No, a Newfoundland is not a good farm dog. Although Newfoundlands are good watchdogs for you and your family, they do not make good livestock guardian dogs.
Newfoundland dogs are friendly, gentle dogs that love companionship and make great family dogs. They prefer to remain inside to be around the family, and don’t do well living outside with the livestock.
Because Newfoundlands have such a gentle nature, they aren’t as bold or brave as typical livestock guard dogs. They won’t proactively scare away predators that are after your livestock.