Humans have maintained populations of useful animals around their places of habitat since pre-historic times. They have intentionally fed dogs considered useful, while neglecting or killing others, thereby establishing a relationship between humans and certain types of dog over thousands of years. Over these millennia, domesticated dogs have developed into distinct types, or groups, such as livestock guardian dogs, hunting dogs, and sighthounds.
To maintain these distinctions, humans have intentionally mated dogs with certain characteristics to encourage those characteristics in the offspring. Through this process, hundreds of dog breeds have been developed. Initially, the ownership of working and, later, purebred dogs, was a privilege of the wealthy. Nowadays, many people can afford to buy a dog. Some breeders chose to breed purebred dogs, while some prefer the birth of a litter of puppies to a dog registry, such as kennel club to record it in stud books such as those kept by the AKC (American Kennel Club).
Such registries maintain records of dogs’ lineage and are usually affiliated with kennel clubs. Maintaining correct data is important for purebred dog breeding. Access to records allows a breeder to analyze the pedigrees and anticipate traits and behaviors. Requirements for the breeding of registered purebreds vary between breeds, countries, kennel clubs and registries.
Breeders have to abide the rules of the specific organization to participate in its breed maintenance and development programs. The rules may apply to the health of the dogs, such as joint x-rays, hip certifications, and eye examinations; to working qualities, such as passing a special test or achieving at a trial; to general conformation, such as evaluation of a dog by a breed expert. However, many registries, particularly those in North America, are not policing agencies that exclude dogs of poor quality or health. Their main function is simply to register puppies born of parents who are themselves registered.
The term ‘backyard breeders’ is commonly used in Canada and the U.S. to describe a breeder with a lack of knowledge and experience; while the term ‘puppy mills’ or ‘puppy farms’ refers to businesses that mass produce puppies of different breeds. Animal rights activists claim that breeding dogs to sell them is unethical, criticizing breeders who they believe are more concerned with profit than the animals’ welfare. Critics cite breed registries for encouraging the inbreeding of dogs, thereby contributing to a proliferation of genetic disorders.
Some dogs have certain inheritable characteristics that can develop into a disability or disease. Excessive wear of hip joint or bone, known as hip dysplasia is one such condition. As well, some eye abnormalities, heart conditions, deafness, are proven to be inherited. There have been extensive studies of these conditions,commonly sponsored by breed clubs and dog registries, while breed clubs provide information of common genetic defects for according breed. As well, special organizations, such as Orthopedic Foundation for Animals, collect data and provide it to breeders, as well as to the general public.
Some registries, such as American Kennel Club include records of absence of certain genetic defects, known as certification, into dog’s individual records. For example, the German Shepherd National Breed Club in Germany is a registry that recognizes that hip dysplasia is a genetic defect for the dogs of this breed. Accordingly, it requires all dogs to pass evaluation for absence of Hip Dysplasia to register their progeny, and records the results in individual dog’s pedigrees.