1. I have an 8-month-old British kitten (by the way, Mario is our grandfather on my father’s side). After some time, the question of reproduction will arise, I would like to know: in order to breed a cat with a cat, do you need to first go to an exhibition? Or can you just invite a cat or buy one? And if you buy, then for good kittens you need to choose a cat of what line and what “show” quality?
Answer: if you want to get high-quality British kittens, then you must definitely present your cat to a court of experts at an exhibition in order to receive a certificate confirming his right to breeding work. Either buy a cat or invite it with documents. It is desirable that the pedigrees of the breeding cat and the cat have a common distant relative of high quality.
2. Please tell me, if the kitten’s parents are siblings, what could happen to its health and its offspring?
Answer: With close inbreeding, mutations appear immediately. Sometimes inbreeding produces remarkable results, although there is also a risk. But if everything is fine with the kitten now, then there is no reason to worry. Only in the future it is better not to cross him with relatives.
3. We are preparing to resolve the issue of sterilization. I already had experience with a sterilized cat - it’s so sad to look at her and know that she won’t be able to be a mother. But as far as I understand, there is a class of cats that is not suitable for breeding. How to find out what class my kitty is?
Answer: to do this you need to show your pussy at least once in front of competent judges. Cats that receive a rating of at least “very good” are accepted for breeding. And if she receives the title of Champion, then in the future there is no need to exhibit her. Confirmation for breeding use is no longer required.
4. What should be done if the cat does not have a pedigree? Breed: Scottish Fold. When purchasing him, I was offered to buy his pedigree, but I refused. Now I would like to give him away for breeding, but I have not kept contact with the breeder. Is it possible to somehow restore the pedigree? Or is it not necessary for mating?
Answer: if the cat does not have a pedigree and there is no way to restore contact with the breeder, for example, through the club to which the nursery where you bought the kitten belongs, then the only way out is to castrate the cat, since the breeding career is closed for him. To breed pedigree cats, producers must have a pedigree.
5. First you need to participate in exhibitions, and then breed a cat, or vice versa, which is correct? And one more thing: in order for the kittens to turn out blue, which cat (what color) should I breed my kitten with? I have it: British shorthair breed. Breed and color code: BRI n 24. Gender: 0.1 Female. Color: black spotted. She looks like a tiger cub!
Answer: the cat must be exhibited and it must receive a rating of at least “very good”. Moreover, this must be repeated before each new mating. Either the cat must receive the title of “champion”, then she can be bred without confirmation of breeding status.
It is not enough to know the color of your cat; you need to imagine the colors of all its ancestors up to the fourth generation. In addition, it is necessary to study all the ancestors of the blue British cat up to the fourth generation and compare the pedigrees of the alleged sires. This is quite painstaking work. If you have no idea about the genetics of colors, then you are unlikely to cope with it. Then the “trial and error” method remains. Maybe some litter will produce a blue kitten.
6. Tell me, my cat is tortoiseshell. Black with cream. Which cat should I breed her with?
Answer: depends on what you want to get. You should not breed with a blue cat, because with a high degree of probability you will get blue-cream cats, which are not in demand. If you breed with a cream cat, the kittens will be black and cream.
7. Is it possible to match a British woman with a Scottish man if they are brother and sister?
Answer: brother and sister are close relatives. When mating, such parents may have offspring with serious developmental defects, including stillborn kittens. There are such defects as cleft palate, cleft lip, polydactyly, etc. These kittens need to be euthanized. It is unlikely that you will consciously want to undertake such an experiment. In addition, a British woman and a Scotsman cannot be brother and sister - they are different breeds. You probably meant the Scottish Fold (loose-eared Scots) cat and the Scottish Straight (straight-eared) cat.
8. I have a British blue cat. He has a pedigree, but has never attended exhibitions and has no titles. The breeder, when she sold him to us, tearfully asked him not to be neutered, and said that he would be an excellent sire. He is already 4 years old, about 2 years ago they brought him a cat, but nothing worked out. Please tell me where we can give information that we want to breed him? And how is this done?
Answer: In order for matings to be official, the cat must receive a certificate confirming its breeding status. Having a pedigree is not enough. You need to exhibit a cat at two different exhibitions, and it must receive scores of at least “excellent” from three judges. When the cat has a document allowing him to participate in further breeding, only then can he begin to compete for cats. But keep in mind that no one is obliged to provide you with cats. The cat is chosen by the cat's owners and the choice is free. Your cat should please both cat owners and the cats themselves. This will require a show career.
9. There was already a question about parents and relatives. For us this is already a fait accompli. A month ago we bought a British kitten, and only today we got a pedigree done. It turned out that the kitten’s maternal parents were brother and sister. Our cat is already 3 months old. Healthy, cheerful, can we be afraid of anything?
Answer: with inbreeding, magnificent kittens are sometimes born, better than with parents who are distant in blood. Culling also happens, but this is immediately visible: cleft palate, cleft lip, polydactyly, etc. If everything is fine with the kitten now, then you will need to make sure that during further matings the cats have fresh blood (to exclude further inbreeding). If you are planning castration, then there should be no problems.
