Some dogs cannot be trained, some can. Start by assuming Milo is one that can't, and create a barrier between him and the chickens. What you use will depend on your situation, sometimes something as simple as plastic poultry fence will work, some dogs need something much stronger. When the chickens are separated from him, start working on obedience, AWAY from the chickens, so he can concentrate on you.Then, ON A LEASH, start letting him go up to the chicken barrier, and look at them, then call him away and reward him. If he won't come away, increase the distance until he is able to focus on you again, then gradually come closer to the chickens until he can be called away every time, even with his nose to the fence. Then, and ONLY then, start having him on leash, with the chickens loose, and call him to you. Do not ever force him to come to you, it needs to be his choice, or he will not be reliable off leash. Don't rush it, and don't ever let him chase them, or he'll learn it is fun. This means, fix things so he can't "escape" and get to the chickens. Some dogs learn fast, or get bored with the chickens, and some dogs can take months or years, or are never safe to have loose around prey animals. Good luck. Stay positive, but assume the worst.