I believe the most essential part is to have very good control over the dog's first interactions with chickens. I have two border collies (trained to herd sheep) and a GSD/Aussie mix. They are fine when I am out there with them (one of the bc's deliberately turns so her tail is facing them she is trying so hard to be good. The other has helped me round them up to the coop.) I don't trust any of them with the chickens loose unsupervised. They can practice agility or herd sheep with the chickens running around just fine. Herding dogs are a hazard to livestock if they don't have a job to do. That said, they don't dig under the pen or obsess over killing the chickens the way other dogs do. The GSD mix goes out and does a patrol of the coop and yard to make sure everyone is where they are supposed to be. They can all be out with me off leash with the chickens free ranging without incident.
Another friend of mine with bc's has two that are fine and one ate a chicken. All herding bred and trained.
A friend's dog, who is a mix of cattledog, collie, and ? that is in training to herd sheep has very evil thoughts regarding chickens. The dog is very well trained - he does agility, flyball, herding, tricks, even works as a movie dog, and is around other small animals without a problem, but chicken = sic 'em.
Don't know if that is a help or not, but that is a sampling of my experience of herding dogs around chickens.
My cat has pried open a window, pushed out a screen and vaulted a 6 foot fence to stalk chickens.