We have 2 adult dogs, a german shepard that killed a young pullet once, but i believe she was actually trying to play with it, and a Lab who snarls and snaps at EVERYTHING in HER yard. It took about a year of VERY slow integration, with the chickens safely behind a barrier for most of the time before we got to where we are comfortable that the dogs and chickens can be out together, but only if supervised(mildly).
Like I said, start very slow with introductions behind a barrier, praise the dog when they start to ignore the chickens, a stern "no" command if they start to show aggression. Make introduction sessions very short to begin with and very slowly increase the length of time the animals are together. Very slowly increase the exposure, as some have said, go from barrier, to leash to off leash tight supervision etc. If you see aggression, step back a bit and give them more time.
It can be done(depending on the dog ) but will take work.