My Australian Shepherd was a problem for awhile. She managed to kill 4-5 of my free range flock before I got super disciplined on her and it worked. She was just at year old when she started getting the chickens, before that she'd not even really notice them until she "snapped" one day and started killing chickens. After a bit of discipline (that did not seem to work) I started pinning her up all day long in the chicken run while my chickens were out free ranging. She'd be put in the run when I let the chickens out in the morning and then she'd be let out in the evening once the chickens were in the coop for the night. Every evening for 2-3 months I put her on a leash and would spend around 30 minutes disciplining her and teaching her "no" while walking around the yard. If she tried to pull me on the leash I yanked the crap out of it and gave her the "no" command. I tightened up the leash so she could only walk right by my side. Every time she tried to take off I yanked the leash and reinforced the "no" command. At the end of each session I'd unhook the leash and see if she'd stay by my side or bolt off to do something else. I knew we'd go through this entire process daily until she would not bolt off or run away....that took at least 30 days. I'd even change directions abruptly and if she was not paying attention and kept walking to a tight leash then I'd yank her leash. I wanted her to have to pay attention to me 100% of the time and what I was doing. After 30 days and getting her under control I then started letting her out earlier while the chickens were still out. I'd still use the leash but now we'd just hang out around the chickens for 30 minutes or so. I had her "sit" and "no" commands instilled in her and now it was time to teach her that the chickens were off limits. Took about two weeks at 30 minutes a day to break her from wanting anything to do with chickens by yanking on that leash when she wanted to go after them. It's been well over a year since I worked with her and she's one with the chickens in the universe...they even steal a bit of dog food from her while she's eating. One thing for sure is that neither one of my dogs will even look at a chicken when one is close, they turn their head/gaze away from them. I didn't train them to do it, they just know that the chickens are off limits and that they better just look away to resist the temptation. Whatever you do only use the command "no" (or whatever) when you have to. I do not overuse the word. When I call them by name in an authoritative voice they simple stop whatever they are doing, sit, and then look at me. When I yell "no" then you better not be in their path to get under the shed because they will run you over. They seek shelter under the shed from the incoming artillery that comes with "no". The command "no" in an authoritative voice finds them whimpering under the shed for about an hour each time. They know they have messed up. They just wine, mope, and pout for an hour then eventually come out once their feelings are no longer hurt. I have dogs for a reason and they need to earn their keep. I train my dogs to earn their keep and in exchange they get to live on a rural property that all dogs dream of. They are free to laze about wherever they want within 3-4 acres of "yard" around the house, get fed great chow, and get loads of attention from my family of 5...but they have a job to do. Train your dog, make it do what you want it to do. If it can handle those tasks and obey commands then it is rewarded to do whatever it wants in it's spare time. Dogs serve a purpose, they are a rural family's first line of alert and defense, they also guard over our livestock and critters. Train them with a firm hand and you've made a great investment for 8-10 years. Takes some effort but is well worth it. Good luck.