I.V. SHUSTROVA CATS. GENETICS AND BREEDING BREEDING.
BREEDING AND SELECTION.
Every planned breeding of purebred animals begins with the selection of potential producers. As a rule, the main guideline in relation to the suitability of animals for breeding for breeders is the expert assessment at the exhibition. However, the selection only on the basis of expert evaluation has several serious shortcomings. First of all, the assessment obtained by the cat at the exhibition is complex, that is, it takes into account all the parameters of the breed. At the same time, the expert does not always take into account the real state, the features and the number of the breeding population of this breed, with which the breeder or the felinologist of the club must work. The second minus is the inevitable subjectivity of the judges, who in their assessment are guided not only by the requirements of the standard, but unconsciously amends the livestock level that exists in the felinological organizations of their countries.
And, finally, the third drawback of expert evaluation is the impossibility to adequately assess the divorcing potential of representatives of the breeds that are in the experimental breeding stage, even with a preliminary standard. In most cases, the results of such selection are lower than expected, because they do not take into account animal health, carrier of recessively inherited diseases and anomalies, and it is also impossible to fully control individual characteristics of the exterior.
For the purposes of such control, the so-called tandem selection is sometimes used, in which the breeding process is initially aimed at achieving full compliance with the standard 1-2 significant characteristics. The process of the formation of each next breed trait begins only after the first selected characteristics have reached the required level – of course, for the entire livestock used in the work. The main advantage of this method is the ability to quickly improve individual signs. But its main danger is that the progress achieved in the early stages of breeding will soon be lost in the transition to work on the following characteristics.
Another partially used method of selection is the so-called independent selection, that is, the exclusion from breeding of those individuals whose performance does not meet the requirements of at least one characteristic. Of course, the use of this method in full is almost impossible. For this, it is necessary to have an already established stable group of pedigree animals, which, of course, is ideal conditions. But almost any breed standard provides for flaws that are disqualifying, that is, automatically excluding the possibility of animal breeding. The advantage of this method is that it provides control over several characteristics simultaneously.
A peculiar combination of the advantages of these methods is the use of breeding indices. When using this method, each breeder of interest at this stage of the work characterizes the exterior of a particular cat in relation to the requirements of the standard on any convenient scale, 5 or 10-point. The number of estimated characteristics is generally unlimited. Different characteristics (stats) of an animal have different “weight”, that is, a numerical coefficient that shows the degree of importance of the analyzed qualities. Odds are also set on any convenient scale (of course, common to all signs).
When determining the numerical value of the coefficients, it is necessary to take into account not only the degree of importance of this trait for the breed (this is indicated by the layout of the 100-point scale of the standard for articles), but also the value of the trait at the given moment of breeding work.
The breed characteristic rare for the cat population with which it is supposed to work will have a greater numerical expression than the one that is found in droves.
Of course, such an assessment of the breed traits will be in some sense subjective, but at least it will be necessary for the breeding workers to work with these animals.
Let us consider such an example. Let’s say you need to evaluate in comparison with Russian blue cats. The current population is currently represented by animals with a good shape of the head and the correct position of the ears, often the correct profile line and elegant addition are found. Unfortunately, the texture of wool, the shape and color of the eyes and the color tone of animals leaves much to be desired. First of all, the coefficients for each of these signs should be determined on a 10-point scale. The shape of the head and ear set at this stage of breeding can be considered as stabilized signs and not taken into account when making miscalculations – it is understood that these signs are equally well pronounced in all tested cats. Addition (C), that is, the body, limbs and tail, according to the breed standard can be estimated at 30 points from 100 total. This is a high figure, but in our population these signs are fairly well represented, so the coefficient will be below 10 points – say, 6. The profile line (LP), according to the standard, is included in the total head estimate for animals, numbering up to 25 points, besides this sign not rare in the tribal group. The coefficient for it can be estimated at 5 points. The double texture of wool (TSH) is a sign that is very “weighty” by the standard (20 points) and rare in our animals, so it will turn out to be the most selectively valuable: its coefficient will be equal to 10 points. The color and shape of the eyes (TG and FG) —with total points, distinguished by the standard for these signs, and their rarity in our group of Russian blue — on. each will have at least 8 points.
The coefficient for the tone color (TO) will be approximately 7 points.
Mandatory parameter, the assessment of which is added to the selective characteristics, with an indispensable factor of 10 points – is the health of the animal. This indicator includes not only morphological normality and absence of diseases, but also the cat’s sexual activity or the regularity of the cat’s estrous cycles. If the animals had cases of the birth of dead, abnormal or “sick kittens, the producer’s health index decreases.
As a result, to evaluate the Russian blue cats that interest us, we get the following formula:
10хЗД + 10хТШ + 8хЦГ + 8хФГ + 7хТО + 6хЬ + 5хЛ P.
Now we estimate the performance of each particular cat according to these characteristics, using 10-b. scale (table. 7).
The total index of the breeding index for each cat is made up of the sum of the indicators for each attribute multiplied by the corresponding coefficient. From the above testing of four cats, it is clear that the most promising as producers at the moment are individuals N2 and N4. Good results can be expected from the cat N1.
