My name is Ewa Wójcik, I am an employee of the Institute of Animal Production and Fisheries at the Faculty of Agricultural Sciences of the University of Siedlce.
I would like to present the topic of genetic traits in animal production.
Production characteristics are those characteristics that have enormous economic significance.
Mainly belong to the category of quantitative characteristics.
The inheritance mechanism of these traits is very difficult and complex to explain.
The variability of these traits also depends on environmental influences.
Quantitative traits are controlled by multiple genes at different loci.
They are also known as polygenes, polymeric genes, cumulative genes, or additive genes.
Polygenes interact to create a trait, and the effects of individual polygenes.
They add up and determine the intensity of the trait.
The number of polygenes controlling quantitative traits is unknown.
Each of the polygenes has two alleles with intermediate inheritance.
One of the alleles always has a positive character, while the other is neutral.
Positive allele effects from individual loci are equal.
The effects of these genes add up in shaping the phenotype.
Examples of such characteristics may include height, weight, growth rate, performance, circumference,
surface whether it's parts of the body or the whole body.
These features are always expressed using units of measurement such as meter, square meter.
cubic meter, kilogram or other units of measurement.
Phenotypic expression of quantitative traits is highly dependent on environmental factors.
They can enhance or weaken the action of polygenes.
With the appropriate genotype and environmental influences shaping and influencing the phenotype,
we can obtain a higher phenotypic value from a given animal,
providing the animal with appropriate living conditions.
Another environmental factor is the maternal effect and although the number of chromosomes,
which an individual receives from their parents is the same,
The influence of the mother on offspring is greater and stems from three basic sources.
First of all, from the genetic background, i.e. extranuclear mitochondrial inheritance,
influence of the mother's environment during the prenatal period, also known as the prenatal effect
The postnatal environmental influences on the mother after birth, or the postnatal effect.
These features may have a continuous nature, with the value of the feature in the population.
It can take any value between maximum and minimum.
The value of this trait in an individual can circulate anywhere within this range.
The number of possible phenotypes in practice is unlimited.
And an example of such a trait could be milk production.
The second category of features is jump features.
The values of these features are expressed by a number of specified units.
In the population, the trait ranges from minimum to maximum values.
The value of features for a specific individual must be expressed in whole number units.
An example of a jump trait could be the number of eggs laid or the number of offspring in a litter.
The next threshold traits are conditioned by the influence of multiple genes and environmental factors.
Usually they exhibit two or very few phenotypic forms.
Genetic variability is heritable, while phenotypic variability is qualitative in nature.
very often binary. An example of such features is disease resistance.
This trait manifests either through experience or death, with no in-between states.
Another example is the litter size in large animals, which typically give birth to one offspring.
but sometimes they can give birth to twins or triplets.
The property of a threshold trait is the so-called threshold to which the genes referred to.
which crossing results in an elemental phenotypic change.
The distribution of a characteristic is a parameter that describes the population and informs us,
What proportion of individuals in a population exhibit each possible value of a trait,
Each possible phenotype. The description of the distribution of the trait depends on the number of phenotypic classes.
The greater the number of phenotypes, the more difficult it is to describe the distribution of a trait.
We distinguish between continuous, jump, and threshold distributions.
Distribution of phenotypes in case of continuous distribution, most of these quantitative traits.
It corresponds to the bell curve, or normal distribution curve.
This is the distribution that most individuals obtain.
characterized by values of the measured feature to the average,
It takes the least extreme values, above and below average.
The normal distribution is symmetric, with the axis of symmetry passing through the mean.
The parameters for the normal distribution are the mean and standard deviation.
Jumping distribution describes the abundance of different phenotypic classes.
how many of them we have.
Progressive distribution, in turn, describes the number of each.
Most commonly two categories of phenotypic classes.
Category A, Category B.
The environment has a huge impact on the intensity of a given phenotypic trait, enhancing it to varying degrees.
Increasing or decreasing values.
The increased variability of the trait is a result of the appearance of environmental effects.
Difficulty in determining the genotypic value of individuals.
Then the curve is more flattened compared to the Gaussian curve.
The phenomenon of transgression is associated with quantitative features.
Livestock animals are heterozygous for a significant number of genes.
offspring may exhibit higher trait values due to crossing such individuals
lower than their parents.
This phenomenon is called transgression and is widely used in breeding work.
Genes with large effects are also associated with quantitative traits.
so-called QTLs, Quantitype Atriot Locus.
The graphical distribution of phenotypes for some traits significantly deviates from the normal distribution curve.
This is the result of inheritance, when polygenic genes are also at play.
Genes with a large effect, known as QE genes.
He is identified as a homozygous recessive when the trait values differ.
exceed at least one standard deviation.
Perhaps then the normal distribution can be skewed to the left or right.
Examples of genes with large effect on various production traits in cattle
For example, there is the growth hormone GH which affects higher milk production.
compared to homozygous dominant individuals.
It also affects meat utility traits, growth rate, and carcass composition.
together with the insulin-like growth factor gene.
