I got the info Here -
http://www.doggiesparadise.com/puppymills.shtml
The puppies from these puppy mills are
called "purebreds" but often assume little similarity to their breed standard.
Decisions about which male to use with which female are based on profitability, leaving genetic issues for the unsuspecting puppy buyers to worry about later.
Unsafe breeding practices incline puppy mill dogs to inherited disorders like immune system deficiency, hip dysplasia, demodectic mange, seizures, yeast infections, or aggressive dog behavior.
Puppy mills over breed indiscriminately, as often as they can with as little cash output as possible. Puppy mills owners do not care about the future health of the puppies or the ruin they will cause in the lives of the people who buy them.
Furthermore,
registration papers do not guarantee proper breeding conditions, health, quality, or claims to lineage of the puppy.
Lovely business isn't it.