I have a Blue Heeler. He is now safe with the chickens and takes his flock-protection duties quite serious. If they growl or let out any kind of "hey-what-is-that"noise Jake is out the door and running a perimeter around the flock. He checks the sky and the ground and then comes back to the house. But....he took a lot of training not to chase the girls or to bat them about.
If you look at chickens from a dogs eyes they are play toys. The worst Jake ever did was flatten a hen (right at my feet too) with his paw on her back and then shove his nose up her bottom for a really good sniff. He immediately let go when I told him to "leave it" but she went into shock and didn't really come out of it for about a week. She just stood around and wobbled and a little saliva came out of her mouth for a few hours. She finally recovered and was fine.
He is handy to have around when a rooster acts up. You just point and say "get him" and Jake chases the rooster off and he then leaves you to your chores. If he is out with the hens and a little bored he will herd the roosters around. I don't know how, but he leaves the hens alone and picks out one of the three roos and will just move him back and forth.
But it took a lot of work to trust him with the free range flock. We had a half blue heeler stray that was an amazing dog with the first flock of chickens. When it was time to put them up Blue would round them up and herd them into the coop. The most amazing part was the fact that he was 100% blind! When he died we ended up with a full blooded blue heeler puppy.
Jake was raised with my third addition to the flock, about 40 peeps. They started to range around 4 weeks and Jake was there with them. You had to be with him at all times to keep him from getting out of hand. I wouldn't recommend a heeler to anyone that doesn't have a lot of property and a lot of time. He is a very intelligent dog, a little too smart. He keeps the yard free of predators and watches the sky as well. He needs a lot of exercise and some days I don't think he ever tires out. And he really didn't mature until this year, he just turned three. It's been a long ride, but he is now a great protective companion.
As for a Husky, they are the closest to a wild wolf, I wouldn't ever have one with a flock of chickens. And a Labrador I know raided the neighbors chickens and brought one home. Sure they have a good soft mouth, that is because they retrieve BIRDS for hunters. Any dog is going to think chickens are play toys and will need trained, but I wouldn't go with any dog that his history has birds or retrieving in their breeding. Herding dogs need exercise and get bored easily, but are intelligent and trainable.
I love my heeler and don't want anyone else at my side.