10. Thanks to you, I bought a British cat in January. Very happy, thank you very much!!! At first I thought that I would sterilize my pussy, but now I want my Buska to have kittens. Please tell me at what age is it better to breed a cat to have healthy offspring? Do you need to go to the exhibition before then?
Answer: I’m happy for you and your Buska. It is best to skip the first two heats and breed on the third. Just don't give any hormonal drugs. Usually cats are bred after a year, when they are fully mature and strong. I wish you success!
11. The cat is 3 years old, documents and pedigree are available, at the age of 3 months. At the “Eurasia” exhibition he took 1st place, but after that he was not exhibited. Is it possible to breed him with a cat through a club or in another way without going through an exhibition? Breed: BRI, color blue.
Answer: in order to officially breed a cat, you must have a quality certificate confirming its breeding status. To do this, the cat must be assessed by three judges at two shows and receive the title of breed champion. But this is not enough. It is necessary that cat owners like the cat, since cats have the right to choose the groom.
12. I have a Scottish fold cat, he is 4 years old and there were only 2 cats: the first cat was operated on and did not become pregnant (although mating occurred), and the second cat I still did not understand whether there was mating or not, because I saw that he was jumping on top of her, but at the same time both were silent, then the owner of the second cat moved out, and I don’t know anything more about her. Both matings were free. Now I decided to do paid knitting, they brought it british cat(not untied), for the first time I thought the mating had taken place, but recently they brought it to me. The second time, he doesn’t let the cat come to him and tucks his tail under him, lies down awkwardly, so that the cat can’t do “his job.” We entered into an agreement, there is a clause: if the cat does not conceive, then the second time is free. What to do if nothing happens the second time??? I think that mating with this aggressive cat will not work the second time.
Answer: If the cat is not untied, then there may be problems. After two years, as a rule, rare cats can untie the cat. She is already considered an “old maid”. This is not an aggressive cat, but an inexperienced cat, or the cat is not in heat. Most likely, the mating did not take place the first time with this cat either. It happens that for the first time a cat is so lethargic from shock that the cat can even perch on her, but nothing will work, because... she’s not in good shape - she’s just lying there,
like a rag. If the cat cannot untie it the second time, then you must return the money, since you do not have documentary evidence that the mating took place - video filming. When mating is paid, it is advisable to present video materials so that the owner has no doubts. When the cat is honest
worked - and this is confirmed, then the remaining problems are cat problems. There are some cats that are infertile. Sometimes the cat's owner is to blame if she brought her in late and missed estrus.
By law, you can breed your Fold cat only with Straight cats (Scottish Straight), and then only if he has a certificate confirming his right to breed.
This article is addressed to those cat lovers and owners of catteries, as well as the chairmen of those clubs and associations whose main goal is to consolidate and improve the pedigree qualities of their animals through purebred breeding and selection (selection). Let us immediately emphasize that since selection involves strict culling, this goal comes into conflict with commercial cat breeding, where the main goal is profit.
Inbreeding as a component of purebred breeding. In the course of his work, the breeder must decide which females should be mated with which selected males so that their offspring will combine certain characteristics and acquire improved traits. This selection event is called selection of pairs for crossings. The selection of pairs should be carried out systematically and systematically, and its goal is to change the genetic structure of the animal population of a given nursery in the desired direction or to preserve and consolidate a certain combination of valuable traits in the offspring. Sometimes, to breed new breeds or introduce completely new characteristics into a breed that were previously not characteristic of it, interbreeding or even interspecific crossing is used, but usually the main direction of the breeder’s work is the so-called purebred breeding - mating of individuals of the same breed.
Purebred breeding is divided into two types: outbreeding - a system of unrelated matings of animals within a breed, and inbreeding - a system of matings of individuals having a close degree of relationship, such as brother-sister, father-daughter, mother-son, cousins, etc. . In general, inbreeding assumes that the mated individuals - the future father and mother - have common ancestors or at least one common ancestor. Although for specialists the importance and necessity of inbreeding in purebred breeding is obvious, among amateurs there are a lot of myths and prejudices, both against inbreeding itself and against the use of inbred sires in breeding. (We will say in advance that the latter is a particularly big mistake, since inbred selective sires are, as a rule, prepotent - their children turn out to be basically “like their father” - and also often produce exceptionally strong offspring.)
