Good morning, my name is Katarzyna Andraszek, I am a professor.
I work at the Institute of the University in Siedlce.
Animal Husbandry and Fisheries at the Faculty of Environmental Sciences.
The topic of my presentation is the effects of crossbreeding and I would like to dedicate time
just various types of crossing effects and also different crossings,
which are used in breeding work.
Crossbreeding is a mating system that involves combining animals together.
animals representing two or more dissimilar genetic groups
Crossbreeding is the opposite of inbreeding, but even here
In some cases, inbreeding, or mating of relatives and crossbreeding.
they can intersect with each other, they can complement each other.
The goals that can be achieved through crossbreeding are very diverse, and it is precisely these
These form the basis for dividing the association system into a variety of distinct methods.
Procedures can generally be divided into two main groups by assuming
as the main criterion of breeding intention.
First, crossings aimed at using and adapting foreign genes.
in a herd or some population and the other effect is intentions towards utilization
phenomena of heterozygosity, known as hybrid vigor.
This diagram shows crosses in a very synthetic way, so we have
Crossing for utilizing heterosis effects and here we distinguish crossings
non-domesticated individuals, including interspecies crossbreeding,
Alternating and rotational. When crossing zebroid lines, we have a whole series of
from peak to interbreeding, intraracial towards
periodic selection and alternating periodic selection and the second group of crosses are these
Crossing for the purpose of adapting foreign genes, and here we distinguish crossing.
elevating, displacing, and divisive.
Crossbreeding can increase production levels in two ways. Crossbreeding provides
Breeder the ability to combine desired traits from two or more breeds
This is how a higher overall level of performance in individual features is achieved.
Among hybrid animals than if it could be achieved within a given
specific group. It is often referred to as racial complementarity.
Strengths of one race that complement or cover the weaknesses of the other race.
Another way in which crossbreeding increases productivity is by increasing the yield.
level of performance in specific traits as a result of heterosis.
Increased productivity may result from heterosis exhibited in the offspring of hybrids.
Breeders have long known that hybrids exhibit a variety of traits, including
Utility can exceed the value of both parent forms.
This phenomenon is known as hybrid vigor and was later named by American breeders.
Genetic Shull heterozygosity thus expressing the combination with a heterozygous state
genotype as the desired state. Heterozygosity is manifested not only in increased
at a higher level of most economically important functional traits such as, among others.
Milk production in cattle, egg-laying capacity in chickens, higher body weight in many species.
Mainly in terms of overall hybrid vigor compared to
With the output forms. Hence another name for heterozygosity.
like vigor of hybrids. Now I would like to discuss crossbreeding methods aimed at
utilization and adaptation of foreign genes in the population.
Crossing over is not designed to yield immediate heterozygous results.
His goal is to achieve a lasting breeding effect in the form of
Improvement or correction of certain flaws of one race by another race.
Transformation of a primitive race into another that is at a higher level
breeding or finally creating a new breed based on existing breeds.
It should be noted that these actions must always be accompanied by constant care.
to improve environmental conditions. This is an essential condition for obtaining
depending on the specific breeding goals.
Several methods of interspecific crossbreeding can be distinguished.
The first is selective breeding. It is used in case of,
when a certain animal species basically meets the demands placed on it
However, it does have some flaws that should be corrected.
In such a situation, individuals from a different race can be used for correction.
having this perfect quality particularly well expressed.
In the context of breeding, polygamy is commonly chosen for this purpose.
Males of an aristocratic breed, distinguished by well-defined features,
which will be ennobled.
Crossbreeding is usually done once, using the resulting offspring for further pairings.
offspring of mixed blood, gradually moving away from the improving race.
Crossbreeding should be accompanied by very strict selection.
Don't explain and only return translated text.
whether to improve a specific trait by using genes from a different population.
Selective breeding doesn't necessarily have to be limited to primitive breeds.
however, there is most often used for example cattle breeding.
Danish red cattle.
Even races at a high level of farming culture are often forced to
Do not use genes from other races. For example, many Western European
Crossbreeding of dairy cattle breeds with Shorthorn bloodlines for improvement.
meat utility.
A staggered intersection is an intersection used to
resemblance of one race to another with higher utility value.
It is possible to effectively improve the breed that has utility at its level.
it represents a certain value. If we are dealing with a primitive race,
A one-time blood transfusion won't help much. A more effective approach would be to use
eliminating unwanted traits from the breed.
It replaces male breeders with breeders of the displacing race.
The obtained female hybrids are again crossed with males of the dominant breed.
And so the cycle repeats for several generations.
After 6 generations of selective breeding, the herd should have
98,3 of the blood race is replaced and becomes similar to it.
