Principles of Animal Breeding: Selection and its Basis

 
ANIMAL GENETICS & BREEDING
UNIT – III
Principles of Animal Breeding
Theory
 
Selection and its Basis
 
Dr K G Mandal
Department of Animal Genetics & Breeding
Bihar Veterinary College, Patna
Bihar Animal Sciences University, Patna
 
Introduction to selection
 
Choosing of best individuals among the lot.
Objective of selection?
 
For further 
improvement
 in a particular field.
Various 
Fields
 are:
i.
Wining of medal in Olympic games & sports
ii.
Wining of Nobel Prize (Nobel laureate)
iii.
Literacy & Cultural events – singing, dancing (Mr. India & Miss
India)
iv.
Higher education – IIT, IIM, IISc, AIIMS, Science &
Technology, Vety. & Agri. Science etc.
v.
Service – Adm.(IAS), Engineer, Doctor, Professor, Scientist,
Judge, Officer, Army, School teacher etc.
 
Criteria of selection
 Or Basis of selection?
 
Individual 
merit
 only
Method of selection:
 
 
Competition
 
 
Competitive exam
 
 
Interview
 
 
Competitive exam & Interview both
 
 
Group discussion
 
 
Physical fitness
 
 
Medical test
Accuracy of selection
 – the factors which increase the
efficiency of selection – selection index or total score
 
Selection of farm animals
 
Definition:
 
1.
 According to 
Prof. I M Lerner
: 
selection is the non-
random differential reproduction of different genotypes.
i.
Differences in 
fertility
 among individuals in parent
generation
ii.
Differences in 
viability
 among the progeny
iii.
Choice
 of mated individuals
 
 
2.
 According to 
Prof. Jay L Lush
: 
selection is the
differential reproductive rates within the population whereby
some individuals tend to have more offspring than the others.
i.
All individuals are 
not allowed
 to be the 
parents.
ii.
Difference in fitness
 from individual to individual.
 
Types of selection
 
Natural Selection
Selection operates through 
natural forces
 like
fertility
 and 
viability
.
Nature selects individuals which are 
more adaptable
and more fit
 in a particular environment.
 
Artificial Selection
Selection operates through 
intervention of man
 (animal
breeder)
Superior individuals
 will be allowed to be the parents
for next generation.
Natural selection 
favours
 artificial selection.
 
Effect of Selection :
i.
There will be 
change
 of 
genotype frequency
 and 
gene frequency
.
ii.
It 
increases the frequency
 of 
desirable genes
iii.
It 
does not create
 
new genes
 in the population
iv.
As a result of selection there will be change of 
population mean.
 
Objective of selection:
i.
To 
increase the mean value
 of performance traits in
subsequent generations.
ii.
To 
maximize the response
 to selection.
iii.
To decide
 the minimum effective 
population size (Ne)
.
 
Criteria or Basis of Selection
 
Breeding value
 is the only 
criteria of selection.
Value associated with the genes carried by an individual is the B.V.
The 
sources of information
 based on which the 
breeding value
 of an
individual is estimated are called as the 
basis of selection
 or aids to
selection or 
criteria of selection
.
Breeding value
 
of an individual
 is estimated either from the 
phenotypic
value
 of the 
individual
 itself or from the 
phenotypic value
 of its
relatives.
Information from relatives
 is 
very important
 to 
estimate the breeding
value
 of an 
individual.
Because there are 
certain percentage of
 
genes
 which are 
common
between individual and its relatives
 due to 
common ancestry
.
 
 
Use of 
information from relatives
 is very  important to
estimate the breeding value
 of the individual under the
following conditions:
i.
When 
individual selection is not possible
.
a.
Sex-limited traits
 – milk production, egg production
b.
Traits can not be measured
 in living animals – slaughter traits
ii.
When 
selection
 is required at the 
earlier age
 but the 
trait
is expressed
 
later in life
.
iii.
When 
h
2
 of the trait under selection is 
low.
The breeding value so obtained is known as 
estimated
breeding value (EBV)
 or 
probable breeding value (PBV)
 or
predicted breeding value.
 