Genetic basis of inbreeding. What is the biological (genetic) essence of inbreeding? All modern breeds of animals, including cats, are heterozygous for many genes. This means the following. The zygote - a fertilized egg - receives one from both the father and mother full set genes, so it has a double set of them. If both genes responsible for a given trait - one from the father and the other from the mother - are identical, then this condition is called homozygous for this gene, and an individual homozygous for this gene will develop from the egg. If the genes of the equivalent pair, for example, those determining the formation of black hair pigment, are different (say, the father passed on the black color gene C, and the mother passed on a modified, for example, Himalayan, cs gene), then the individual will turn out to be heterozygous for this gene (Ccs). In the latter case, the black color gene is dominant, and the animal will be externally (phenotypically) black, but will be a carrier of the recessive (hidden) Himalayan gene. If such a heterozygous animal - let it be a black cat, a carrier of the Himalayan gene - is crossed with its sister, also a black cat, carrying a hidden Himalayan gene, then a split will be observed in the offspring (Fig. 1): part of the offspring will be black in color (CC - homozygous , and Cсs are heterozygous genotypes), and the other part is Himalayan (Сссs homozygous genotype). This happens because when crossing this black cat with his black sister, their gamete sex cells (sperm and egg) - carrying a single set of genes, will occur in all four possible combinations: C from cat and C from cat, C from cat and cs from cat, cs from cat and C from cat, cs from cat and cs from cat. Therefore, with a probability of 1/4, two Himalayan genes (one from the father, the other from the mother) will converge in one zygote and give a homozygous Himalayan genotype and, therefore, a Himalayan phenotype in some kittens of the litter. The other part of the litter, with the same probability of 1/4, will be homozygous for the solid black gene (CC). Thus, the genetic essence of inbreeding comes down to the process of decomposition of a population into lines with different homozygous genotypes. Since during inbreeding, genes that were in a heterozygous state pass into a homozygous state; in the next generation, when crossing homozygous animals of the same color, no splitting will be observed. In this way, with the help of inbreeding, identification is carried out hidden signs, consolidation of desirable characteristics in generations and the creation of stable genetic lines.
The fastest practical way to increase homozygosity in higher animals is to mate siblings who have the same father and mother (it makes no difference whether the sibs are taken from littermates or from different litters), as well as to mate father and daughter or mother to son.
Sometimes the opinion expressed among non-professionals that, they say, it is possible to mate a father with a daughter, but not a mother with a son, is a myth that has no basis; the effect of both types of inbreeding is exactly the same. If such close inbreeding (incest) is carried out for 16 generations in a row, then 98% homozygosity for all genes is achieved, and therefore, due to the absence of segregation, all individuals of these litters become almost identical in genotype and phenotype - all children are identical, like twins, Of course , in practice, a much smaller degree of inbreeding is usually used, and accordingly a much lower degree of homozygosity is achieved.
It should be noted that the mating of second cousins (common great-grandfather) leads to an increase in homozygosity by only 2% over an infinite number of generations. Consequently, inbreeding of this type is already fundamentally different from closer degrees of inbreeding and essentially does not lead to the achievement of the goals that are placed before the system of consanguineous matings. Breeders who, for one reason or another, avoid inbreeding may not be afraid to mate second cousins.
Determining the degree of inbreeding and the inbreeding coefficient in cats. Based on the analysis of the animal's pedigree, it is possible to qualitatively assess the degree of inbreeding, which is expressed by the saturation of the pedigree with common ancestors (nicknames) on the maternal and paternal lines. According to Shaporouge, Roman numerals denote generations (a series of ancestors), counting the parent as the first, grandfather as the second, etc. If a common ancestor is repeated in both the maternal and paternal parts of the pedigree, then its occurrence in the maternal pedigree is indicated first, and then, after a dash, in the paternal pedigree. Then the crossing son x mother will be designated as I-II (Fig. 2, a), father x daughter as II-I (Fig. 2,6), brother x sister as II-II (Fig. 2, c, d) , grandfather x granddaughter as III-I (Fig. 2, e), cousins x sister as IIIIII (Fig. 2, f), etc. Inbreeding type father x daughter (II-I), son x mother ( I-II) and brother x sister (II-II) is designated as very close, or incest; inbreeding type II-III or III-II is close inbreeding; and crossing III-IV, IV-III, IV-IV, II-V, etc., is moderate inbreeding. Due to the lack of perceptible effects, more distant inbreeding may in practice not be considered true inbreeding. Owners of high-quality purebred cats, having picked up the cat's pedigree, can themselves assess how often and to what extent inbreeding was used by the breeders who participated in the breeding of this pet.
To quantitatively take into account the degree of inbreeding in the pedigree of an animal and thereby determine the measure of its homozygosity, the English geneticist S. Wright introduced the concept of inbreeding coefficient (F). This coefficient is calculated as follows. First, the number of generations (arrow - such as in Fig. 2) is calculated from the common ancestor A of the father and mother to the father of a given animal (p), then the number of generations (arrow) from the same ancestor A to the mother (t). These numbers are summed up, and one is added to the sum: n = p+ m+ 1. The inbreeding coefficient of the analyzed animal (proband X) for this ancestor is equal to 1/2 to the power of n: Ga = (1/2)n. If the father and mother have several common ancestors, then the coefficients are summed up: Fx =EF, =E(1/2)n, where i are the common ancestors A, B, C, etc.
As an example, let’s calculate the inbreeding coefficient of an animal (proband X) obtained from crossing siblings (II-II, Fig. 2c). In the pedigree, the distance (path) from grandfather to father is 1 generation, from grandfather to mother - 1 generation, therefore, n = 1 + 1 + 1 = 3, which means Fв = (1/2)3 = 1/8. But they have one more common ancestor - their grandmother; from her to her father - 1 generation, from her to her mother - 1 generation, and therefore Fa will also be 1/8. The overall inbreeding coefficient for X is Fx = Fa+ Fb = 1/8+ 1/8 = 1/4, or 0.25.
Another example is the crossing of a grandfather with a granddaughter (III-I, Fig. 2,e). Here the offspring on the paternal line have no generations (arrows), i.e. 0 generations, on the maternal side - 2 generations, whence n = 0 + 2 + 1 = 3, and then Fx = (1/2)3 = 1/8, or 0.125.
