I started to introduce my chicks to my dog when they were about 8 weeks old. First, I kept them in an inclosed run away from the dog, and every time he showed to much interest I would make a *shht* sound and tell him to 'leave it'. Then I slowly would let him spend more and more time with the chicks and now they are fine together. Of course, the chickens are still a little timid around him, but they know he won't do harm. One of the chooks even will seek out my dog to hang out with him!
But even though they are fine with my dog, they are still very afraid of other dogs and cats.
I think that it is better to have your chickens used to *your* dogs, so that they won't run away and initiate prey drive in the dogs, but not introduce them to too many dogs, so that they still keep some of their instinctual fear.
For me, there is no downside to introducing my chickens to my dog. He will run outside and guard the chicken food from squirrels [although sometimes he eats it himself
]
And he will protect them from the neighbors cats.
I would also recommend to introduce them when they are still young, as I find it to be *a lot* easier, because they kind of accept the dog as part of their flock from the beginning. If you wait until they are older, then they are generally a lot more afraid of dogs, as they didn't grow up with them.
Also, when you start to introduce the dogs to the chickens you will need to supervise them 100% of the time! We did not let my dog be alone with the chickens without supervision until a couple months, when we were sure that he would not hurt them. Of course, it all depends on your dog and their personality!
Best of luck!