I got chickens when I had pitbulls and a mix breed (ready for this, she was a cocker spaniel, spitz, german sheppard, lab). They were old and once the chickens were introduced as part of their family they never messed with them. But let a cat come in the yard and you would never see that cat again.
After the Pits and my mixed girl passed I got my two black Cocker Spaniels (brothers). I got them as puppies and were taught from the get go. When they were less than a year old one accidentally ran into one of the chickens (Maude) and broke her leg. So besides that one vet bill and the chicken being in a cast for weeks on end I have never had a problem with the Cocker's. Let them see a squirrel and the chase is on.
The main thing would be if you are going to get a dog, try to get a puppy and teach them from the start. That way they will know that the chickens are part of their pack and protect them instead of thinking of them as lunch or a toy.