I agree with teach1rus! It's important to teach your dogs to be around the chickens, even if you don't intend to let them freely interact, because accidents happen- as you've sadly discovered- and they need to know that the chickens are OFF LIMITS. It can be done, and sometimes amazingly quickly - dogs are, for the most part, hard-wired to recognize a dominant leader and understand that leader's ownership of something. I have a new foster dog that has been here only 10 days (a weimaraner) and initially was absolutely INTENT on going after the chickens, and the cats... I now take him out with me, off leash, with the chickens free-ranging, and he avoids them meticulously, as do my other two dogs. Would I trust any of them unsupervised? No, not really. But the alternative is having to be always on guard, and this wasn't that hard to accomplish. I certainly wouldn't let anyone else's dogs around my chickens, though!