Finally, an example with crossing cousins with sister (III-III, Fig. 2, f). The common ancestors of their offspring are great-grandfather and great-grandmother. From great-grandfather to father - 2 generations, from him to mother 2 generations, i.e. n = 2 + 2 + 1 = 5, and accordingly Fb = (1/2)" 1/32. The same is obtained when calculating the inbreeding coefficient for another common ancestor - great-grandmother: Fa = (1/2)3 = 1/32 Therefore, the total inbreeding coefficient Fx = Fa + Fb = 1/32 + 1/32 = 1/16, or 0.0625.
From available pedigrees, each breeder or owner of a purebred animal can calculate the inbreeding coefficient of their pets or their parents and grandparents - if inbreeding was used in their production. As already mentioned, this coefficient is an indicator of the degree of purity (homozygosity) of the lines participating in the pedigree, as well as an indication of the possible prepotency of the corresponding sires and/or female sires (see below). The higher the inbreeding coefficient of an animal, the more of its genes are in a homozygous state. Naturally, as follows from the formula, the inbreeding coefficient cannot exceed one.
Inbreeding depression and heterosis. Why is it that in human society, in most civilizations, there is either a direct ban on incest or condemnation of it? Moreover, why in the wild is everything adapted in such a way as to avoid inbreeding and homozygosity as much as possible? The main reason is that both wildlife and human society require a variety of genotypes and individuals in the population to successfully survive and adapt to changing environmental conditions (including social and economic conditions in the case of human society). In a diverse community there will always be individuals best adapted to a given specific situation; however, the situation is changing - and other individuals, with other signs, float to the surface. The uniformity of a population, although well adapted to the given specific conditions of its existence, dooms a biological species to extinction when conditions of existence change. Thus, the desire to create diversity is necessary not for individual individuals, but for the entire species to meet the various and changing demands of the environment and the historical process .
But there is also a direct danger of inbreeding for individual individuals. The fact is that both during the individual life of an animal (and a person), and over generations, mutations—gene changes—occur from time to time. Most mutations are harmful, and if they immediately manifested themselves, they would lead to death (lethal mutations), deformities, abnormal behavior, inconsistencies environment, and so on. However most of mutations at the same time have a recessive nature, i.e. in combination with a normal paired gene, due to the double set of genes, does not appear in the heterozygous state. The burden of such harmful, but not manifested, hidden mutations is present in every heterozygous individual, including every person. Inbreeding creates homozygosity, including homozygosity for harmful genes, and, consequently, leads to their phenotypic manifestation in the offspring - intrauterine or early death, deformities , reduced viability, etc. This phenomenon is called inbreeding depression.
Let's ask the opposite question - why, despite the danger of inbreeding depression, do breeders who breed and improve domestic animals so often resort to inbreeding and are not afraid of it? The answer is simple: breeders do not strive to ensure maximum survival, vitality and high qualities of all offspring, but select the best, culling (for example, castrating) defective, weak and simply undesirable traits. Thus, during inbreeding, when the genotype is decomposed into homozygous lines, harmful recessive genes appear and are removed from further breeding, and all “good” genes and their combinations are fixed in a homozygous state and left for further generations. Thus, inbreeding in the hands of a breeder is a way of removing the load of harmful mutations from the genotype, on the one hand, and creating the necessary combinations of valuable genes and traits, on the other. In addition, thanks to homozygosity, the homogeneity necessary for breeding any new breed is created, meeting the requirements of this breed, and the corresponding valuable traits are fixed in the offspring. It should be noted that as inbreeding and selection of the best, due to getting rid of the burden of harmful hidden mutations, the danger of inbreeding depression during inbreeding of selected inbred animals decreases.
When crossing between representatives of different independent inbred lines, a phenomenon can be observed that, in a certain sense, is the opposite of inbreeding depression - heterosis, also called “hybrid vigor”. Such hybrids of two inbred animals usually show increased vitality, growth, fertility, etc. This occurs because when crossing between two inbred lines selected and therefore similar in typical characteristics of the breed, homozygosity for these selected characteristics is preserved in the offspring, whereas the remaining harmful mutations that are not rejected are transferred to a heterozygous state and thereby become recessive, i.e. do not appear.
Practice the goals of inbreeding cats. Let us consider in general and summarize the tasks that are performed and the goals that are pursued by livestock breeders, including cat breeders, when using inbreeding.
Firstly, inbreeding is necessary when developing a new breed or new group within the breed. To increase genetic diversity and attract new traits, the breeder crosses animals of different breeds. The resulting hybrid offspring is heterozygous and will therefore produce segregation in subsequent generations. To consolidate the desired combinations of traits, inbreeding is mainly used close, such as brother x sister, father x daughter and mother x son. As a result of inbreeding, homogeneous families are created and a constant manifestation of traits is achieved. Among inbred offspring, up to 80% of the inbred offspring are strictly culled - defective, weak and not meeting the intended standards.
