Why is inbreeding carried out in animal husbandry?

Increases homozygosity

Inbreeding is mating of closely related animals of the same breed. Inbreeding increases homozygosity, i.e., state of possessing two identical alleles, one inherited from each parent.

It is necessary if we want to evolve a pureline in any animal. Inbreeding exposes harmful recessive genes that are eliminated by selection. It also helps in accumulation of superior genes and elimination of less desirable genes.

Outbreeding is mating of unrelated animals. Generally, outbreeding increases vigour and improves quality of the breed. It also increases heterozygosity.