1. Inbreeding: Inbreeding refers to the mating of more closely related individuals within the same breed for 4- 6 generations.
  2. Out Crossing: This is the practice of mating of animals within the same breed, but having no common ancestors on either side of their pedigree up to 4-6 generations.
  3. Cross-breeding: In this method, superior males of one breed are mated with superior females of another breed.
  4. Interspecific Hybridisation: In this method, male and female animals of two different related species are mated. In some cases, the progeny may combine desirable features of both the parents, and may be of considerable economic value, e.g., the mule.