Basis of Selection
 
The 
sources of information
 based on which the 
breeding
value
 of an individual is estimated are called as the 
basis of
selection 
or
 
Principles of selection
 
or
 Criteria of selection.
 
1.
Individual Selection
2.
Pedigree selection
3.
Family selection
4.
Within family selection
5.
Sib selection
6.
Progeny testing
 
1. Individual Selection
 
Selection is made 
on the basis of own performance 
or 
own
phenotypic value
.
When 
breeding value
 of an individual is estimated based on
its 
own phenotypic value,
 then it is known as 
individual
selection.
Individual selection is also known as 
mass selection
 when
selected individuals are kept together 
en mass
 for mating.
 
Example: Drosophila and Tribolium
Conditions applied
 for individual selection:
 
(i) when 
traits are expressed in the individual 
and
 
(ii) when 
h2 of the trait is high
 
(iii) when 
mating records are maintained
 
Estimation of breeding value
 :
 
breeding value (BV)
 of an
individual is estimated from the 
phenotypic value
 of the
individual as a 
deviation from the population mean (
selection
differential
) times the h
2
 of the trait
 and known as 
Probable
Breeding Value
 (PBV).
 PBV = P + h
2
(Pi – P)
Where, P = Population mean, h
2
 = heritability
 
   P
i
 = phenotypic value of the individual
 
 
Accuracy of individual selection:
It depends on magnitude of 
r
AP
Correlation between breeding value and phenotypic value (
r
AP
 )
 is
equal to the 
square root of h
2
 (r
AP
 = h)
The 
accuracy
 of predicting the 
breeding value
 of an animal will be
increased
 with the 
increase in magnitude of h
2
.
Efforts must be made to get 
accurate estimation of h
2
 by reducing
the 
environmental variations,
 and by estimating h
2
 based on
repeated records of individual.
 
 
Limitation of individual selection:
1.
Cannot be applied for 
sex-limited traits
.
2.
Cannot be selected If the traits are expressed 
later in life
 or 
after
death of individual (
slaughter traits
)
3.
Traits with 
low h
2
 
is the limiting factor.
 
When h
2
 is low, the phenotypic value is the 
poor indicator of
breeding value
. Since, h
2
 = r
2
AP
 and accuracy of selection h = r
AP
.
 
Advantages of individual selection
:
1.
Information
 of the individuals are 
easily available
.
2.
It 
can be applied
 before 
progeny testing
3.
Used when 
pedigree information
 are 
not available
4.
Generation interval
 
is shorter
 in comparison to progeny testing
5.
It gives 
direct estimation of BV.
 Does not depends on relatives.
6.
It allows greater estimation of 
selection differential
 than the
progeny testing.
 
Aids to individual selection:
Individual selection will be more difficult when:
i.
Heritability of the trait is 
low to medium
ii.
Information of relatives are 
not available
When h
2
 of a trait is low, the 
repeated records
 of the same animal
 can
be used for estimation of breeding value.
Use of part records and genetic correlation among the traits will be
helpful when earlier selection is practiced for the traits expressed
later in life.
1.
Additional records
2.
Most probable producing ability (MPPA)
3.
Use of part records
 
3. 
Use of part records:
Genetic gain by use of part records, ∆G = b
AP
(X
Pi
 – X
P
)
 
where, b
AP
 = regression of breeding value on part records
  
Xpi = part record of individual animal
  
X
P
 = Mean part records of population
  
(X
Pi
 – X
P
) = Selection differential
 
2. Pedigree Selection
 
Selection of an individual based on performance of its
ancestors is known as 
pedigree selection.
Pedigree is the 
systematic list
 or 
records
 of 
ancestors
 of an
individual.
Ancestors are 
parents,
 
grand parents,
 
great grand parents
,
etc.
Pedigree having information on the 
economic traits
 of
ancestors is useful for 
selection
 of 
an individual.
Breeding value
 of an individual is 
estimated
 on the basis of
performance of ancestors.
 
