Selection SELECTION

SELECTION

 The process that determines which individuals become parents.

Selection

Natural Selection Artificial Selection

The effects of selection on animal breeding

 Increase in the frequencies of genes that increase yields

 Increase in the number of highly productive individuals

 Increase in posibility of obtaining new genotypes

 Effect of selection on genetic variance and phenotypic variance.

 Increase in the frequencies of genes that increase yields

 Increase in the number of highly productive individuals

 Increase in posibility of obtaining new genotypes

 Effect of selection on genetic variance and

phenotypic variance.

O

Y

P

P G  

Herd which selection

made

P

P ^Y

Chosen group

P S

New generation

G = S h

S = P

- P

Genetic Gain

Selection differential

Genetic Gain

P

Genetic Gain

Parent Generation

Filial Generation S

G

Unchosen animals

Chosen animals

Selected animals for breeding

h 2

2 S

G S ^E  ^D .

2 

.h S

2 .h G S

2 D

2

E 



Genetic Gain

G = S h

F F

M M

G = i σ _p h ²

σ_p : Phenotypic standart deviation h² : Heritability

G = S h ²

P

P

σ

σ

G ^{Sh 2}

 _h ²

σ S σ

G

P P



Predicting of Genetic Gain

The values of selection intensities for expected truncation selection Proportion saved

(%)

Selection intensity

(i)

Proportion saved (%)

Selection intensity 0.90 (i)

0.85 0.80 0.75 0.70 0.65 0.60 0.55 0.50 0.45 0.40 0.35

0.195 0.274 0.350 0.424 0.497 0.570 0.644 0.720 0.789 0.880 0.966 1.059

0.30 0.25 0.20 0.15 0.10 0.08 0.06 0.05 0.04 0.03 0.02 0.01

1.159 1.272 1.399 1.555 1.753 1.859 1.985 2.064 2.152 2.267 2.420 2.670

Selection Intensity

Factors affecting genetic gain

1. Selection differential

Calculation of generation interval

2. Selection intensity 3. Heritability

4. Generation interval