Then the breeding is usually continued without further crossbreeding.
Apply only to the most desired type of user.
This type of crossing is the fastest and most efficient way.
transformation of inefficient races. Its success largely
It depends on the proper choice of displacing race, which must be well
adapted to local natural-environmental conditions.
The next crossing in this series is a race-crossing.
If none of the existing races meet the conditions of a specific region.
On the other hand, local primitive races do not satisfy with their level of utility.
Do not attempt to create a new race, which on one hand
not conforming to economic demands, but will be fine
adapted to existing environmental conditions.
The material for crossbreeding should not be limited to just two races.
[but also dependencies on requirements for the type of use and possibly]
general biological properties of the future race.
The participation of different races in creating the new is usually not equal.
They are used depending on the characteristics we want to inherit from them.
There can also be no specific provision for creating a new race.
Every such action is very individual depending on the ultimate goal.
what we want to achieve and the conditions accompanying this process.
Breeding works conducted in Poland can be an example of race-crossing.
Mountain sheep or long-haired sheep.
The Puławska pig breed and the autosexing chicken breed were also created in this way.
rasa polbar.
Sharp selection must accompany in the method of crossbreeding.
leaving individuals for further breeding with a type most similar to the desired one.
Often also after the crossing period to quickly establish advantageous
The properties of animals intended to be the foundation of a new breed must undergo selective breeding.
Another large group of crosses are aimed at utilizing the phenomenon of heterosis.
Crossbreeding animals to achieve a heterozygous effect
In the first generation, crossbreeding was generally referred to as utility crossing.
The offspring of animals from different breeds typically exhibited
better expressed functional features compared to both parent input forms.
Heterozygosity is a transient phenomenon and cannot be maintained due to segregation in the next generation.
To obtain a heterozygous generation, let's always maintain breeding FX.
Purebred parental forms.
The occurrence of heterozygosity is not always certain.
Sometimes, the offspring exhibit an intermediate phenotype in relation to the most interesting traits that breeders cultivate.
or even less frequently, but less favorable than parents.
Many useful crossover methods have been developed in search of the most effective ways to combine solutions.
The first method is alternate crossing, where hybrids must be continuously obtained from pure parental breeds.
It is difficult to apply in practice and not always cost-effective because these animals are not used for breeding.
for the purpose of breeding to renovate the herd.
Interbreeding involves consistently backcrossing hybrids with one and then the other parent race.
This method is not limited to the exclusive utilitarian maintenance of hybrids.
Females are also used for reproduction, which partially eliminates the shortcomings of the previous method.
The heterozygosity of hybrids resulting from backcrossing changes slightly from generation to generation.
And never reaches as high a value as the F1 generation resulting directly from crossing two races.
In theory, the heterozygosity of subsequent generations should be around one third of the heterozygosity of the first generation hybrids.
The practical results achieved mainly in pig farming roughly confirm these assumptions.
This method in practice may be slightly less efficient than the direct performance of blends.
However, the end result is very profitable as it does not require the constant maintenance of two purebred herds.
For this purpose, you just need to have the right number of males from both parent breeds.
while the female materials are already selected blends.
Crossing of inbred lines within and between races.
Heterozygosity results in the phenomenon of heterosis.
The symptoms of hybrid vigor were known before the theoretical justification of this phenomenon was found.
When it was found based on a very large number of observations,
that heterosis arises as a consequence of the heterozygous state of hybrids,
Efforts were made to identify the most effective mating methods leading to maximum heterozygosity.
Inbreeding in breeding genetically homogenizes the lines where it is used.
and at the same time moves apart lines that are not related to each other.
Realization of this phenomenon has led to the development of many very modern association methods.
aiming to achieve heterozygosity, with the common feature of crossing animals from closely related breeding lines.
Crossing between inbred lines.
Crossing involves combining individuals from different lines.
within which the animals intended for crossing come from inbred lines.
This system has been most widely adopted in chicken farming.
The results of numerous experiments are known that indicate the high effectiveness of this method.
Next to the single crossing of two breeds or two lines, double crossing can also be used.
When the input material consists of four races.
If we label them as ABCD, initially to obtain heterozygous hybrids FX, we cross animals from the AB and CD line breeds.
In order to maintain the vigor of hybrids in the next generation, hybrids between A and B as well as C and D can be crossed with each other.
This way we obtain four-way crosses or we also call them four-line crosses.
Crossing inbred lines within a breed is a variation of the previous method.
The difference is that inbred individuals from the same line are crossed with each other due to inbreeding.
genetically can vary significantly.