In Fig. Figure 3 shows an example of very close inbreeding when breeding Himalayan cats with lilac markings (lilac point) in the English Mingchew cattery. A cat with a chocolate-point color - Snuff - was obtained by crossing a Tromo cat, with a seal-point color, a carrier of the chocolate and blue genes, from the American nursery Briery, with a Siamese cat Trayvia, also a seal-point and also a carrier of the chocolate and blue genes, from cattery Mingchshch, This chocolate-point cat (Snuff) was bred with her father, the cat Tromo. The cat Chock, a seal-point, born from them was bred with his mother, the cat Snuff, a chocolate-point. From them the first cat with lilac markings (lilac point) was born - Sulatri. It is worth noting the very high inbreeding coefficient of Sulatri: P 3/8, or 0.375, i.e. higher than when crossing siblings.
Secondly, close (very close) inbreeding is used in cases where it is necessary to identify producers who are carriers of lethal, semi-lethal and other undesirable genes. This is the so-called test inbreeding. Based on the results of test inbreeding, various decisions can be made: either such sires are discarded or used to produce homozygous offspring (through inbreeding) with the culling of defective ones and the selection of the best ones, thereby achieving purification of the genotype from unwanted genes.
Thirdly, the purpose of inbreeding may be to breed a highly potent producer, that is, one that effectively passes on its traits to children. It is known that inbred animals have a higher individual prepotency compared to individuals obtained from unrelated crosses. Because of this, it is a widely accepted practice in animal husbandry to mate an inbred male with a non-inbred female; This practice is called top crossing. It is important that a good inbred producer, passing on his selected qualities to his descendants, can significantly improve the nursery stock and give it its own face, its own peculiarity, its own type.
Fourthly, sometimes breeders create inbred lines in their nurseries, so that later, by crossing representatives of different lines (often this is done in cooperation between different nurseries), they can obtain the effect of heterosis - powerful, large, resilient and fertile offspring.
In conclusion, we would like to emphasize that in order to conduct breeding work - including with cats - it is necessary to use systems of competent selection and selection of animals. In this case, selection is distinguished by phenotype and by genotype. Cat lovers are well acquainted with cat shows of various levels, where class assessment (in professional language - grading) of cats is carried out. This is an assessment based on phenotype. Assessment by genotype should be carried out based on the pedigrees of animals and the quality of their offspring. Generally speaking, the breeding value of an animal can be determined only by evaluating the sire by the quality of his offspring. An animal of excellent phenotype will not always be good manufacturer. Livestock farmers have popular expression: “A good bull is worth half a herd.” The same is with stud cats: the quality of the cattery and its personality is largely determined by the stud cat (or stud cats, if there is more than one). Such a stud cat must be highly prepotent, and therefore breeders should turn their attention to inbred studs. Moreover, you cannot create a good nursery by simply purchasing expensive animals with champion and grand champion titles abroad. It is necessary that in the nursery itself and from the nursery producers on the side, animals of the international champion and grand champion level are born. And this requires competent breeding work, in which inbreeding plays a significant role.
The breeder always faces two main tasks: to improve certain breed characteristics of his animals and to achieve stable transmission of these characteristics from generation to generation. At different stages of development of the breed, and indeed of the nursery itself, first one or another task comes to the fore, but in terms of their importance they are equal. The stability of the transmission of traits requires the creation of stable, non-splitting gene complexes, that is, a predominantly homozygous state of the alleles included in them. And such homozygosity can be achieved only by using closely related matings - inbreeding.
But what type of inbreeding to choose, what degree of inbreeding to focus on - this question must be decided by the breeder depending on the animals available in the nursery, on their breed qualities and genetic potential, and based on the task at hand: for example, to quickly consolidate a valuable trait or a rare one color, achieve uniformity of offspring in a number of indicators, etc.
Purebred breeding is divided into two types: OUTBRIDING - a system of unrelated matings of animals within a breed, and INBRIDING - a system of matings of individuals having a close degree of relationship, such as brother-sister, father-daughter, mother-son, cousins, etc. . In general, inbreeding assumes that the mated individuals - the future father and mother - have common ancestors or at least one common ancestor. Although for specialists the importance and necessity of inbreeding in purebred breeding is obvious, among amateurs there are a lot of myths and prejudices, both against inbreeding itself and against the use of inbred sires in breeding. The latter is a particularly big mistake, since inbred selective sires are, as a rule, prepotent - their children turn out to be mostly like their father - and also often produce exceptionally strong offspring.
Mating of second cousins (common great-grandfather) leads to an increase in homozygosity of only 2% over an infinite number of generations. Consequently, inbreeding of this type is already fundamentally different from closer degrees of inbreeding and, in fact, does not lead to the achievement of the goals that are set for the system of related matings.
Method for determining inbreeding
The most accessible method for determining animal inbreeding was proposed by A. Shaporuzh. Using his method, it is possible to determine which rows have a common ancestor.
The first row is taken to be father and mother,
for the second - grandfathers and grandmothers,
for the third - great-grandfathers and great-grandmothers, etc.
The entry is made in Roman numerals, the first digit indicating the row in which there is a common ancestor on the paternal side of the pedigree and after the dash the row in which the common ancestor on the maternal side is found. If the rows of ancestors repeated in the pedigree are found in any one, paternal or maternal side of the pedigree, then the numbers are separated by commas.
