CBC had a documentary about Pet Stores in Canada. You can watch it online here:
How Not to Buy a Puppy | CBC News: Marketplace
It is very insightful, so please watch this!
Also on their website they published more info:
"The Hunte Corporation buys and sells up to 90,000 puppies a year. Dogs are purchased from breeders throughout the U.S. and brought to its 10,000 square facility in Missouri. Once there, the puppies are vaccinated, examined by vets, prepared for sale, and then trucked out to pet stores across the U.S. and Canada" (CBC)
You can read the whole article here:
The Pet Store Supply Chain | CBC News: Marketplace
Hope this helps!