slowly so he doesn't scare the chicks. It is really cute to watch.
The pomeranian is trustworthy with the grown chickens but not with any chicken smaller than he is.