I see several problems here. 1 - your dogs have access to your chickens. 2 - apparently the dogs have not been trained to leave the chickens alone. 3 - oftentimes several dogs, even though they are tame, will act as a pack and chase and kill things. I'm sorry for your loss. But you are going to have to change some things if you want to have both dogs and chickens. Chickens run, flap and squawk. Dogs like to chase and play with things that run, flap and squawk. If I had to choose between one or the other, I'd have a dog. But that's just me.