About five weeks ago I took one of my dogs for a walk which we do regularly. One of her favorite parts of the walks is to go running and splashing into a shallow stream when I have her off-leash in the park (she is very well trained and has an instant recall, otherwise I would not let her off the leash in public). This particular day she must have stepped on something while in the stream that caused her a lot of pain on one of her paws. She yelped and kept on verbalizing her discomfort despite normally being a very quiet dog, and immediately came out of the stream. I checked her leg and paw thoroughly, but could not find the source of what caused her the pain. She stopped limping about a minute later and we continued on with the walk. Since that occurrence, she has not gone back into the stream on her own. I have to coax her a few times before she does so, and then only reluctantly. Just that one negative experience has caused her to no longer want to do something that she has enjoyed for over 7 years, since she was a puppy. She LOVED that part of the walk. Not anymore.
My point is that if it was my dog that was going after chickens, I would put a shock collar on her in a way that she does not realize it is being put on, let her run around with it for while so she makes no association with me putting something on her, then set her up with the chickens. Once she starts to go after one, I would immediately shock her with the highest level possible. I cannot imagine that it would take more than 2 shocks, 3 at the most, before she makes the association that going after the chickens is going to cause her strong discomfort, and she will leave them alone thereafter. It is how they also keep dogs from going after rattle snakes. Aversion therapy can literally save dogs' lives, or keep them in their current homes., whatever the case may be. It's worth the time to set the dog up, and worth the bit of discomfort for the dog for that short time, IMO.
It is important to have a quality shock collar for such a lesson. The timing of the shock matters a lot for the dog to understand quickly. I have heard that some of the cheaper collars can have a slight delay which can be confusing to a dog.