**3. Systems of breeding**

Systems of breeding can be classified into two major groups: Inbreeding and Out breeding [5, 22].

#### **3.1 Inbreeding**

Inbreeding is the mating of animals more closely related to each other than the average relationship with in the population concerned. The mated individual should have one or more common ancestors in their pedigree up to 4–6 generations. Inbreeding includes mating like parent-offspring, brother–sister. Inbreeding is classified into two types: close Inbreeding and line breeding [22].

Close inbreeding is mating between sibs or between parents and progeny to achieve inbred lines with a relatively high degree of homogeneity. Most of the time, we use the full sib mating method. The same effect can be achieved by consistently back crossing the progeny to the younger parents. Line breeding is a milder form of close inbreeding is in which the relationships of mated individual is kept as close as possible to some ancestor. As a general rule sire is not mated to its daughters but half sib mating is made among the offspring of the particular sire. Line breeding was used extensively in the past in development of British breeds of cattle such as Angus, Hereford and Shorthorn [3]. Line breeding should be practiced in purebred populations of the high degree of excellence, after identifying outstanding individuals and it can be advocated to form a new breeds.

Inbreeding is that it makes more pairs of genes in the population homozygous irrespective of the type of gene action involved. Inbreeding does not increase the number of recessive alleles in a population but merely brings to light through increased homozygosity. When the animals are homozygous for several traits, the regularity of inheritance is assured (i.e., it fixes the characteristics). Inbreeding reduces vigor or it results an inbreeding depression.

Despite certain obvious disadvantages of inbreeding, there are certain instances where it may be used as the advantage of livestock production. It is used to maintain genetic purity and thereby to increase prepotency. It is also used to develop inbred lines and also to eliminate undesirable recessives from the population. When a sire is mated to at least twenty of its daughters and does not produce any recessive characters in the offspring, it may conclude that the sire is not heterozygous for recessive characters.

Inbreeding is to be practised only when the herd is better than the average, i.e., when the frequency of desirable genes is more, herd has an outstanding sire, the breeder knows the merits and demerits of inbreeding and the herd is not maintained for commercial purpose.

#### **3.2 Out breeding**

Out breeding is the mating of animals that are less closely related to each other than the average of the population. Its general, effects are the opposite of those of inbreeding. Out breeding increases the heterozygosity of the individual. The maximum practical usefulness of out breeding systems is the production of animals for market. Out breeding is a form breeding where the mates are chosen based on not being related. The following type of out breeding is used in animal breeding [3, 6].

#### *3.2.1 Selective breeding*

The selective breeding is used to maintain the purity of the breed along with their improvement. **Figure 4** describes the brief information for genetic improvement of indigenous cattle breeds by selective breeding is shown below:

**Figure 3** is showing the different basis of selection which are commonly used to estimate the probable breeding for selection of animals for single trait.

#### **Figure 4.**

*Schematic of selective breeding [3, 5].*
