So sorry to hear that frustrating news.I am so mad at my dogs right now!!! We had worked very hard to make our Aussies chicken friendly. My girl now loves hanging out with them, even breaking up rooster fights and when a layer goes rogue and lays somewhere in the bushes or field, she is very quick to helping me find nests.
Our first Aussie that we have bred and mine is the daughter of had pups early this summer. My dad decided to keep a male (he's so cute). Well, in the last two weeks, he has killed four chickens (all females) (why not any of my overabundance of roosters...) and mauled our Thanksgiving turkey so bad that my dad had to put it down. I can't confirm or deny that the girls helped him in taking down the turkey, because the bird was bigger than the dog... Even though our girls have been excellent with the flock, nature will take over at some point and they will do what a carnivorous animal would normally do!
The dogs are normally let out in a fenced in yard so they don't have access to the chickens. We will let them in with the flock if we are there to supervise. I had been working really hard on the pup so he didn't chase or try to attack. Even after doing what old farmers tell you to do, he is not doing any better. So we have decided to have him move on to a family that doesn't have farm animals and can really focus on him. Hopefully I don't have to do too much work again with the older dogs.
Ugh... thanks for letting me rant!