My very birdy Irish Setter jumped over a low fence and managed to open the latch to the chicken run area....he chased them out into the yard but didn't kill any of them. He helped himself to their snacks and more then his fair share of poo I'm sure. I was on the phone for 15 minutes so I think if he was going to hurt them he would have in that time. Still, I'm changing the latch on the run door. His father is an escape artist and can get out of any kennel, open any window and sliding glass door. Smart but oh so aggravating. Whew. I would have been so upset, I have been raising these chickens since they were only a few weeks old and now two of them are about to lay finally...the other three will in a month or so. I'm so glad I don't have to start over. My rooster did his job, he protected the girls and had them under a low bush by the fence, then he chased them back into the run after I grabbed Flynn's collar and put him in the house. I'm attached to these guys, I'm so glad they are OK.
I have had just about the same thing happen to me. My dog (german shorthair pointer) that we hunt with figured out how to unlock and open the door into the chicken run, and I wasn't as lucky. She killed my sultan pullet and injured two of my hens. Sounds like a great rooster. I wish I could have a rooster sigh someday...
whew! I've got one that wouldn't even bother to chase the chickens out as long as he could get to the food, but the other............... I'm so glad your dog went for the food.