Pet shops and the internet are helping perpetuate a host of genetic disorders in dogs, according to animal welfare experts.
Inherited health problems in dogs can cause blindness, lameness, heart problems and cancer.
There are 500 recognised inherited disorders affecting 300 breeds of dogs, including the most popular: Labradors, German Shepherds and Golden Retrievers.
In the worst cases, owners end up facing hefty vet bills or must have their pets put down.
Bob Kerridge from the SPCA in Auckland would like pet shops to stop selling dogs. He says the shops may be innocently trading in animals which have health problems, as they're sourced from "back yard breeders".
Veterinary specialist and lecturer Andrew Worth of Massey University says the problem is exacerbated when there is a disconnect between between breeders and new owners, such as when a puppy is sold over the internet.