Degrees of inbreeding (according to A. Shaporuz’s classification):
1. Close inbreeding: they knit animals that are very closely related.
Father and daughter (II – I)
Mother and son (I – II)
Siblings (II – II)
2. Close inbreeding: mating of animals in which the same ancestor is at the forefront of the pedigree.
Granddaughter and grandfather (III-I)
Grandmother with grandson (I-III)
Incomplete brother and sister (II-II)
Nephew with Aunt (III-II)
Niece and Uncle (II-III)
3. Moderate inbreeding– carried out in the following degrees III-III, III-IV, IV-III, IV-IV.
4. Distant inbreeding– when the common ancestor occurs in generations V-V, IV-V, V-IV, III-V, V-III. If the common ancestor occurs beyond the fifth generation, the animals are considered practically unrelated.
5. Inbreeding, in which there is a pair or several common ancestors in the pedigree of the offspring is called complex.
Types of inbreeding and purposes of its use:
1. Close inbreeding (father x daughter; mother x son) - can be necessary when laying down lines, for consolidating and “fixing” the genes of an outstanding ancestor. In some cases, having animals that are unique in their value and for which it is impossible to find worthy partners, they are forced to mate them with close relatives in order to preserve their genotype and the valuable traits that this type possesses.
This need arises at the initial stages of breeding new breeds, and also sometimes in cases of line breeding, when they strive to obtain something new through purebred breeding, without resorting to the use of animals of other breeds.
Close inbreeding is also used to test a separate line or specific producers for carriage of hereditary anomalies. Close and close inbreeding is not recommended to be used constantly on the same
same animals, since inbreeding has the strongest effect on those characteristics that are associated with reproductive abilities, reproductive function and vitality. It should be noted that these traits are weakly inherited, so it is advisable to mate inbred animals with animals of other lines or carry out “blood refreshment”, and then select a pair taking into account moderate inbreeding.
Backcross a representative of each generation is first crossed with one of the parents, and then with one of the descendants obtained from the previous crossing.
Sibcross In every generation, brother and sister interbreed. Both of these methods are aimed primarily at consolidating the properties of the ancestral pair of cats. To carry out such crosses, both ancestors must not only possess those wonderful qualities that were described above, but also produce homogeneous offspring.
2. Moderate inbreeding used to consolidate the heredity of outstanding animals. The common ancestor occurs in the third and fourth generations. For example, with the 1V-1V variant, homozygosity increases by only 0.78% and, of course, this cannot have any noticeable effect on the phenotype and genotype. Distant inbreeding has little effect on increasing the homozygosity of offspring and is not much different from unrelated mating (outbreeding).
The most common irregular breeding systems are linear and the so-called “closed”.
Linear - Linear breeding, or linebreeding, is breeding along the lines of certain sires, which are repeated in the pedigree through 2-3 generations (mating a half-brother with a half-sister or cousins). Sometimes this method gives stable results.
Closed- used in combination with careful selection of manufacturers. With such a system, a “closed nursery” simultaneously contains 1-3 stud cats and a certain number of females - from 3 to 10. The best representatives are selected from the offspring of the initial pairs, the worst of the parents are discarded, replaced by the best of the offspring, and pairs of the second stage are formed. With each new generation, these operations are repeated, and animals from other nurseries are not used for breeding, and the number of males and females used as breeders remains unchanged
The system of improving matings is used in cases where the nursery initially contains 2-4 mediocre females and one high-quality sire. First stage of this system (groeding) is similar to backcrossing - the best daughters are selected from the offspring obtained from these pairs and mated with the father. However, unlike the backcross system, in the next generation the best females are again selected and mated again with the same sire. At the next stage (upgrading) - a male is selected from the descendants, superior in its qualities to the first, and he is mated according to the same scheme. The requirements for the improver are the same as for the ancestor of the line, plus inbred origin is desirable.
Advantages of inbreeding:
1. Increases the number of homozygous individuals;
2. Quickly identifies the main defects, which makes it possible to eliminate those carrying recessive defects from breeding;
3. Stabilizes genetic potential and quality model;
4. Makes it possible to more accurately predict the quality of future offspring.
Disadvantages of inbreeding:
1. The slightest error (undesirable trait) is amplified due to homozygosity and is fixed in a given breed group;
2. Excessive inbreeding weakens physical characteristics and conformation, and also negatively affects the reproductive function and viability of animals;
3. Does not enrich the initial genotype of the population.
Conclusion
The use of inbreeding is aimed at consolidating in the pedigree the desirable genetic inclinations of the ancestor on whom inbreeding is carried out. Inbreeding can have a positive impact on the result of breeding work only with the strictest selection, that is, with methodical culling. Systematic inbreeding includes a well-thought-out mating plan, combining degrees of inbreeding and using interline crosses, with the selection of the best and healthiest animals that are similar in breed type. The producers used, as already mentioned, must be in good health, free from defects and not be carriers of genetic abnormalities. Moreover, inbreeding should alternate with regular refreshment of the line, through the influx of new blood and the use of outbreeding with animals of the same type. To conduct breeding work - including with cats - it is necessary to use systems of competent selection and selection of animals. In this case, selection is distinguished by phenotype and by genotype. Cat lovers are well acquainted with cat shows of various levels, where class assessment (in professional language - grading) of cats is carried out. This is an assessment based on phenotype. Assessment by genotype should be carried out based on the pedigrees of animals and the quality of their offspring. Generally speaking, the breeding value of an animal can be determined only by evaluating the sire by the quality of his offspring. An animal of excellent phenotype will not always be a good producer. Livestock breeders have a catchphrase: “A good bull is worth half a herd.” The same is with stud cats: the quality of the cattery and its personality is largely determined by the stud cat (or stud cats, if there is more than one). Such a stud cat must be highly prepotent, and therefore breeders should turn their attention to inbred studs. Moreover, you cannot create a good nursery by simply purchasing expensive animals with champion and grand champion titles abroad
It is necessary that in the nursery itself and from the nursery producers on the side, animals of the international champion and grand champion level are born. And this requires competent breeding work, in which inbreeding plays a significant role.
