You mentioned that your chickens can't free range. Are they in a pen of some kind? Do you have an enclosed run attached? I don't know what kind of dogs you have but chickens are at the low end of the food chain so a dog has instinks to go after them. They can be trained, taught that these birds are "part of the family". Dogs, cats, raccoons, skunks, owls, hawks all are predators to chickens and/or their eggs. It sounds like an enclosed run would solve a lot of problems at least until everyone gets to know each other. We made one with 2 cattle panels, and 2x6 lumber. That's another thing you can google and get an idea. You can click on my photo album and see the cattle panel whoop run with my peeps in it. I'm afraid your dogs might inadvertently hurt your hens before they learn "NO"