We got our 7 year old Border Collie-American Pit Bull Terrier, Cooper, one year ago this month. He was a shelter dog, in and out of shelters for his whole life I think. The adjustment to a consistent, loving home where he's NOT in charge, moved slowly but steadily. We got a professional dog trainer this summer and that has helped him and us a lot.
His first reaction to the 13 hens in the coop & run was to run circles excitedly around the coop/run. Typical border collie, trying to "herd" them.
Everyday we walk past them (always in coop/run/secure yard) during our long walk to the back of our property, on leash. He goes out with me when I feed them daily and clean the coop on weekends. Now he is definitely de-sensitized to them and essentially ignores them. He sees them day in and day out...old hat.

This past weekend he waited for me while I cleaned out the coop with the coop doors fully opened. Seven of the girls were more interested in checking him out than he was in them. In fact, he was focused on barking at a dog on the neighbor's property, while the chickens clucked away at him.

He was oblivious to them. Don't bother me, I'm barking at the neighbor's dog!
The best part was when Cinnabon jumped up on the door ledge and launched into an egg song. Her bestie Zippie was in the nest box and was laying, so Cinnabon wanted to announce it to the world. I'm going to try to post the video I took of that whole scenario. In case I can't let's just say it was priceless. (Cooper hears their egg songs everyday - ain't no thang to him)
Having said that, we never forget that Cooper is, in fact, a dog. There are never any guarantees that his dog/hunter instincts would not suddenly kick in. So we make no assumptions, just because he's "fine" with our girls and he's a good (reformed) boy. He's still a dog.
Let's see what I can attach. Nope, not the compressed mp4 file. Dang.
#LetsGoBrandon