There are three main approaches to selective breeding:Outcrossing, Linebreeding, and Inbreeding. Outcrossing Mating two animals that are unrelated for at least 4 to 6 generations back is called an outcross. This method works best when the genetic variation for a trait is high. When dominant genes are the desirable ones, outcrossing works perfectly well. One of the best advantages of outcrossing is that it hides detrimental traits by keeping them recessive. Outcrossing improves fitness traits such as reproductive ability, milk production, kid survivability and longevity. Linebreeding Linebreeding involves mating related animals like half-brother/half-sister, cousins, aunt/nephew, and other more distant relationships. This is usually done to capitalise on a common outstanding ancestor who appears in recent generations of the pedigree. There is a higher degree of uniformity with linebreeding than in outcrossing, and a reduced possibility of harmful genetic defects than inbreeding. Inbreeding This breeding method involved mating directly related animals, like mother/son, father/daughter, and full brother/full sister (full siblings). This method is used generally to create uniformity and prepotency (the ability of this process to continue) and to force out latent weaknesses from the gene pool. However, recessive genes are more of a factor than dominant genes in genetic faults, so there is a high risk producing kids with problems. Inbreeding reduces the pool of available genes and can cause some lines to become extinct. Fitness traits are especially at risk with this breeding scheme.