We have a Border Collie, PJ, now 5 months old and she was raised with the chickens. She'll soon learn to "herd" the chickens into the coop at night. We also have a 1 year-old Yellow Lab, Tico, a 1 year-old Rhodisian Ridgeback, Holly, and a 10 year-old Cairn Terrier, Ariel. PJ already "herds" soccer balls, baseballs, footballs, kids, the other dogs, etc, etc.
Holly (100+ pounds of muscle and bone) is the protector and could shred a coyote with one bite. Unfortunately, she also loves to chase chickens and guineas. Tico (75 pounds of muscle and goofyness) is a true retriever, unintentionally killing two birds that wandered into his territory. Like a good bird-dog, he brought them directly to me!
The only predator we have are hawks. One was even bold enough to land in a tree directly above the coop. I had to fling sticks at it to get rid of it. Once PJ is a little older/bigger, she'll camp in the chicken run and will be able to handle predatory birds.
Coyotes, raccoons, feral cats, whatever...nothing gets close to our fences. Holly and Tico are far too intimidating to predators, but they are gentle giants with all of the kids.