Value and type of dog is a function of situation. Free-range birds will benefit. Larger flock covering larger area will benefit more. If dog also valued as pet, then range of breeds suitable but smaller breeds may have problems with larger dogs. Most losses not caused by other dogs are most likely to be at hands of raccoons, oppossums and foxes. First two will be active at night while latter will be out at anytime. At night chickens are afforded some protection by cooping / roosting system and dog can make so predators do not have enough time to break in. Any dog with suitable attitude and greater than 45 lbs can handle those predators. Hawks and owls are very easy for medium to large dogs to keep away so long as dogs are active and able to get to predator if and when it get at birds. Coyotes are fun to talk about but they are not nearly as problematic as first three mammals if dog is at least half again as large as they are. Coyotes seem to respect larger dogs more than a sneaky little red fox will.
You will not be able get enough information about value of dog by just asking about breed or training method. Other considerations such as confinement systems, make-up of flock, types of predators, and your management system must also be considered. iF you start with a pup, then you will be a year or more before dog can deal with predators tuffer than oppossums, hawks and owls. Some dogs never get tough enough to deal with some predators and that is a mental issue. Training with respect to predators can help or hurt. Four parties will be learning for success to be realized; you, dog, poultry and predators. It takes time.
You will not be able get enough information about value of dog by just asking about breed or training method. Other considerations such as confinement systems, make-up of flock, types of predators, and your management system must also be considered. iF you start with a pup, then you will be a year or more before dog can deal with predators tuffer than oppossums, hawks and owls. Some dogs never get tough enough to deal with some predators and that is a mental issue. Training with respect to predators can help or hurt. Four parties will be learning for success to be realized; you, dog, poultry and predators. It takes time.