Livestock species are divided into genetic groups called breeds. Unfortunately, a clear definition of the term breed is difficult to find. Breed might be defined as a group of animals with similar physical characteristics (such as color, horns, body type, etc). However, there are breeds that contain wide variation in such traits, while some breeds may share many characteristics. There is general agreement that the concept of a breed denotes common ancestry. However, some breed organizations choose to allow entry of animals from other breeds. An early observation was made about the definition of breed:[1] ''A breed is a group of domestic animals, termed such by common consent of the breeders, a term which arose among breeders of livestock, created one might say for their own use, and no one is warranted in assigning to this word a scientific definition and in calling the breeders wrong when they deviated from the formulated definition. It is their word and the breeders' common usage is what we must accept as the correct definition.'' A breed has also been described as something that arises more rapidly than normal evolutionary processes would allow but more slowly than would be true in the laboratory.1-2-1 Some breeds arise almost entirely through natural forces, whereas others are developed by human managers in a highly directed fashion. The total number of recognized breeds is probably in excess of 1000 worldwide, although some are just national derivatives of the same breed.[3] Several hundred of these breeds are illustrated in the Breeds of Livestock website maintained by the Department of Animal Science at Oklahoma State University ( Numerous breeds have also been described in other venues.[4,5]

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