My two cents ...
Having a dog from breed know for guarding will get you off to a good start. A lot will depend on the individual dogs temperament. To guard our delicate livestock the dog needs to gentle with the birds and needs to have a desire to protect them. I can definitely see a German Shepherd or other guard dog or Livestock Guardian Dog (
www.LGD.org) working out well. Any dog will need training to accept the birds and to accept the job of guarding the chicken yard. Qualities you will need are:
Guarding breed (
www.dogbreedinfo.com)
Independence (test the dog for this?)
Weather proof (for your area)
Limited predator instinct; good with small animals and kids (a shelter cat aggression test may be a good indicator)
My current defenses consist of a fenced in area and dogs to guard the area. I have four dogs. Three of the dogs are from hunting breeds. I find them mostly useless for guarding the property, except for joggers. I am well protected from those chicken stealing joggers. These three are more focus on their people and usually hang around the house.
The fourth dog is a Great Pyrenees. She is excellent. She has a completely different attitude than the Labs. Often I find her just sitting on a high part of the yard, looking over everything and occasionally barking. I think this thundering barking to mark the territory is useful and important in deterring predators. Pyrs are also very self-sufficient and weather proof, so she doesnt sit at the front door whining to get in. She is happy to sit on a snow mound and chew on a stick (or ice as the case may be. Shes one hot doggy).
One issue with the Pyrs is that they mature slowly, so puppies take a while to train. But, by two years they begin to mellow and with the right training are happy to not chase the birds. So, you might consider a Pyr thats 1.5 years old.
Fencing is also critical for a Pyr. They tend to roam. Five foot high fencing may be necessary. Barking is another issue with Pyrs, but also probably an issue any other guard dog.
Lastly, I would suggest finding a good shelter or rescue group to work with. There are lots of good dogs that need good homes. I believe there is benefit from being able to see how the adolescent or adult dog behaves. When you buy a puppy, its hard to judge how they act latter in life, unless you can see the parents. Rescue groups will often have lots of great info on the difficulties of living with a particular breed, so check them out. Their list of requirements will give you a good idea of the issues.
Jim