By Dr. Heather E. Lorimer, Assistant Professor, Genetics Department of Biological Sciences Youngstown State University
Inbreeding- This is inbreeding, that is, obtaining offspring from parents who are closely related. For example, from mother and son, father and daughter, uncle and niece, aunt and nephew, cousins, grandfather and granddaughter, grandmother and grandson.
All cat breeders know the dangers of inbreeding. Everyone has heard (and many have seen) the tragic consequences of doubling recessive genes. One way to avoid the manifestation of lethal recessive genes is outcrossing. This is the selection of such parents with characteristics that you want to fix so that they are not relatives, at least in the third or fourth generation. However, it must be taken into account that the breed line used for outcrossing may carry exactly those genes that need to be excluded.
However, it is quite possible to weed out genetic defects even in the most inbred cat breed lines. Scientists do this all the time in their research - the strains of mice, rats and other animals used are so inbred that they are almost genetically identical. Each animal in these strains will be an identical twin (except for gender) to every other animal in that strain. Moreover, the animals do not carry lethal genes and are completely healthy. The only thing that spoils the picture is that they need to be kept in almost sterile conditions, since their immune system is not able to fight the usual range of diseases.
The immune system of a cat, like that of all animals, is extremely dependent on genetic diversity. There are two main types of immune reactions:
- B cells, which produce antibodies that neutralize or kill foreign particles (such as bacteria or viruses) that enter the body.
- Reaction provided by action T cells, which destroy dangerous cells - tumor cells and those infected with a virus.
These reactions are similar in many ways. The cells involved are very specific - each type produces only one type of antibody or is capable of recognizing and killing only one type of dangerous cell. The most amazing thing is that for every type of infection or tumor that can threaten an animal, there is already a cell in the body specific to this infection or tumor.
This means that all cats have millions of genes, each of which is coded to produce a specific antigen or cell with a specific receptor. The problem is that there is not enough room on the chromosomes for all these genes. To get around this problem, the body uses a very elegant solution: immune system cells do not have the full set of genes to produce antigens. Instead, they have a collection of small gene segments that divide and combine to assemble a specific gene. Only cells of the immune system can change their own DNA. If this happens in any other cells, it is very dangerous. For immune system genes, however, this ability is very important - otherwise the body would not be able to fight very many diseases.
To understand the dangers of cat inbreeding in terms of loss of immunity, imagine the original (germline) DNA with six segments. Let each segment contain a different set of elements (in reality there are many more). Such a six-segment array has the potential to produce 10x10x10x10x10x10 = 1 million different antibodies.
If the chromosomes of a cat's (or any other animal's) parents have the same set of immune system gene segments, this means the kitten will lose half of its potential antibody genes. With subsequent inbreeding, the next part of the gene segments will be lost. This genetic phenomenon is called " Crossover"At the same time, each lost segment causes a loss of the ability to produce thousands of different antibodies.
In our example, the immune system of a kitten from two completely non-imbred parents, having a different set of chromosomes, will be able to produce two million different antibodies. Each of them will be specific to a certain type of infection. The body of a kitten from parents with identical immune system chromosomes (homozygous) will be able to produce only one million different antibodies. In our example, the loss of just one segment in a crossover would cause the loss of one hundred thousand antibodies, so the immune system would only be able to produce 900,000 antigens. When this happens, the cat loses the ability to resist certain diseases. If a number of kittens lose the same gene segments, as happens in inbred lines, entire catteries or purebred lines may be lost to infections that usually have little effect on the health of normal cats.
A well-known example of such disease sensitivity caused by a lack of genetic diversity is the problems in wild and captive cheetah populations. Captive breeding programs for cheetahs suffer from low level fertility and high infant mortality. In addition to being highly susceptible to injury, cheetahs have been shown to be highly susceptible to Feline Infectious Peritonitis (FIP). Most cats exposed to this virus also become infected, but less than 10% develop the fatal disease. However, among cheetahs exposed to the virus, mortality rates reach 50%. Stephen J, O'Brien and his colleagues, having studied this problem, published their findings in the journal Scientific American (May, 1986). They found that cheetahs are very close genetically. Moreover, so much so that cheetahs born thousands of miles away from each other, skin grafts were not rejected from each other (which is usually only possible for identical twins). At some point in history, the cheetah population declined so much that their immunological diversity as a species was lost. As a result, these big, beautiful cats are in danger of extinction.