Basis of pedigree selection:
An 
individual is related by 
50%
 with its parents
, 
25%
 with
grand parents,
 
12.5%
  with 
great grand parents
 and so on.
The relationship is 
reduced to half in each generation
 due to
halving nature of inheritance.
It is thus more important to 
consider 
recent ancestors
(parents) than the 
remote ancestors
 for pedigree selection.
Inclusion of more 
remote ancestors results
 only in 
marginal
gain.
Pedigree selection 
adds very little
 to the accuracy of
estimating  BV of an individual 
if information on individual
are available.
 
Significance of pedigree selection decreases when
information are available either on individual or its family
members (sibs & progeny).
 
Guide to the pedigree selection:
Degree of genetic relationship
more closely related
ancestors
 should be given 
more emphasis.
Heritability of the character
 – pedigree selection is more
accurate for characters of 
high h
2
.
Information should be available on ancestors.
 
Advantages of pedigree selection:
Allows selection at 
younger age
.
It is helpful in 
multistage selection.
It is useful for 
sex-limited traits
 and traits expressed 
later
in life
 or 
after death of animal
 (eg. 
slaughter traits
).
It is helpful when 
two individuals have similar performance
but one belongs to a better pedigree.
It is 
less costly
, as only compilation of pedigree is required.
 
Demerits of pedigree selection:
Characters with 
low h2 can not be improved
 to the level of
expectation.
Some pedigree gets 
undue emphasis and favoured
. Better
environment is provided to the favoured pedigree.
Pedigree selection provides 
no basis of selection
 among
individuals when 
descendants are from the same ancestors
.
 
 
Estimation of Breeding Value (BV):
The BV of an individual from pedigree records is estimated by
the 
selection differential 
of its relatives (P)
 taken  as a deviation
from their 
contemporary average (Pc)
 times the 
regression 
of
the genotype of the individual on the mean phenotypic value  of
the relatives (b
AP
) and added to the mean of contemporary group
as:
 
P.B.V
. = 
Pc + b
AP
(P – Pc)
The 
b
AP
 is taken as 
rh
2
 where r is the coefficient of relationship
between the individual and its relatives.
In 
estimating the PBV
 of an individual the record(s) of 
one
parent
 or 
both parents 
or 
parents and grand parents
 can be used.
The 
information on ancestors 
combined with individual’s own
record
 
increases the accuracy of selection.
 
Accuracy of pedigree selection:
The selection based on the 
performance of one parent
 
is half
 
as
effective (accurate) as
 that based on 
individual’s own
performance.
The information on records of 
both the parents
 
plus all the
 
four
grand parents 
gives 
lesser accuracy of selection
 which does not
exceed 0.71 than based on individual’s own record.
The information on records of 
ancestors (both the parents plus
all the four grand parents)
 
combined with individual’s own
performance
 gives 
little higher accuracy of selection
 than based
on 
individual’s own record
.
The 
accuracy of selection
 based on 
single parent
 
never exceed to
0.50.
 
3. Family selection
 
Information from 
collateral relatives
 may be used for
estimation the B.V. of an individual.
Among the collateral relatives, 
full-sibs
 and 
half-sibs
 are
more closely related
 to the individual.
Full-sibs and half-sibs constitute 
full-sib family
 and 
half-sib
family
 respectively.
Selection of an individual on the basis of 
family mean
 is
called 
family selection
 or 
sib selection
 depending upon
inclusion or exclusion of 
individual’s own performance
 in the
family mean.
Selection of an individual on the basis of family mean is
called family selection when 
individual’s own performance is
included
 in the estimation of 
family mean.
 
