If your dogs are eating "poo candy", it might just be a habit, but it could be that they are missing something from their diet. Try using Missing Link on your dog's food ... a bag of it is rather expensive, but you only use a spoonful at a time, so a bag lasts for months and months.
We have a German Shepherd Dog, and he is great with the chickens. He never chases them, and helps put them in at night.
However, backyard breeding has done a lot to ruin the "working line" German Shepherd Dog. It's really hard to know what you're going to end up with, unless you've got a good...