There approximately 8,000-10,000 puppy mills in the U.S. and this would include many businesses that call themselves breeders such as "backyard breeders", people who purposely allow their dog to get pregnant in hopes of selling puppies through their local paper or online. Pet stores that sell puppies are the number one reason that so many puppy mills exists today. Convince each and every pet store to stop selling puppies and the mills will go out of business. The most successful way to accomplish this is by organizing rallies and peaceful demonstrations outside of pet stores that sell puppies.
The tragedy of puppy mills is that they don't care about the animals more than a commodity to be sold. Most of these animals live in crammed cages with no room to move, in complete and utter squalor. Many puppies are sick and never given true health exams, necessary vaccines or proper health care. The puppies are always taken way too early from their mothers, so they're denied the basic social skills they need to behave well in the home, thus, resulting in many dogs later being abandoned at the shelter. After a female dog's fertility wanes, she is often killed, abandoned or sent to another mill that will attempt make her produce one more litter. Puppy mills and backyard breeders are the number one reason we have an overpopulation of dogs in this country...that and a lack of spaying and neutering.
Responsible breeders have a limited number of litters per year, they care for their animals like their own and help to keep bloodlines pure. However, people need to do their homework if they want to buy a pure breed puppy from a breeder. They need to make sure that the breeder is licensed by their city and state, has a good reputation, no BBB complaints, no law suits, valid customer testimonials, a health certificate from a reputable vet and no signs of illness with their puppies. If you go to visit your prospective puppy from a breeder, be wary of the following:
Bad odor/unhealthy conditions in kennel
Breeder unwilling to allow you to see the puppy's mother and father
Puppies with weepy eyes and overall lethargy
A puppy that shows no interest in interacting with people
A skinny puppy
A limping puppy
Better yet, there are many pure breed puppies and young adult dogs that are orphaned for one reason or another and there are plenty of pure breed rescues that you can visit to give one or more of them a forever home. National Puppy Day encourages you to always consider adoption first.