 
In 
family selection
 the 
criteria of selection
 is based on the
performance of sibs plus individual’s own record
.
Types – Full-sib family selection & half-sib family selection.
Family will be taken 
as a unit
 and 
depending upon 
family
mean
 the whole family will be 
selected or rejected.
If the family is selected, then the 
inferior individual
 of the
family should also be 
selected
.
If the family is rejected, the 
superior individual
 of the
family will also be 
rejected.
Family selection is practiced for the following traits for
which 
measurements of individual are not available:
i.
Traits with 
low heritability
 and 
high reproductive rate
litter
size
 
Sib selection: 
Selection of an individual on the basis of
family mean is called 
sib selection
 
when
 individual’s own
performance is not included in the estimation of family mean
.
An individual is selected on the basis of average
performance of sibs.
Average performance of sibs
 is the 
criteria of selection.
Depending upon types of sibs, it is two types – 
Full-sib
family selection
 and 
half-sib family selection.
 
 
Sib selection is practiced
 for improvement of the 
following
traits
 for which 
measurements of individual
 
are not
available
:
Traits with 
low heritability
 and 
high reproductive rate
litter size
Sex-limited traits
 – milk production, egg production
Traits can not be measured on the individual
slaughter
traits
 
Advantages of family selection:
It is 
suitable
 for traits with 
low heritability
 and 
high
reproductive rate
. Eg. 
Litter size
 in pig, 
egg production
.
It 
reduces generation interval.
It is an 
aid to individual selection
 because it is better to
select an individual from a superior family.
Limitation:
It leads to 
inbreeding
Full-sib family selection can only be applied in species with
high reproductive rate to get 
large family size
.
Family selection is costly
 since large number of families are
required to be maintained.
 
4. Progeny Testing
 
Selection of an individual based on it’s 
progeny performance
 is
known as progeny selection or progeny testing.
It is the 
most important basis of selection.
Mean phenotypic value
 of the progeny is taken as the deviation
from mean phenotypic value of contemporaries.
Each progeny inherits 
one-half of the genes
 from 
each parent
due to 
halving nature of inheritance.
This is taken as 
transmitting ability of the parent
.
Hence 
B.V. of the parent is twice the mean deviation of the
progeny from the population mean.
 
B.V. = 2(M – P)
Where, M = progeny mean, P = population mean
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Superiority of P. T. over other selection criteria:
Individual selection is not possible
 for traits of 
low h
2
, 
sex
limited traits
 and the traits expressed 
after death of individual
.
Pedigree selection
 is based on 
performance of dams
. Due to
halving nature of inheritance
 it is not possible to know that 
which
half (better or inferior) of dam’s genes
 is received by the
progeny.
Accuracy of sib selection 
is also 
low
 due to 
sampling nature of
inheritance.
In progeny testing, the 
performance of many progenies
 gives the
best and most reliable information
 about the 
genetic merit 
of
the 
individual (parent).
 
 
Precautions in Progeny Testing:
Adult 
females should be allotted randomly to all the sires under test
to avoid the effect of dam on progeny.
Different sire groups
 should be 
raised and compared under similar
environmental conditions
 i.e., 
same management practices
.
Progeny should be born
 in the 
same season
 and 
year
 as well as same
age/lactation.
All the 
healthy animals should be included
, and 
excluded those
 which
would 
not complete
 
lactation length.
Data recorded
 should be 
adjusted/corrected
 for environmental
effects such as 
year
, 
season
, 
lactation length
, 
lactation number
(parity)
, 
age
 etc.
More number of progeny
 should be 
recorded per sire
 to cancel out
randomly distributed sources of error.
 
Constraints in Progeny Testing:
Small population size
 
It can be solved by
i.
Associated herd progeny testing
ii.
Field progeny testing
Unplanned mating
 – this leads to wastage of data and non-
orthogonality of data.
 
To have equal number of daughter per sire mating
should be well planned.
 
Methodology of Progeny Testing:
To 
overcome population size
, the PT programme should be carried
out in 
associated herds
.
About 
4-5 males
 should be kept under test for 
each
 required
progeny tested bull.
About 
50 progenies
 should be settled from 
each bull 
to get about
10 daughters per bull
.
About 
8-10 bulls
 should be tested 
per batch
 to get atleast 
2 top
ranking bulls.
It is 
better to complete the test within the 
period of 2 years.
Atleast 
10,000 semen doses
 should be prepared and
cryopreserved from proven bull for AI programme.
 
