What is a LGD? It is a breed of dog (there are several) that is specifically designed to have the temperament to live amongst livestock, large and small, without feeling the need to hunt said livestock. Additionally, they develop a sense of ownership of their flock or herd and will protect them against predator attack. They are often very large in size, which makes them appear intimidating. In the case of the Great Pyrenees, you will get a very fluffy white or white with spots or bandit markings type dog. Our two happen to have the kindest of hearts and most loving demeanor you could ever hope for.
They are not inexpensive to keep nor are they without challenges. They eat a large quantity of food relational to their size, they often require stout fencing as their heritage calls on them to wander, they need plenty of space for exercise and grooming should be done regularly to keep their thick fur from becoming matted and unmanageable.
That all being said, we have had great success using LGD's to protect our flock. They keep roaming predator animals at bay not through direct confrontation, but by regularly patrolling our property and leaving scent and other clues to passersby that THIS is not a place to hang out. For stealth predators such as raccoons and opossums it will still be necessary to maintain secure coops and housing as poultry are vulnerable 24/7 to predation and you'll want as many layers of protection as possible to maintain a safe and healthy flock.