Unfortunately, as the saying goes: Man's best friend is a chicken's worst enemy.
Don't be too discouraged yet. I live in a rural area and when we bought our property there was a stray dog that was completely wild, probably let loose as a pup, that was completely afraid of humans, and was probably living off whatever it could kill or scavenge. After 10 months of leaving food out for it we eventually developed a good relationship with her. Later, when we got chickens, we could see right away that chickens looked like mealtime to this wild dog so we kept the chickens confined at first. The first time the dog saw them, she went straight at them but I grabbed her and gave a very stern yell and muttered some serious words to her to give the message that the chickens were off limits. We did break this wild dog of its predatory ambition very early by getting very angry with her if she even looked at the chickens. Eventually we felt comfortable enough to leave the chickens out and would even let them loose while watching the dog very closely and giving her a sharp "HEY" whenever she got too inquisitive. One day I came home and a strong wind has collapsed the gate and my first thought was that all the chickens would have been destroyed. I was happy to find that the dog was there laying down there and the chickens were in the yard all unharmed.
One thing to consider was that we had an agressive rooster at the time so the dog may very well have been attacked and learned to stay away.
But I honestly think the dog understood the relationship of the chickens to us and chose not to harm them. Eventually, the chickens were let free all the time. Our stray never bothered them and was great at keeping coyotes away.
Another thing to consider is that even a solitary dog will act differently when in a pack. Our stray was completely antisocial to all other animals so the pack mentality never had a chance to kick in. But 2 dogs together - if one attacks, the other may join in the frenzy. So be very careful. Bird dogs such as labs are also harder to deal with because of their breeding.
Introduce early and maybe keep them separate by a fence for an extended period. Watch for any attention to the chickens and correct them immediately with a stern voice. There are many people who have plain ole muts that do well with birds, but additional care and attention is necessary. A flighty fluffy bird can be like a toy, even though the dog means no harm. That is one reason NEVER to play catch games with your dogs. You will be rewarding them for predatory behavior. They may not ever be trustworthy enough to leave unsupervised but you may be surprised.
We have a Maremma now so there are no issues. They all eat, hang out and even sleep together. But a Maremma has breeding to not have a prey drive. He sees the bird as his charge and his will is to guard them.
