Wow, what an ignorant statement. You do know that dogs, just like people and other animals, die, yes? It happens

These dogs are treated well--if they weren't they would not be able to perform. The dogs have value to their owners, and are not fodder for mistreatment.

What do you propose to do with dogs who are created to run? Put them in kennels? Keeping a dog locked up in a kennel or confined to a house is not kindness. Training and running is. Chaining dogs is no more cruel than caging them, and caging dogs is all the rage in dog training today. Are leashes cruel? Perhaps you would prefer that these dogs roam the wilderness without restraint, to be attacked and eaten by wolves or bears or stomped by moose?

Also, the dogs do interact with one another. How do you think kennels increase in size?