Advantages of Progeny testing:
Progeny testing is suitable
 for
i.
 
sex limited traits
ii.
 
traits with low h2
iii.
 
slaughter traits
It increases 
intensity of selection
Accuracy increases with the 
increase in progeny number
.
Useful for 
identification of recessive genes
, if present, in
the bull put under test.
 
Limitations of Progeny Testing:
Time and cost
 is the main limiting factor.
Increases 
generation interval
genetic gain
 
per unit of time is l
ow.
 
 
 
 
THANK 
 
YOU
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Selection in animal breeding involves choosing the best individuals to improve specific traits. Criteria for selection include individual merit, competitive exams, and interviews. Selection of farm animals focuses on non-random reproduction of genotypes. Types of selection include natural and artificial selection, each influencing genotype and gene frequencies. The objective is to enhance desirable traits and response to selection, while considering effective population size.


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  1. ANIMAL GENETICS & BREEDING UNIT III Principles of Animal Breeding Theory Selection and its Basis Dr K G Mandal Department of Animal Genetics & Breeding Bihar Veterinary College, Patna Bihar Animal Sciences University, Patna

  2. Introduction to selection Choosing of best individuals among the lot. Objective of selection? For further improvement in a particular field. Various Fields are: i. Wining of medal in Olympic games & sports ii. Wining of Nobel Prize (Nobel laureate) iii. Literacy & Cultural events singing, dancing (Mr. India & Miss India) iv. Higher education IIT, IIM, IISc, AIIMS, Science & Technology, Vety. & Agri. Science etc. v. Service Adm.(IAS), Engineer, Doctor, Professor, Scientist, Judge, Officer, Army, School teacher etc.

  3. Criteria of selection Or Basis of selection? Individual merit only Method of selection: Competition Competitive exam Interview Competitive exam & Interview both Group discussion Physical fitness Medical test Accuracy of selection the factors which increase the efficiency of selection selection index or total score

  4. Selection of farm animals Definition: 1. According to Prof. I M Lerner: selection is the non- random differential reproduction of different genotypes. i. Differences in fertility among individuals in parent generation ii. Differences in viability among the progeny iii. Choice of mated individuals differential reproductive rates within the population whereby some individuals tend to have more offspring than the others. i. All individuals are not allowed to be the parents. ii. Difference in fitness from individual to individual. 2. According to Prof. Jay L Lush: selection is the

  5. Types of selection Natural Selection Selection operates through natural forces like fertility and viability. Nature selects individuals which are more adaptable and more fit in a particular environment. Artificial Selection Selection operates through intervention of man (animal breeder) Superior individuals will be allowed to be the parents for next generation. Natural selection favours artificial selection.

  6. Effect of Selection : i. There will be change of genotype frequency and gene frequency. ii. It increases the frequency of desirable genes iii. It does not create new genes in the population iv. As a result of selection there will be change of population mean. Objective of selection: i. To increase the mean value of performance traits in subsequent generations. ii. To maximize the response to selection. iii. To decide the minimum effective population size (Ne).

  7. Ne = Number of individuals that would give rise the same rate of inbreeding in every generation. 1 1 4?+ 1 4?? ?+? , and 1 1 8? + 1 4? or, Ne = 2?? = 8? ??= Where, S = no. of sires and D = no. of dams 1 The increase in inbreeding per generation is about F = 2??? Where t is the generation interval in terms of year. It is suggested that there should be sufficient Ne to reduce inbreeding, F, less than 1% per year.

  8. Criteria or Basis of Selection Breeding value is the only criteria of selection. Value associated with the genes carried by an individual is the B.V. The sources of information based on which the breeding value of an individual is estimated are called as the basis of selection or aids to selection or criteria of selection. Breeding value of an individual is estimated either from the phenotypic value of the individual itself or from the phenotypic value of its relatives. Information from relatives is very important to estimate the breeding value of an individual. Because there are certain percentage of genes which are common between individual and its relatives due to common ancestry.

