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This presentation
has been created by Stanislav
Socha, University of Siedlce.
This lecture will be concerning
genetic parameters, repeatability and genetic correlations
Modul no. 3: Improvement of Animals
The genetic parameters
of the population include heritability of features, repeatability of features and correlations,
including genetic phenotypic and environmental correlations.
Further,
characteristics important
in animal husbandry include performance of animals.
For example, milk yield, animal reproduction and health.
Generally, the features can be classified into two groups.
Quality features and quantitative characteristics.
The main factor
differentiating these two
groups of traits is the number of pairs of alleles genes affecting their formation
and the number of classes of differentiated phenotypes.
In the case of qualitative traits.
The number of pairs genes or a series of alleles
influencing their formation is limited, ranging
from one to a maximum of 2 to 4.
This, in turn affects a limited number of genotypes.
Hereditary assumptions of individuals and consequently individuals with specific phenotypes.
Total characteristics of the organism.
In the case of features
defined as quantitative, the situation is much more complex.
Firstly, the number of genes polygens
affecting their shape is very numerous, sometimes difficult to determine.
Then, in addition to genetic assumptions,
environmental factors have a significant impact on their formation.
This type of inheritance significantly increases the diversity of individuals in the herd
and makes it extremely difficult to identify genotypes
based on phenotype.
With the multiplicity of factors influencing traits
it is impossible to determine the contribution of a single gene to the formation of a quantitative trait.
Only statistical methods allow to determine the influence of genotype and environment on the variability
of the trait in the herd, and to estimate the heritability of the traits of interest on this basis.
And if
each heritability H2
informs us in a very general sense
about what part of the general phenotypic variation of a given trait in
the population is genetic variation diversity caused by the action of genes.
Heritability also determines how much of the selection difference will be transferred
to the offspring in the form of breeding progress.
The heritability of traits is measured
by the heritability coefficient h two.
It is the ratio of genetic variation to phenotypic variation.
We can express this with the formula
H two equals delta two G slash delta 2P
where Delta 2P equals delta 2G plus delta 2E.
Were delta 2P - phenotypic variability,
total variable ity of a given trait in a herd population.
Delta 2G - genetic variation, delta 2E - environmental variability
Discover
ratio of genetic variation to overall phenotypic variation.
The degree of influence of the variability of the hereditary assumptions
of a given trait on the manifestation of variability in the phenotype.
The regression coefficient of the breeding value against the phenotypic
value of the same individual (refers to the population)
After
a note,
it makes it possible to determine to what extent the observed phenotypic
variability results from genetic variability
determines the regression of G against P allows
to predict
estimate the breeding value.
Allows you to predict the effectiveness of selection
because
h to the symbol derived from the analysis of variance
refers to the mean square of deviations of some of its components.
H to correlation between genotype and phenotype.
But again, that this is not the problem, the more we divide
Analysis of variance, we estimate the mean and variance
for the whole population.
for all groups of half siblings.
for all sibling groups.
We rely on analysis of
Half sibling groups.
Cattle, sheep,
and full sibling groups.
Poultry, pigs.
We calculate on the basis of intraclass correlation coefficients
analysis of full sibling groups
h2 → population parameter
Varied depending on the characteristics.
Varied depending on time in the same populations.
Varied depending on the population.
For the same features H2 from 0 to 1
or from 0 to 100.00%.
Group
The repetition of traits
is one of the genetic parameters of a population.
The repeatability of traits can be estimated for traits that are cyclically repeated in animals.
For example, the number of young in successive litters, body weight of successive litters,
the amount of milk obtained from cows and other mammals in successive lactation
When estimating the repeatability index.
We assume that the genotype of animals does not change over the course of their lives
and the differences that arise in subsequent years of use
result from environmental influences.
They can also result from the somatic development of animals.
Estimating the repeatability index
(r’, R): P = H + EES + EEN
OR σ2p = σ2g + σ2Es + σ2En
σ2p - phenotypic variability
σ2g – genetic variability
σ2Es – constant environmental variability,
σ2En – variable environmental variability.
regression method of posterior performances,
regression method of later performances
to earlier performances
Estimating the repeatability index
(r’, R):
P = H + EES + EEN OR
σ2p = σ2g + σ2Es + σ2En
σ2p - phenotypic variability
σ2g – genetic variability
σ2Es – constant environmental variability
σ2En – variable environmental variability.
r’ = (σ2g + σ2Es)/(σ2g + σ2Es + σ2En)
The method of regression
of later performances to earlier performances.
Variance analysis Method Selected values
of estimated repeatability ratios.
number of piglets in pigs.
0.1 - 0.15
Number of young in rabbits.
0.09 - 0.12
number of young in chinchillas 0.12 - 15.
repeatability of milk yield
in cattle 0.25 - 0.35
Correlations result from linkage
of genes - conditioning individual traits are on the same chromosomes.
Selection of two features in the same direction, which in turn leads to the occurrence of interdependence.
Pleiotropic influence of individual genes on various traits
With low heritability of traits
the value of the phenotypic correlation is close to the environmental correlation. With high heritability,
the phenotypic correlation will be close to the genetic correlation.
In the case of medium sized heritability,
or when one trait has a high and the other a low
the genetic correlation and may be positive and the phenotypic
correlation negative.
VALUES OF SOME PARAMETERS IN ANIMAL HERDS - HERITABILITY
Cattle: milk yield 0.31 0.39
Fat content 0.56 - 0.68,
Milk Protein
content about 0.57.
Body weight at birth about 0.40.
Body weight at the age of 120 days, about 0.50 daily gain of about 0.40.
Slaughter efficiency of about 0.60.
Height of the withers about 0.542.
Carcass length about 0.75.
For area of the eye of the tenderloin about 0.178.
Pigs:
Daily gain 0.30.
Average daily gain 4290 kilograms 0.26
for fat thickness on the back about 0.50.
Length of the carcass about 0.50.
Amount of meat in basic cuts
about 0.520.
Area of the eye of the tenderloin about 0.740.
Lighter weight three weeks approximate 0.080
litter size at birth is about 0.10.
Sheep: body weight at birth 0.30.
Body weight after weaning 0.30.
Body weight ten months 0.28.
Shearing Pure fiber Efficiency 0.28.
Wool thickness 0.40.
Human Mass 0.40 000.
Wool Height 0.52.
Milk Yield 0.18.
Fleece weight of the second shearer 0.32.
Poultry:
egg size 0.45.
Egg weight 0.30.
Laying capacity 0.20.
Shell Color 0.70.
Fertility 0.10.
Feed Efficiency 0.60.
Body weight eight weeks 0.10 - 0.30
Stroke Length 0.10 - 0.30
Cattle correlations
with milk yield fat content in milk dash zero 41
phenotypic 0.43 Genetic
fat content Protein content in milk
0.57 phenotypic 0.60.
Genetic weight at birth at the age of one year.
0.34 phenotypic 0.40.
Genetic trunk length body weight 0.70 phenotypic 0.83.
Genetic Poultry Body weight Egg weight
0.30 phenotypic 0.25.
Genetic body weight Breast Angle
0.38 phenotypic 0.68.
Genetic body weight Stroke Length
0.4120.74 phenotypic 0.832.
0.89. Genetic.
Pigs daily gain back fat thickness
-0.10 phenotypic -0.20.
Genetic body length Back fat thickness -0.30
phenotypic -0.40.
Genetic.
Thank you for your attention.