*2.3.1.4 Disadvantages of individual selection*


It is concluded that the individual selection is based on individual's phenotype (appearance) and performance. Individuals are selected solely in accordance with their own phenotypic values. This is the simplest and yields more rapid response. It is the most commonly used method for selective improvement of livestock. Undoubtedly, most of the progress in livestock improvement can be credited to individual selection. Traits such as body type, growth rate, fleece production and other of similar nature can be evaluated directly from the performance of the individual animal, if suitable performance records are being kept; such evaluations are usually available by the time initial selection of breeding stock has to be made. In contrast, only a few can be progeny tested.

#### *2.3.2 Pedigree selection*

When the genetic worth or breeding value of animals is determined based on the performance of their ancestors or pedigree information is called as pedigree selection. Pedigree may be a record of an individual's ancestors associated with it through its parents. Therefore, the selection is based on the information of the ancestors of individuals that are related to it. Performance records from ancestors can provide useful information about the potential genetic worth or the breeding value of the individuals in question. This will give useful information before the animal is old. An estimate of calf's potential milk yield could be determined based on the milk yield of its mother until such time as the calf is grown up and can be milked. When adequate information on the merit of the individual is not available, then attention is given on pedigree information for selection of individual. From the selection point of view, knowledge of the different economic traits of the ancestors is essential [17].

It's usual to expect offspring of outstanding parents to be of superior genetic value than the mean of the individuals of the herd. Each parent transmits only sample halves of its genes to every offspring and just one quarter of genes from each grandparent. So, parents never provide the maximum amount of information about the breeding value of a single individual as individual's performance itself would produce. Unless the performance of the ancestor is well known, selection based on pedigree is meaningless. Distant ancestors of an individual give even less genetic information about the individual's breeding value especially for production traits. The pedigree is often classified into two as direct and collateral [2]. Collateral means those descended from same ancestors.

Selecting a cow based on the performance of its great grandparent is as good as random selection because the relationship is (0.5)2 = 0.125, i.e., only 1/8th of the superiority can be expected in the progenies. It will not do much good to go beyond three generations into pedigree due to the halving process of the chromosomes in each generation [9].

When the pedigree data provides information on the phenotypic and genotypic merit of the ancestors then it is called performance pedigrees. If the selection differential for the ancestor could be presented in the pedigree or if the performance record of the ancestor could be expressed as a percentage of the average contemporaries (Trait ratio), the ancestor's records would be of greater predictive value [9, 10].

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

#### *2.3.2.1 Degree of relationship*

If ancestors are more closely related to the individual (Parent: <sup>1</sup>*=*2, Grandparent: 1*=*<sup>4</sup> and Great grandparent: <sup>1</sup>*=*8) should receive most emphasis in pedigree assessment [16].

In pedigree selection, the PBV [3] of an individual is estimated on the basis of the performance of his ancestors.

$$\mathbf{PBV} = \overline{\mathbf{P\_c}} + \mathbf{b\_{AP}} \left(\overline{\mathbf{P\_i}} - \overline{\mathbf{P\_c}}\right)$$

Where, P is population mean, bAP is regression of additive genetic value or breeding value on phenotypic value, Pi is phenotypic average of individual, Pc is average phenotypic value of individual contemporaries,

**Figure 3.** *Schematic of pedigree selection [5].*

*Basic Animal Breeding Methods DOI: http://dx.doi.org/10.5772/intechopen.104136*

The selection criteria based on the ancestor's performance is called as the pedigree selection. For pedigree selection, more recent ancestors consider rather than distant.

### *2.3.2.2 Difficulties in pedigree selection*


The accuracy of pedigree selection when only single information is available for ancestor has been summarized in **Table 1**.

**Table 1** summarizes the accuracy of pedigree selection when only single information is available for ancestor (n = 1) [3]. The accuracy of selection based on individuals own record increases, when ancestors' information (parents and grandparents) is combined with an individual's own records.

When information of more than one ancestor are available the accuracy of selection increases, which is described in **Table 2**.

**Table 2** summarizes the accuracy of pedigree selection when information of more than one ancestor (n > 1) [3] is available. This increases the accuracy of selection. The pedigree selection is basically only useful to select the individual before its own records is available.

#### *2.3.2.3 Merits*



One grand parent 0.25 h2 0.25 h

• It is useful when two individuals have similar performance.

#### **Table 1.**

*Accuracy of selection (n > 1) [3].*


**Table 2.** *Accuracy of selection (n = 1) [3].*

