Imagine a
hundred or more
female dogs kept in
cages, serving one
purpose - making as many
puppies as possible.
These dogs are never let out of the cages, sick with disease, and given rotten food. The puppies are sorted through for ones that are worth selling and the others are disposed of in some manner.
It's done. It's not that uncommon. And beware when you buy a puppy from somewhere. If you are looking for a dog, go to the humane society or the equivalent. If you absolutely must have a dog of a certain breed, perhaps for doing dog shows, then visit the breeder, inspect the conditions, make sure where the puppy comes from. Don't do anything that would encourage a puppy mill.