My favorite dogs are All American (mutts). They make the absolute BEST pets.
My favorite actual breed is an Alaskan Malamute (wonderful, wonderful, wonderful dogs...can't say enough good about them).
I only adopt rescue dogs. I would encourage anyone to check into rescue dogs first. There are just too many wonderful and amazing dogs out there who need a home.
As far as chickens and dogs...I have 3 All American dogs. The smallest is around 25 lbs and we have absolutely no idea what she is. My other two are beagle/terrier mixes, one is about 40 lbs, the other about 47 lbs. My smallest dog is a rescue and she was raised around chickens. My other 2 dogs were adults (around 3 years old or so) before I got chickens. It took us about 2 weeks to train them to not bother the chickens. My chickens and dogs roam together, play together, and nap together. I have never had even the smallest of problems, EVER. That said, my dogs are very laid back and have great energy. They are also exercised well, so I think this contributes a lot. Also, my dogs are honestly just GOOD dogs. I could not ask for better dogs. My 2 beagle/terriers have even been trained so they don't chase squirrels, rabbits, or birds.
Get a rescue dog...you will NOT be disappointed !!