  9. Use of information from relatives is very important to estimate the breeding value of the individual under the following conditions: i. When individual selection is not possible. a. Sex-limited traits milk production, egg production b. Traits can not be measured in living animals slaughter traits ii. When selection is required at the earlier age but the trait is expressed later in life. iii. When h2 of the trait under selection is low. The breeding value so obtained is known as estimated breeding value (EBV) or probable breeding value (PBV) or predicted breeding value.

  10. Basis of Selection The sources of information based on which the breeding value of an individual is estimated are called as the basis of selection or Principles of selection or Criteria of selection. 1. Individual Selection 2. Pedigree selection 3. Family selection 4. Within family selection 5. Sib selection 6. Progeny testing

  11. 1. Individual Selection Selection is made on the basis of own performance or own phenotypic value. When breeding value of an individual is estimated based on its own phenotypic value, then it is known as individual selection. Individual selection is also known as mass selection when selected individuals are kept together en mass for mating. Example: Drosophila and Tribolium Conditions applied for individual selection: (i) when traits are expressed in the individual and (ii) when h2 of the trait is high (iii) when mating records are maintained

  12. Estimation of breeding value : breeding value (BV) of an individual is estimated from the phenotypic value of the individual as a deviation from the population mean (selection differential) times the h2 of the trait and known as Probable Breeding Value (PBV). PBV = P + h2(Pi P) Where, P = Population mean, h2 = heritability Pi = phenotypic value of the individual

  13. Accuracy of individual selection: It depends on magnitude of rAP Correlation between breeding value and phenotypic value (rAP ) is equal to the square root of h2 (rAP = h) The accuracy of predicting the breeding value of an animal will be increased with the increase in magnitude of h2. Efforts must be made to get accurate estimation of h2 by reducing the environmental variations, and by estimating h2 based on repeated records of individual.

  14. Limitation of individual selection: 1. Cannot be applied for sex-limited traits. 2. Cannot be selected If the traits are expressed later in life or after death of individual (slaughter traits) 3. Traits with low h2 is the limiting factor. When h2 is low, the phenotypic value is the poor indicator of breeding value. Since, h2 = r2AP and accuracy of selection h = rAP.

  15. Advantages of individual selection: 1. Information of the individuals are easily available. 2. It can be applied before progeny testing 3. Used when pedigree information are not available 4. Generation interval is shorter in comparison to progeny testing 5. It gives direct estimation of BV. Does not depends on relatives. 6. It allows greater estimation of selection differential than the progeny testing.

  16. Aids to individual selection: Individual selection will be more difficult when: i. Heritability of the trait is low to medium ii. Information of relatives are not available When h2 of a trait is low, the repeated records of the same animal can be used for estimation of breeding value. Use of part records and genetic correlation among the traits will be helpful when earlier selection is practiced for the traits expressed later in life. 1. Additional records 2. Most probable producing ability (MPPA) 3. Use of part records

  17. 1. Additional Records: Useful for traits repeated in life time Milk production (LMY), Wool production, Egg production etc. Advantageous to predict BV based on mean of several records. h2 for mean of n records, with repeatability, r, is taken as: ? 2 1+ ? 1 ? Accuracy of selection using n records will be equal to h2n ? 2 1+ ? 1 ? Accuracy of selection for single record, rAP = 2 Relative efficiency (ratio) = rAP rAP = h2n = rAP = ? 2 ? 1+ ? 1 ? 2 = 1+ ? 1 ?

  18. 2. Most Probable Producing Ability (MPPA): Useful for the traits repeated several times in life time. Efficiency of producing ability or MPPA depends on number of measurements and repeatability of the trait. MPPA = M + 1+ (? 1)?(O - M) where, M = herd average r = repeatability n = number of measurements on the same animal O = Individual s own performance ??

