We've got a little dog named Jasper who looks just like yours he's a teddy bear, shitzhu bicon cross. He is mesmerized by the chickens he just stands by the fence and stares at them, which scares the bejesus out of them and they run for the coop, I don't think he would really bother them, it's my wife's pomeraninan who is the trouble maker she charges the fence snarling and barking and really scares them. I am planning a good rooster encounter for her. She's got a big bark but I think if a big red rooster came after her she'd be runnin for the house in a hurry