Editing Selective breeding (section)

==Animal breeding==
{{Main|Animal breeding}}

Animals with homogeneous appearance, behavior, and other characteristics are known as particular breeds or pure breeds, and they are bred through [[culling]] animals with particular traits and selecting for further breeding those with other traits. [[Purebred]] animals belong to a single, recognizable breed, and purebreds with recorded lineage are called [[Pedigree chart|pedigree]]d. [[Crossbreed]]s are a mix of two purebreds, whereas [[mixed breed]]s are a mix of several breeds, often unknown. Animal breeding begins with breeding stock, 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 stock for a certain purpose, 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, to breed chickens, a breeder typically intends to receive eggs, meat, and new, young birds for further reproduction. Thus, the breeder has to study different breeds and types of chickens and analyze what can be expected from a certain set of characteristics before he or she starts breeding them. Therefore, when purchasing initial breeding stock, the breeder seeks a group of birds that will most closely fit the purpose intended.

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 superior in certain respects to the original base stock. Such animals can be recorded with a [[breed registry]], the organization that maintains [[Pedigree chart|pedigree]]s and/or [[stud book]]s. However, single-trait breeding, breeding for only one trait over all others, can be problematic.<ref name="grandin69">{{cite book|title= Animals in Translation|last= Grandin|first= Temple|author-link= Temple Grandin|author2= Johnson, Catherine|year= 2005|publisher= Scribner|location= New York, New York|isbn= 978-0-7432-4769-6|pages= [https://archive.org/details/animalsintransla00gran/page/69 69–71]|url-access= registration|url= https://archive.org/details/animalsintransla00gran/page/69}}</ref> In one case mentioned by the animal behaviorist [[Temple Grandin]], [[rooster]]s bred for fast growth or heavy muscles did not know how to perform typical rooster courtship dances, which alienated the roosters from hens and led the roosters to kill the hens after mating with them.<ref name="grandin69"/> A Soviet attempt to breed lab rats with higher intelligence led to cases of neurosis severe enough to make the animals incapable of any problem solving unless drugs like [[phenazepam]] were used.<ref>{{Cite web |url=http://www.znanie-sila.ru/golden/issue2print_9.html |title=Жили-были крысы |access-date=9 August 2014 |archive-url=https://archive.today/20140809185752/http://www.znanie-sila.ru/golden/issue2print_9.html |archive-date=9 August 2014 |url-status=live |df=dmy-all }}</ref>

The observable phenomenon of [[hybrid vigor]] stands in contrast to the notion of breed purity. However, on the other hand, indiscriminate breeding of crossbred or [[Hybrid (biology)|hybrid]] animals may also result in degradation of quality. Studies in [[evolutionary physiology]], [[behavioral genetics]], and other areas of organismal biology have also made use of deliberate selective breeding, though longer [[generation time]]s and greater difficulty in breeding can make these projects challenging in such [[vertebrate]]s as [[house mice]].<ref name="Swallow">{{cite journal | last1 = Swallow | first1 = JG | author-link2 = Theodore Garland Jr. | last2 = Garland | first2 = T. Jr. | year = 2005 | title = Selection experiments as a tool in evolutionary and comparative physiology: insights into complex traits—an introduction to the symposium | url = http://biology.ucr.edu/people/faculty/Garland/SwalGa05.pdf | journal = Integr Comp Biol | volume = 45 | issue = 3| pages = 387–390 | doi=10.1093/icb/45.3.387| pmid = 21676784 | s2cid = 2305227 | doi-access = free }}</ref><ref name="Garland">[[Theodore Garland Jr.|Garland]], T. Jr. (2003). Selection experiments: an under-utilized tool in biomechanics and organismal biology. Ch. 3, ''Vertebrate Biomechanics and Evolution'' ed. Bels VL, Gasc JP, Casinos A. [http://www.biology.ucr.edu/people/faculty/Garland/Garland_2003.pdf PDF]</ref><ref name="Garland_and_Rose">[[Theodore Garland Jr.|Garland]], T. Jr., Rose MR, eds. (2009). [http://www.ucpress.edu/books/pages/10604.php ''Experimental Evolution: Concepts, Methods, and Applications of Selection Experiments''.] [[University of California Press]], Berkeley, California.</ref>