  19. 3. Use of part records: Genetic gain by use of part records, G = bAP(XPi XP) where, bAP = regression of breeding value on part records Xpi = part record of individual animal XP = Mean part records of population (XPi XP) = Selection differential

  20. 2. Pedigree Selection Selection of an individual based on performance of its ancestors is known as pedigree selection. Pedigree is the systematic list or records of ancestors of an individual. Ancestors are parents, grand parents, great grand parents, etc. Pedigree having information on the economic traits of ancestors is useful for selection of an individual. Breeding value of an individual is estimated on the basis of performance of ancestors.

  21. Basis of pedigree selection: An individual is related by 50% with its parents, 25% with grand parents, 12.5% with great grand parents and so on. The relationship is reduced to half in each generation due to halving nature of inheritance. It is thus more important to consider recent ancestors (parents) than the remote ancestors for pedigree selection. Inclusion of more remote ancestors results only in marginal gain. Pedigree selection adds very little to the accuracy of estimating BV of an individual if information on individual are available.

  22. Significance of pedigree selection decreases when information are available either on individual or its family members (sibs & progeny). Guide to the pedigree selection: Degree of genetic relationship more closely related ancestors should be given more emphasis. Heritability of the character pedigree selection is more accurate for characters of high h2. Information should be available on ancestors.

  23. Advantages of pedigree selection: Allows selection at younger age. It is helpful in multistage selection. It is useful for sex-limited traits and traits expressed later in life or after death of animal (eg. slaughter traits). It is helpful when two individuals have similar performance but one belongs to a better pedigree. It is less costly, as only compilation of pedigree is required.

  24. Demerits of pedigree selection: Characters with low h2 can not be improved to the level of expectation. Some pedigree gets undue emphasis and favoured. Better environment is provided to the favoured pedigree. Pedigree selection provides no basis of selection among individuals when descendants are from the same ancestors.

  25. Estimation of Breeding Value (BV): The BV of an individual from pedigree records is estimated by the selection differential of its relatives (P) taken as a deviation from their contemporary average (Pc) times the regression of the genotype of the individual on the mean phenotypic value of the relatives (bAP) and added to the mean of contemporary group as: P.B.V. = Pc + bAP(P Pc) The bAP is taken as rh2 where r is the coefficient of relationship between the individual and its relatives. In estimating the PBV of an individual the record(s) of one parent or both parents or parents and grand parents can be used. The information on ancestors combined with individual s own record increases the accuracy of selection.

  26. Accuracy of pedigree selection: The selection based on the performance of one parent is half as effective (accurate) as that based on individual s own performance. The information on records of both the parents plus all the four grand parents gives lesser accuracy of selection which does not exceed 0.71 than based on individual s own record. The information on records of ancestors (both the parents plus all the four grand parents) combined with individual s own performance gives little higher accuracy of selection than based on individual s own record. The accuracy of selection based on single parent never exceed to 0.50.

  27. 3. Family selection Information from collateral relatives may be used for estimation the B.V. of an individual. Among the collateral relatives, full-sibs and half-sibs are more closely related to the individual. Full-sibs and half-sibs constitute full-sib family and half-sib family respectively. Selection of an individual on the basis of family mean is called family selection or sib selection depending upon inclusion or exclusion of individual s own performance in the family mean. Selection of an individual on the basis of family mean is called family selection when individual s own performance is included in the estimation of family mean.

  28. In family selection the criteria of selection is based on the performance of sibs plus individual s own record. Types Full-sib family selection & half-sib family selection. Family will be taken as a unit and depending upon family mean the whole family will be selected or rejected. If the family is selected, then the inferior individual of the family should also be selected. If the family is rejected, the superior individual of the family will also be rejected. Family selection is practiced for the following traits for which measurements of individual are not available: i. Traits with low heritability and high reproductive rate litter size

  29. Sib selection: Selection of an individual on the basis of family mean is called sib selection when individual s own performance is not included in the estimation of family mean. An individual is selected on the basis of average performance of sibs. Average performance of sibs is the criteria of selection. Depending upon types of sibs, it is two types Full-sib family selection and half-sib family selection.