One of the most important tasks of cat breeding is to protect our wonderful companions from such danger. It is vitally important to avoid “fixing” insufficient immunological diversity while trying to fix the desired features. Fortunately, this is not difficult at all. When trying to consolidate some trait in a cat breed, such as size or set of ears, it is necessary to use several breed lines for selection. With outcrossing, there is no loss of type if the cat that is used for outcrossing lacks the necessary traits.
It is very important to monitor the appearance signs of excessive inbreeding:
- Low birth rate (from males and females).
- Regular small number of kittens (1-2) per litter.
- Asymmetry, curvature of the jaws, fractures of the nose, incorrect placement of the eyes.
- Regular occurrence of cancer in young cats.
- Relatively high level mortality from one disease. If 50% of kittens from a litter or adult cats in a cattery die from a simple infection, this is a clear sign of insufficient immunological diversity in the breeding line.
Each breeder, working with a breed, must decide which cats and males need to be selected for mating so that the resulting offspring have certain characteristics. This process is called selecting pairs for crosses.
Purebred breeding is divided into two types: outcrossing- a system of unrelated matings of animals within a breed, and inbreeding— mating of related animals with each other to consolidate valuable characteristics of the breed.
What is the genetic essence of inbreeding?
All modern cat breeds are heterozygous for many genes. This means the following. The zygote - a fertilized egg - receives one complete set of genes from both the father and the mother, so that it has a double set of them.
If both genes responsible for a given trait - one from the father and the other from the mother - are identical, then this condition is called homozygous for this gene, and an individual homozygous for this gene will develop from the egg. If the genes of the equivalent pair, for example, those determining the formation of black hair pigment, are different (say, the father passed on the black color gene C, and the mother passed on a modified, for example, Himalayan, cs gene), then the individual will turn out to be heterozygous for this gene (Ccs).
In the latter case, the black color gene is dominant, and the animal will be externally (phenotypically) black, but will be a carrier of the recessive (hidden) Himalayan gene. If such a heterozygous animal - let it be a black cat, a carrier of the Himalayan gene - is crossed with its own sister, also a black cat, carrying a hidden Himalayan gene, then splitting will be observed in the offspring: part of the offspring will be black in color (CC - homozygous, and Ccs - heterozygous genotypes), and the other part is Himalayan (сссs homozygous genotype). This happens because when crossing this black cat with his black sister, their gamete sex cells (sperm and egg) - carrying a single set of genes, will be found in all four possible combinations: C from cat and C from cat, C from cat and cs from cat, cs from cat and C from cat, cs from cat and cs from cat.
Therefore, with a probability of 1/4, two Himalayan genes (one from the father, the other from the mother) will converge in one zygote and give a homozygous Himalayan genotype and, therefore, a Himalayan phenotype in some kittens of the litter. The other part of the litter, with the same probability of 1/4, will be homozygous for the solid black gene (CC).
Thus, the genetic essence of inbreeding comes down to the process of decomposition of a population into lines with different homozygous genotypes. Since during inbreeding, genes that were in a heterozygous state pass into a homozygous state, in the next generation, when crossing homozygous animals of the same color, no splitting will be observed.
In this way, with the help of inbreeding, hidden traits are identified, desired traits are consolidated in generations, and stable genetic lines are created.
But you need to understand that the consolidation of any characteristics is not an automatic consequence of inbreeding. Obtaining high-quality animals through inbreeding is, first of all, a competent policy of the breeder, who, along with inbreeding, also selects the right pairs.
Based on an analysis of the animal's pedigree, it is possible to qualitatively assess the degree of inbreeding, which is expressed by the presence of common ancestors on the maternal and paternal lines. Inbreeding is recorded using Roman numerals that correspond to the ranks of the ancestors. The count starts from the parent, i.e. I - parents, II - grandfathers, III - great-grandfathers, IV - great-great-grandfathers, etc. If a common ancestor is repeated in both the maternal and paternal parts of the pedigree, then its occurrence in the maternal pedigree is indicated first, and then, after a dash, in the paternal pedigree.
Son-mother will be recorded I-II, daughter-father II-I, sister-brother II-II. This is close inbreeding. Such inbreeding is used in cases where it is necessary to identify producers who are carriers of lethal, semi-lethal and other undesirable genes. Such a check must be arranged for those producers on whom we plan to inbreed animals in our nursery in the future.
Grandmother-grandson will be recorded I-III, granddaughter-grandfather III-I. This degree of inbreeding is considered close.
Cousins III-III. This is moderate inbreeding. As well as III-IV, IV-III, IV-IV.
Distant degree of inbreeding IV-V, V-IV, V-V.
This system for recording the degree of inbreeding is considered universal and very convenient. There is no need to explain to another breeder by nickname who is related to whom in the pedigree of your animal, and is also very convenient when drawing up a long-term breeding program.
Inbreeding is a very powerful weapon in the hands of the breeder. But he also has another side. Inbreeding creates homozygosity not only for the genes we need. Harmful genes responsible for genetic abnormalities, hereditary diseases, and deformities can also become homozygous.
Using inbreeding in a breeding program is a very serious decision. Breeders who strive to receive so-called “easy money” from sales as much as possible more kittens will never put inbreeding into practice.