Animal breeding

Breeding stock is a group of animals used for the purpose of planned breeding. When individuals are looking to breed animals, they look for certain valuable traits in purebred animals, or may intend to use some type of crossbreeding to produce a new type of stock with different, and presumably superior abilities in a given area of endeavor. For example, when breeding swine for meat, the "breeding stock should be sound, fast growing, muscular, lean, and reproductively efficient." The "subjective selection of breeding stock" in horses has led to many horse breeds with particular performance traits. While breeding animals is common in an agricultural setting, it is also a common practice for the purpose of selling animals meant as pets, such as cats, dogs, horses, and birds, as well as less common animals, such as reptiles or some primates.

Mating animals of the same breed for maintaining such breed is referred to as purebred breeding. Opposite to the practice of mating animals of different breeds, purebred breeding aims to establish and maintain stable traits, that animals will pass to the next generation. By "breeding the best to the best", employing a certain degree of inbreeding, considerable culling, and selection for "superior" qualities, one could develop a bloodline or "breed" superior in certain respects to the original base stock.

Such animals can be recorded with a breed registry, the organisation that maintains pedigrees and/or stud books. The observable phenomenon of hybrid vigor stands in contrast to the notion of breed purity.

For laboratory purposes, organisms such as mice have been inbred to 100% pure lines, as offered for sale by the Jackson laboratory. But this is highly unusual and difficult to do for most organisms, in whose populations all individuals harbor recessive, deleterious gene variants (alleles).