My cats were taught by a very protective Mama hen with 10 chicks that they should not mess with her chicks ever. That lesson carried over to the other chickens.
My bichon frise yorkshire terrier cross had to be taught. She wanted those chickens. I had to keep her on a leash until she learned to not chase. It does help that the Cochin rooster was bigger than her so intimidating with just his size. However I took my dog to a friend's house and apparently she felt those chickens were fair game for chasing. Now I keep her leashed when we visit.
My bichon frise yorkshire terrier cross had to be taught. She wanted those chickens. I had to keep her on a leash until she learned to not chase. It does help that the Cochin rooster was bigger than her so intimidating with just his size. However I took my dog to a friend's house and apparently she felt those chickens were fair game for chasing. Now I keep her leashed when we visit.