  30. Sib selection is practiced for improvement of the following traits for which measurements of individual are not available: Traits with low heritability and high reproductive rate litter size Sex-limited traits milk production, egg production Traits can not be measured on the individual slaughter traits

  31. Advantages of family selection: It is suitable for traits with low heritability and high reproductive rate. Eg. Litter size in pig, egg production. It reduces generation interval. It is an aid to individual selection because it is better to select an individual from a superior family. Limitation: It leads to inbreeding Full-sib family selection can only be applied in species with high reproductive rate to get large family size. Family selection is costly since large number of families are required to be maintained.

  32. 4. Progeny Testing Selection of an individual based on it s progeny performance is known as progeny selection or progeny testing. It is the most important basis of selection. Mean phenotypic value of the progeny is taken as the deviation from mean phenotypic value of contemporaries. Each progeny inherits one-half of the genes from each parent due to halving nature of inheritance. This is taken as transmitting ability of the parent. Hence B.V. of the parent is twice the mean deviation of the progeny from the population mean. B.V. = 2(M P) Where, M = progeny mean, P = population mean

  33. Superiority of P. T. over other selection criteria: Individual selection is not possible for traits of low h2, sex limited traits and the traits expressed after death of individual. Pedigree selection is based on performance of dams. Due to halving nature of inheritance it is not possible to know that which half (better or inferior) of dam s genes is received by the progeny. Accuracy of sib selection is also low due to sampling nature of inheritance. In progeny testing, the performance of many progenies gives the best and most reliable information about the genetic merit of the individual (parent).

  34. Precautions in Progeny Testing: Adult females should be allotted randomly to all the sires under test to avoid the effect of dam on progeny. Different sire groups should be raised and compared under similar environmental conditions i.e., same management practices. Progeny should be born in the same season and year as well as same age/lactation. All the healthy animals should be included, and excluded those which would not complete lactation length. Data recorded should be adjusted/corrected for environmental effects such as year, season, lactation length, lactation number (parity), age etc. More number of progeny should be recorded per sire to cancel out randomly distributed sources of error.

  35. Constraints in Progeny Testing: Small population size It can be solved by i. Associated herd progeny testing ii. Field progeny testing Unplanned mating this leads to wastage of data and non- orthogonality of data. To have equal number of daughter per sire mating should be well planned.

  36. Methodology of Progeny Testing: To overcome population size, the PT programme should be carried out in associated herds. About 4-5 males should be kept under test for each required progeny tested bull. About 50 progenies should be settled from each bull to get about 10 daughters per bull. About 8-10 bulls should be tested per batch to get atleast 2 top ranking bulls. It is better to complete the test within the period of 2 years. Atleast 10,000 semen doses cryopreserved from proven bull for AI programme. should be prepared and

  37. Breeding Value: The breeding value of bull = Pc + bAP(Pi Pc) Where, Pc = Contemporary progeny average i.e., average of all progeny performance under all the bulls put under test. Pi = Progeny average of a particular bull. bAP = regression coefficient i.e, regression of B.V. of parent on the phenotypic performance of the progeny. bAP = rnh2 / [1+(n-1)t] = 0.5nh2 / [1 + (n-1)t = nh2 / [1 + (n-1)0.25h2] = 2nh2 / [4 + (n 1)h2] (Pi Pc) = selection differential PBV = Pc + b(Pi Pc) = Pc + 2? 2 4+ ? 1 2 (Pi Pc)

  38. Advantages of Progeny testing: Progeny testing is suitable for i. sex limited traits ii. traits with low h2 iii. slaughter traits It increases intensity of selection Accuracy increases with the increase in progeny number. Useful for identification of recessive genes, if present, in the bull put under test.

  39. Limitations of Progeny Testing: Time and cost is the main limiting factor. Increases generation interval genetic gain per unit of time is low.

  40. THANK YOU

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