Simultaneous selection for many traits can be applied based on individuals own performance by adopting any of the procedure of selection. One may wish to adopt tandem selection or ICL methods or one may evaluate the individuals on the value for each of the traits selected for and then sum of these values to give a total value for all the traits. The animal with the highest score is then selected. These procedure are known as methods of selection.

1. METHODS OF SELECTION
Presented by: Dr. Jayesh Vyas

2. Methods of Selection
1.Single trait
2.Multiple trait selection
 Success of rising animal depends on
improvement in more than one trait.
 Single trait selection can have unexpected and
undesirable consequence due to genetic
correlation and environment response.

3. • Methods of selection-
Simultaneous selection for many traits can be
applied based on individuals own performance by
adopting any of the procedure of selection.
One may wish to adopt tandem selection or ICL
methods or one may evaluate the individuals on the
value for each of the traits selected for and then sum
of these values to give a total value for all the traits.
The animal with the highest score is then selected.
These procedure are known as methods of selection

4. 1.Tandem Selection
In this method of individual selection the
selection is practiced for one trait only at a time until
a satisfactory improvement is achieved .
The efficiency of this selection depends on the
genetic correlation among the traits under selection.
Limitations –
1. This method is less efficient than other methods.
2. It requires more time for improvement in all the traits

5. 2.Independed culling levels (ICL)
This method of individual selection
involves selection for two or more traits at a
time.
A minimum standard for each trait is fixed and
every animal to be selected must meet the
minimum standard fixed for any one of the trait
will be rejected, irrespective of the fact that
how good the animal was in other trait.

6. • Advantages of ICL
1.Selection for more than one trait.
2. Culling at early stage.
Disadvantage of ICL
1.No compensations for other traits
2. Culling level- tedious job to decide CL
3.More emphasis to early expressed traits
4. Selection intensity

7. • ICL method of selection is used in selection of cattle
for show purpose.
• The animal is selected with excellence of type,
colour and conformation traits ignoring its
performance for economic traits.
 Selection intensity under ICL:-
. The selection intensity is decreased by selection for
more than one trait.
. The genetic correlations among traits also influences
the selection intensity.
selection intensity= 1/√n
n= no traits which are equally important and
independent

8. • 3Total score or selection index
.In this method of mass selection , the selection
is practiced for several traits simultaneously.
But this method differ from ICL in that
.The culling level are flexible. .
.Each trait is weighted by a scores for
individual traits are summed to a total score
(index value) for each animal.
.Superiority in some trait can make up
deficiency in other, unlike ICL which discards
an animal; failing to qualify in one trait
regardless of its superiority in other trait.

9.  Efficiency of S.I. over other methods
of selection
S.I. is a more efficient method of selection
than others
(1) It allows the individuals which are superior in
some traits to be selected regardless of their
inferiority in other traits .
(2)The advantage of index method increase with
the no. of trait, thus it requires less time to bring
about an overall improvement

10.  Use of discriminate function to
construct selection index
• Selection index method involves the technique
of discriminate function originally developed by
Fisher (1936) and used by Smith (1936).
The index will take the form as:
I=b1x1+b2x2+.........+bnxn
Where, xi =represent the phenotypic value for
the different traits
bi=the weighting factors given to each
the trait.

11.  Genetic basis of selection index:-
The genetic worth of an individual is expressed
as
H=a1G1+a2G2+a3G3+.........anGn
where,
G1, G2.....Gn are the genotypic value of
individual character.
a1, a2..........an to their relative economic
importance.
H=The overall net genetic worth for several
traits

12. .The phenotype of an individual based on the
phenotype performance of various traits is
defined as:
I=b1x1+b2x2+.........+bnxn
.Where
X1,X2....Xn=the phenotypic value of the trait.
b1, b2.....bn=the coefficient of each trait.
.These coefficient are to be estimated in such a
way that the correlation b/w H and I become
maximum.

13. Information required for construction
of selection index-
• The construction of a selection index requires:-
1.The economic value of each of the trait.
2.The genetic and phenotypic variance of all
traits.
3.The genotypic and phenotypic co-variance
among traits.

14. 1.Estimation of economic value:-
. It is important to know the method of
estimating the relative economic value of the
trait, by taking the example of cattle.
. The most important economic traits are age at
first calving (AFC), Milk yield, lactation length,
peak yield, and milk yield per day of calving
interval etc.
. In order to bring about similarity among different
traits, the economic value of a standard unit of
each trait is considered.

15. Construction of selection index:-
selection index is considered in following steps-
1.Estimation of genetic and economic parameters-
The following genetic and economic parameters of the
traits included in selection for improvement are
estimated:-
I. The economic value of for all the traits based on price
data and profit.
II. The genetic and phenotypic variance of all traits.
III. The genotypic and phenotypic co-variance among
traits.

16. 2.Estimation of partial regression
coefficients:-
The selection index (I)is:
I=∑b i=b1x1+b2x2+.........+bnxn
• Where
Xi=the phenotypic value of the trait.
bi=are the partial regression coefficient
of each trait.

17. • The regression coefficients are estimated by setting and
solving the normal simultaneous equations for n traits
under selection as follows:-
1 . bi Vpi+b2 CovP12+...+bn Cov
P1n=a1 VA1+a2 Cov A12+....+an Cov A1n .
2. bi
Cov P21+b2 Vp2+...+bn Cov
P2n=a1CovA21+a2 VA2+....+an CovA2n
3. bi Cov Pn1+b2 Cov Pn2+...+bn Vpn
=a1CovAn1+a2CovAn2+....+bn Van
.

18. • The above equations are solved for bi values.
The variances and covariance and economic
values are first determined and put into the
above equations to solve for bi values.
Selection index:-
The selection index I=b1x1+b2x2+.........+bnxn
the bi and xi values are put up in the index to
obtain the index values for each animal and the
animals with top highest index values are
selected.

19.  Practical problems in constructing selection
index:-
1.The information required is not available or
accurate enough.
2.The relative economic importance of traits varies
from time to time and in different locality.
3.It requires information of price and cost of
production, of the traits, but sometime the
economic values changes due to change in market
demand.
4.To find the genetic and phenotypic parameters is
not an easy job when the no of traits exceeds three
or more.

20.  Comparative efficiency of different
methods of selection:-
• Hazel and Lush (1942) compared the efficiency
of these three methods in terms of genetic gain,
assuming that traits under selection were
independent, and had equal heritability,
economic weight and variance.
(1)In tandem method the selection may be for
unimportant character in the beginning of first
few generations and selection for more
important character may be for a brief period.

21. (2)In ICL method ,the culling levels may be set too
high for one trait and too low for other.
(3)In selection index method there may be
mistake in estimating genetic parameters and
economic value.
. Lastly, the selection progress is also affected by
animal health which affects p (proportion of
selected individuals),and also by the breeders
ability to record the observations properly.
.Thus ,Hazel and Lush (1942) concluded that index
method was most superior and tandem
selection least, whereas the efficiency of ICL
method was intermediate.

22. • Two trait selection index:-
When two trait for construction of selection
index are used then the genetic worth of an
individual can be expressed as
H=a1G1+a2G2
where-
G1,G2 = genotypic values of individual character
a1a2= refer as their relative economic
importance.

23. • The phenotype of an individual based on the
phenotypic performance is as:
I=b1X1+b2X2
Where-
X1X2 are the phenotypic values of the traits
1and 2
b1b2 are coefficient of each trait.
These coefficient are to be estimated in such a way
that the correlation b/w H and I become
maximum.

24. Thank You