It also affects the length and circumference of the chest, the aging process.
reproduction and the immune response of the organism.
Gen ten odpowiada za niektóre zaburzenia rozwojowe, tak jak karłowatość czy akromegalia.
also identified in poultry.
The next major genes found in cattle are milk protein genes.
It contains kappa casein. It is related to the properties of milk functionality.
such as milk yield, protein yield, fat yield.
Milk with kappa casein B gene has higher protein content and better suitability.
to cheese production compared to milk with the kappa casein variant A.
Another gene, the beta-lactoglobulin gene, affects milk yield and its components.
Milk containing beta-lactoglobulin B differs from milk with the A variant.
higher dry matter content, fat and casein content, and better technological suitability.
Another gene, the diacylglycerol acetyltransferase gene, affects milk yield.
protein and fat in milk and intramuscular fat content.
Muscle hypertrophy, in turn, increases the lean meat content in the carcass.
Better dietary properties due to reduced fat and connective tissue.
This trait is highly preferred by breeders of both purebred cattle breeds.
From Belgian Blue cattle as well as their crossbreeds.
Unfortunately, genetics also have a negative impact, for example delaying the onset of sexual maturity in both males and females.
It affects reduced fertility in male goats, lower concentrations of sex hormones in the blood serum.
smaller circumference and mass of the nucleus. In cows, pregnancy is prolonged and fetal mass is increased.
which causes many problems during natural childbirth.
In pig, the main gene for malignant hyperthermia is the ryanodine receptor I gene.
It increases pigs' susceptibility to stress by inducing the so-called PSS syndrome.
It may be caused by stress on transportation, thermal conditions, chemical factors.
As a result of these stress myopathies, unfavorable physicochemical changes occur in the body.
Deterioration in meat quality, discoloration, unpleasant odor, excessive softness, and watery texture.
Gen ten jednocześnie dodatnio wpływa na niektóre cechy związane z użytkowością mięsną np.
meat content in the loin eye surface, which is most beneficial in heterozygotes
being carriers of this mutated allele. Such animals are good material for fattening.
Gentian also occurs in other species such as cattle, horses, and humans.
Sour meat gene, gamma protein kinase C subunit gene
Mutant allele carriers have twice as much myogenin content in their muscles, especially in the hamstrings.
Another main gene, insulin-like growth factor 2, influences meat quality traits.
increased muscle mass, decreased back fat content.
Another major gene, a gene influencing litter size, naturally affects fertility and litter size.
Litters with two copies of this gene in their genotype produce 1 to 1.4% more offspring.
compared to non-carrier dams.
In sheep, the main gene is the muscle hypertrophy gene, which causes a 32% increase in muscle mass.
Reduced fat content by about 8% and improved feed efficiency.
Another high-fertility gene, causing a high degree of ovulation in sows,
affects the development of Graafian follicles and corpus luteum, decreased secretion
inhibitors of hormones acting on gonadotropins and increasing ovulation,
increasing the fertility by about one lamb.
Knowledge of genetic variability is particularly important in breeding work.
in the phenotypic variability of a given quantitative trait.
The estimation of this proportion uses heritability, which we can express as
Using the formula where heritability equals the ratio of genetic variance to total phenotypic variance.
from genetic to phenotypic variability.
Inheritance determines the strength of the relationship between an animal's phenotype.
The genetic value of individuals for their offspring, i.e. breeding value.
If a trait is highly heritable, then the animal's phenotype is very good.
source of information about his genes.
When heritability is high, greater phenotypic similarity is observed.
between closely related individuals, for example between full
sibling, half-sibling or between parents and their offspring.
This is because these animals share a large portion of the same genes.
for example 50%, 25% in the case of half-siblings or 50% between parents and offspring.
If the contribution of genetic variability to the total variability of a trait is small,
Then based on the phenotype, we can't say much about the value of the animal's genes.
what he will pass on to his offspring.
Inheritance coefficient magnitudes for meat cattle traits
They are mostly highly heritable, shaping up at various levels.
For example, if the tusk length is 0.75 and we have a low heritability coefficient.
Surface area of the eye of round muscle is 0.18. Size of hereditary coefficients.
for most dairy cattle, typical traits are mostly lowly heritable.
ranging from 0.15 to 0.45. High heritability is the percentage of protein in milk trait values.
The heritability coefficients for sheep traits are diverse.
both at the low and high heritability levels.
In most cases, we have examples of traits that are low in heritability, high in heritability can be subjected here
body weight on the hundredth day of life or clean fleece weight, or wool yield.
When it comes to the magnitude of heritability coefficients, heritability for pig traits
These parameters are low level shaping. High level of heritability coefficient
This is the surface of the eye sclera or the amount of meat in primal cuts.
The heritability coefficients for example traits in chickens are also low.
We can mention the highly heritable trait of shell color in the case of non-shell traits.
at a level of 0.7 or in the case of meat characteristics when feed is used.
Thank you very much for your attention.