When I first got my chickies, my dog would have gleefully swallowed them whole. I used intensive classical conditioning and desensitization to get her used to being near them.
1) I put the chicks in their brooder, in their own room, with the door closed. My dog paced, whined and scratched at the door, anytime she looked away/left the door area, she got a kibble. I stopped feeding her from a bowl entirely for a while, and would carry kibbles in my pockets all day long.
2) Eventually I got to where she could walk by the door and ignore them. I put a leash on her, stepped on it, put a baby-gate across the door, and opened it. I started the process over again. If at any time she got too excited, I closed the door and walked away without a word. When I tried the next time, she remained calm much longer.
3) After a few days of this, she could sit calmly at the door and look in, and come away when I called her. I held on to her leash and let her into the room. (Note: my brooder was raised above her eye level, and she could only sniff the base of it) I repeated the process. At no time was she allowed in the room without me.
4) I continued with this system when my girls went out to the yard, in their coop, ect.
5) I sat my dog down and explained to her that these chicks were her pets, not toys, and she needed to be gentle with them and watch out for them. Laugh at me if you want, I believe in clear communication and intentions.
6) After 6 months, I trust her to be out with my fenced/free-ranging chickens on a long line under supervision. The chickens can run up to her, peck around her feet, and she will either walk away or ignore them. I will never get to the point where she will be with them unleashed and unsupervised, but I feel her progress has been tremendous.
One of the things that may have really helped was one time when Shadow stuck her head in the coop when I was in there, my Black Star ran up and pecked Shadow hard on the nose. Shadow pulled her head back, and ran away.
Shadow is a German Shorthaired Pointer/Lab mix. If she were a terrier, sight hound, or any of some other breeds, I don't think I would have gotten Chickens in the first place. I don't mean to offend other breed people, just my experience.
I have known some dogs that I could have probably trusted with my chickens no matter what, most of them were very well socialized and trained giant breed dogs.