A breed registry, also known as a herdbook, studbook or register, in animal husbandry and the hobby of animal fancy, is an official list of animals within a specific breed whose parents are known. Animals are usually registered by their breeders while they are young. The terms studbook and register are also used to refer to lists of male animals "standing at stud", that is, those animals actively breeding, as opposed to every known specimen of that breed. Such registries usually issue certificates for each recorded animal, called a pedigree, pedigreed animal documentation, or most commonly, an animal's "papers". Registration papers may consist of a simple certificate or a listing of ancestors in the animal's background, sometimes with a chart showing the lineage. Types of registries There are breed registries and breed clubs for several species of animal, such as dogs, horses, cows and cats. The US Association of Zoos and Aquariums (AZA) also maintains stud books for captive species on display ranging from aardvarks to zebras. Kennel clubs always maintain registries, either directly or through affiliated dog breed clubs. Some multi-breed clubs also maintain registries, as do non-affiliated breed clubs, and there are a few registries that are maintained by other private entities such as insurance agencies; an example of this in the United States is the Field Dog Stud Book. Working dog organizations also maintain registries. There are also entities that refer to themselves as registries, but that are thinly veiled marketing devices for vendors of puppies and adult dogs, as well as a means of collecting registration fees from novice dog owners unfamiliar with reputable registries and breed clubs. Although these entities generally focus on dogs, particularly in relationship to the puppy mill industry, some are marketed as cat registries. At least one group claims to register wild species (held by private individuals rather than by legitimate zoological parks, which use the AZA). Horse breeding also has such problematic registries, particularly for certain color breeds. While many color breeds are legitimate, some "registries" are primarily a marketing tool for poor quality animals that are not accepted for registration by more mainstream organizations. Other "registries" are marketing attempts to create new horse breeds, usually by breeders using crossbreeding to create a new type, but the animals are not yet breeding true. Many such questionable registries are incorporated as for-profit commercial businesses, in contrast to the formal not-for-profit status