If you are looking for a livestock guardian dog, I think you are looking for a Great Pyrenees.
In the Pyrenees mountains, the large white Great Pyrs guarded the flocks, and the little Berger des Pyrenees, called here Pyrenean Shepherds or "Pyr Sheps" for short, herded the flocks.
I am a Pyrenean Shepherd breeder and think they're a terrific breed, but they do not live with the livestock and watch over them, they involve themselves in a nosy and bossy way with all of the activities of their humans. They have good protective instincts and are excellent watch dogs and notice absolutely everything, as many herding breeds do, but their small size would not be effective against large predators. Several Pyr Shep owners have chickens as well, and their dogs are good with them, because this is a highly trainable, intuitive breed.
So...depends on what you are looking for! For herding, companionship, and absolutely for dogsports like agility, superb! Mine are great farm dogs, help with every chore, and make themselves useful in many ways, but aren't effective against any predator that isn't driven away by barking.
My dogs are related to many of the ones in those photos from the AKC site..and you can see more of them on my website
www.madcap.name.
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Madcap Pyr Sheps and Irish water spaniels, and a retired border collie
Clun Forest and Shetland sheep
Lipizzan horses