I don't believe that it's a matter of get rid of the dog or the chickens. Some dogs can be trained. It's easier if you can start when they're pups, but it doesn't always work out that way. It will take time, patience and consistency. Your other option is to reinforce your fence, get a kennel, or tie your dogs out so they don't have access to the chickens. Build a safe, secure run for your chickens. Let the dogs out while the chickens are in the run, put the dogs up and let the chickens out. It's not the "taste of blood" that keeps the dogs going after chickens. It's lack of training, and the temptation of another feathery, squawking, flapping squeaky toy. You need to train that out of the dog, or keep them separated. I'm glad your neighbor is being understanding. They may not be, though, if it continues.