Inbreeding refers to the mating of more closely related animals of the same breed for 4-6 generations. Inbreeding involves the following steps 1) first the superior females ( cow) and superior males( bull) of the same breed are identified. Superior cow is the one that produces more milk per lactation. Superior bull is the one that is strong and has more vigour. 2) superior cows and superior bulls are mated to get the first progeny. 3) the progeny is evaluated and from them, the superior cows and superior bulls are identified for further mating. inbreeding increases homozygosity . It exposes harmful recessive genes which are eliminated by selection. Selective inbreeding helps in the accumulation of superior genes in a breed and elimination of undesirable genes. Inbreeding increases the productivity but continued inbreeding reduces fertility and leads to inbreeding depression. To overcome the inbreeding depression after a few generations the selected animals of the population are bred with the unrelated animals of the same breed or of a different breed. out breeding refers to the breeding of the unrelated animals. It could be out crossing - the practice of mating of animals within the same breed but having no common ancestor on either side of their pedigree for 4-5 generations- , b) cross breeding - superior male of one breed is mated with superior female of another breed , c) interspecific hybridisation- mating of male and female animals belonging to two different species.