I have 2 bros, half aussie, half border. For the first few months after we got them as puppies, no problem, then some issues began. At the vet clinic, happened to be a retired sheep dog trainer, he took a liking to the boys and offered to come over and train me to train them. Best two hours I have ever spent. He told me patience, and trust the dogs' intelligence and willingness to learn. It takes time, lots of time, and positive reinforcement, LOTS of treats. So, sat with them for an hour or two every day with chickens out. No leashes. Every time they sat still and just watched, Good Boy verbals and treats, but if they started to move towards them, "Leave it!" and brought them back to where I was sitting. More treats. If chickens approached, which they did, treated the pups when they sat but if they budged, Leave it, bring back, then treats. It was over and over and over. For almost two months, I only let my chickens out when I was in the back yard with the pups, or if they pups were in the house. Anyway, we did this training every day for about two months, and then I let them all free together in the yard, but kept very very close eye and if it looked like either of the pups was regressing, then sat with them in the yard and reinforced the training. It was maybe a month or two after that, I felt comfortable enough to trust them - and their training. Now, they are 7 years old, lots of chickens absolutely no problems and in fact those dogs protect the chickens like you can't believe, raccoons are regularly treed. Positive reinforcement, no physical punishment, and lots of treats (buy in bulk, it will save you $$$). Hope this helps!