However, in addition to this method, it is possible to introduce a condition prohibiting the use in breeding of individuals, whose score on any of the selection indices is lower than 5 points. In this case, for breeding work, cats N1 and N2 remain.
Of course, in full this method is rarely used in practice, except that in the breeding group it is necessary to evaluate several cats with the same show scores.
All of the above selection methods are based solely on the assessment of the external qualities of the manufacturer.
However, everybody knows cases when champion cats, high title holders, gave birth to offspring that didn’t shine with exterior qualities. Therefore, it is not enough to base selection solely on the indicators of the producers themselves.
Additional information when choosing animals for breeding can be given their pedigree. Of course, for a full assessment of the pedigree you need to know the ancestors of the animal of interest to you, their advantages and disadvantages. However, some data can be obtained in addition to this. First of all, it is possible to approximately estimate the quality level of ancestors. Although the pedigree dazzling with champions does not guarantee the breeding value of a cat, it can still give information about its potential.
In addition, the pedigree can determine the degree of inbredness of the animal. Determining the degree of inbreeding is simple: it is enough to find duplicate nicknames in the ranks of the ancestors and figure out in which knee these nicknames are found.
Inbreeding is any kindred cross. Depending on how close the ancestors of the animal are related, it is possible to determine the degree, or rigidity, of inbreeding. According to the pedigree, this indicator is calculated, taking into account those of its ranks (generations) where the common ancestor is found. Inbreeding is recorded in Roman numerals, starting from the maternal side of the pedigree (Fig. 11).
There are four degrees of inbreeding stiffness:
• Close, or incest: I-II, II-I, II-II; .
• Close: I-III, III-I, II-III, III-II;
• Moderate: III-III, III-IV, IV-III, IV-IV;
• Remote: IV-V, V-IV, V-V.
These are cases of so-called simple inbreeding. However, complex inbreeding is quite common, i.e. more than one manufacturer.
To calculate the degree of such inbreeding, various versions of formulas are used, for example:
With this calculation, with a ratio of> 25%, inbreeding is considered close, 12.5–25% close, 1.5–12.5% moderate, 0.2–1.5% distant.
It is more difficult to determine the feasibility of inbreeding. In principle, the higher the degree of inbreeding in an animal’s pedigree, the better its signs are stabilized.
It is good if the breeder knows the qualities of those ancestors of the cat on whom the inbreeding was carried out. But, of course, in any case, it is better that the pedigree of, say, an experimental silver British inbreeding be carried out on a British cat, and not on a Persian cat of an unrecognized standard color.
The most realistic and most informative method of selection is the selection of producers by progeny. In this assessment, the most important importance is attached to the stability of the transfer by the manufacturer of characteristic breed traits when crossed with various individuals, or so-called prepotency.
Preventiveness is the ability of a producer to firmly transmit characteristic features or, more precisely, complexes of signs to offspring.
To give a complete theoretical justification for this phenomenon is not yet possible. It would seem that during the shuffling of genetic material in the generations, polygenically determined or recessive traits can in no way be stably transferred to descendants or have preferential inheritance. It is assumed that the phenomenon of prepotency is determined, on the one hand, by the occurrence of stable homozygosity on quantitative, polygeneously determined characteristics. On the other hand, an important role can be played by the complexes of regulatory elements established during the breeding work, which stabilize the activity of certain groups of genes.
In the simplest case, the formula can be used to calculate the manufacturer’s prepotency on some basis:
P = number of descendants with the desired trait / total number of descendants.
If not less than 10 different cats are used in matings with one cat, you can calculate the indicator of its prepotency differently:
P = number of descendants exceeding the indicators of this trait in mothers / total number of descendants.
Naturally, the higher the indicator of prepotency on the necessary characteristics of a cat, the better it is as a breeding producer. It is possible to evaluate prepotency not only by the need for the breed, but also by unfavorable features.
High prepotency in the first is as desirable as low in the second.
As a rule, such an assessment is carried out for manufacturers. Not because of gender discrimination, but only because a manufacturing cat is able to leave a much larger number of descendants than a breeding cat, at the same time. Therefore, the requirements for cats are higher than for females-producers.
The degree of selection stiffness and the number of animals in the breeding group are very closely related. This is especially true of new breeds. Working with an established breed, you can count on the acquisition of producers in other nurseries, domestic or foreign. In the case of breeding with a new breed with a hard selection, you can simply be left without producers. Therefore, when breeding such “young” breeds, it is worthwhile to begin target selection only when the number of animals reaches several even not tens, but hundreds of individuals. In addition, for several years of breeding with minimal selection, it is possible to determine the breeding capabilities of animals, the recessive carriage of harmful genes, the level of prepotency of individual individuals. So did, for example, in the United States in the development of Singapore. Americans started the intensive selection only when the number of descendants of the first five brought individuals reached six hundred. But this selection was really intensive: out of 600 cats only a third was allowed for further breeding.