The selection of individual lines for intersection may be preceded by trial associations to find
most suitable in terms of heterozygosity achieved in the hybrid generation.
The next crossing is periodic selection for the heterozygous effect.
Crossing of closely related lines is always a costly procedure, and also always associated with the risk of not achieving the intended goals.
This is the appearance of heterozygosity to such an extent that it would justify the excess breeding costs of inbred lines.
Search for new methods of obtaining heterozygous hybrids with lower costs and associated risks.
A method of periodic selection has been developed.
She recommends that the initial heterozygous population be crossed experimentally with a highly inbred line.
Such crossing offspring is subjected to a thorough evaluation by selecting pairings.
resulting in the highest heterozygosity in the offspring.
Animals from the heterozygous herd that crossed with zebroid individuals yielded the best results.
are now being bred within their own herd.
Selection for heterozygote advantage occurs from generation to generation until the most beneficial results are achieved through inbreeding.
This line, which due to its role can be called a test herd,
used for association with a heterozygous herd and for evaluating both female and male material,
because the hybrids are not used as breeding material in this method,
They only serve as a test for their parent's evaluated herd.
The next cross in this series is alternate periodic selection for heterosis effect.
This is also a modification of the previous method.
Through association checks, which result is the selection criterion within the stat.
It also aims to obtain balanced trait statistics for optimal utility in producing heterozygous hybrids.
In contrast to periodic selection, in this method, not a single inbred test herd is used for crossbreeding validation.
but two loci are unlinked and therefore highly heterozygous.
The method is very interesting because of the genetic implications it carries.
Selection aimed at the usefulness of both traits for producing heterozygous hybrids leads to gradual homogenization within each of them.
This limitation of variability is mutually directed to beneficially complement the genotype of an individual from the opposite herd.
If we accept the theory of overdominance as an explanation for the phenomenon of heterozygosity,
theoretically the best complementarity of genotypes of both parents should be achieved then,
when all genetic loci expressing dominance are in a homozygous state.
This method leads to an increase in homozygosity within the herd.
In cases of inbreeding, the homozygosity of individual genetic loci is randomly determined.
Under periodic selection, the homozygosity of interacting genes is established.
is most beneficial when crossing with a specific herd.
Genetic consequences of crossing over.
The genetic effects of crossing are the opposite of the genetic effects of inbreeding.
Hub stress causes depression with a reduced reproduction rate, decreased offspring viability.
reduced rate of growth with delayed sexual maturation and delayed attainment of physiological maturity.
Generally, the same characteristics that show the highest depression in a hub node.
the same traits that show the greatest heterozygosity during crossing.
There are two basic genetic requirements for a trait to exhibit heterozygosity.
To avoid genetic diversity between crossed races,
and there must be certain non-additive genetic effects for a given trait.
Failure to meet any of these conditions in the case of a specific crossword puzzle,
would not exhibit heterozygosity.
In such a case, the expected offspring outcomes of the hybrid would simply be the average performance results.
Both pureblood parents participating in the crossword.
In the case of traits expressing heterozygosity, the magnitude of heterozygosity will depend on
Always from the degree of genetic diversity between two parental races.
Genetic diversity refers to the degree of similarity or difference in genetic makeup.
between the two races. Races of similar origin and which during development are expected to
have been subjected to similar selective pressure, they will be much more genetically similar.
than races of completely different origins and chosen for different purposes during their development.
Negative gene effects refer to types of gene actions that exist in reference
Many pairs of genes are involved in the expression of a specific trait.
These effects can be divided into two categories. Non-additive gene effects, which are expressed
In individual gene pairs based on the level of dominance and non-additive gene effects,
that result from the interaction between gene effects at a specific locus
The influence of genes on one or more loci is referred to as epistasis.
Epistatic gene action involves combinations of genes at one locus interacting with effects.
combinations of genes from other loci. There are many different types of epistatic effects,
but their relative impact is very difficult to measure due to their complexity.
It seems unlikely that these epistatic effects are the main cause of heterosis.
In the case of most herds. The aim of crossbreeding is to achieve certain desired goals.
These include achieving heterosis and the ability to quickly activate desired traits.
Genetic material and the chance to combine several desired traits in animal breeding.
Heterozygosity, or the exuberance of hybrids, is associated with a maximally heterozygous state of the genotype.
Many different methods have been developed for obtaining heterozygous hybrids. Many of them are based on
For the initial kinship breeding and then crossing of inbred animals among themselves.
The possibility of using different crossing methods depends largely on the fertility of the species.
Complementary combination of crossed varieties or races and additional impact of heterosis
makes crossing a very important breeding system in commercial production systems.
Thank you very much for your attention.