Hi my missus fosters greyhounds and lurchers for a charity. We constantly have 4+ dogs in the house and have a mini flock of 11 hens.
from my experience if the dog doesnt go for the hens the hens will ignore the dog unless you nail some food to its collar ;D
Our own dogs come into the pen with us and the worst incident weve had after 3 years is a pecked dog and a rat hunted down and killed!