Breeding and conservation of the gene pool in modern domestic poultry farming

To prevent a decrease in the vitality of the offspring, involve for mating birds of the same breed from other farms that differ slightly in genotype. Be sure to cull diseased individuals: a veterinary examination is conducted strictly at the same time as the zootechnical assessment.

The duration of a bird's use in breeding work is limited by its age. The majority of the chicken, duck, and turkey flock on breeding farms is renewed annually, leaving only the most valuable individuals. Although breeding qualities can be assessed at an early age, the best offspring are obtained from mature birds.

• Optimal age of birds for obtaining offspring — 1 year
• Usage period for breeding chickens, ducks, and turkeys — 2–3 years
• Usage period for breeding geese — 4–5 years

Evaluation and selection of poultry by conformation

Evaluation of poultry by external traits is based on the connection between conformation and internal productivity. In practical poultry farming, when grading (bonitierung) chickens between the ages of 7 and 30 months, all conformation traits are divided into three main groups. Such classification helps to predict flock productivity more accurately.

• Rapidly changing traits. These are closely related to the activity of the sex glands and change quickly depending on the season and age. They help to assess current egg production at the time of grading.
• Slowly changing traits. Subject to gradual age-related changes. They allow for an assessment of the intensity and duration of egg production up to the time of evaluation.
• Stable traits. Characterize the size, shape, and color of body parts. They reflect the bird's constitution, its health, and breed or line peculiarities.

A comprehensive analysis of these groups of traits allows for the prompt identification of the most productive layers. Based on the evaluation, the flock is divided into qualitatively different groups for further breeding. This contributes to the accelerated increase in the overall productivity of the poultry farm.

Evaluation of layers by body build and skin pigmentation

To quickly assess a layer's potential in a flock, it is sufficient to examine its body build and check the skin pigmentation. These signs allow for the accurate separation of highly productive birds from "duds" without the use of complex equipment. Special attention is paid to the proportions of the head, the capacity of the abdomen, and the condition of the pubic bones.

External markers of productivity vary depending on the bird's condition. The table shows key anatomical landmarks for culling layers. The evaluation is carried out by palpation and visual inspection.

Evaluation parameter	Highly productive layer	Low-productive bird	Coarse-built bird (cull)
Shape of head and beak	Broad, deep, moderately long; beak short, slightly curved.	Narrow, long ("crow-like"); beak long and thin.	Excessively broad and deep, often of "rooster" type.
Eyes	Bulging, shiny.	Dull.	Deep-set, sullen look.
Abdomen and body capacity	Soft, large. Distance from keel to pubic bones — 7–9 cm (the palm fits in a bird weighing about 2 kg).	Hard, small. Distance from keel to pubic bones — 4–6 cm (only 2–3 fingers fit).	Firm, fat-covered.
Pubic bones	Resilient, spread by 4–5 cm (3–4 fingers fit).	Rigid, ends brought together and slightly curved inward.	Rigid, thick, brought together.
Comb and wattles	Large, delicate, soft (during peak laying period).	Wrinkled, pale.	Wrinkled, pale, of coarse texture.
Skin and skeleton	Skin soft, elastic; skeleton strong, muscles well-developed.	Skin too thin, inelastic; skeleton thin, muscles weak.	Skin thick, coarse; skeleton massive, legs thick.

To determine how long a poultry bird has been laying and whether it has taken breaks, a natural indicator is used — pigmentation intensity. In yellow-skinned breeds, carotenoids are consumed for egg yolk coloration, so the tissues gradually pale as egg-laying progresses. The bleaching occurs in strict stages.

1. Ring of skin around the cloaca
2. Skin around the eyes
3. Earlobes
4. Beak
5. Front of the shank
6. Toes
7. Back of the shank

Molting Control and Principles of Selection

The timing and speed of feather replacement are directly related to egg productivity. Good layers enter the molt late and shed feathers quickly, with almost no interruption in egg-laying. Weak birds begin to molt as early as the beginning of summer, and this process stretches over several months.

• Target egg production of a hybrid — 280 or more large eggs per year
• Replacement of two primary flight feathers — 20% of molting progress
• Replacement of nine primary flight feathers — 90% of molting progress

The course of natural molting is monitored by the shedding of primary flight feathers, starting from the inner edge of the wing toward the outer edge. In cage poultry housing, this process is not linked to the season; however, intensive feather replacement always reduces overall egg collection rates. To return the flock to a working mode quickly, forced molting is used by adjusting the light period and diet.

At poultry farms with floor housing, primary culling is carried out when assembling the flock, regularly removing unproductive and broody individuals throughout the year. In small farming operations, strict selection is traditionally planned for autumn to replace older birds with younger ones. When evaluating geese, ducks, and turkeys, similar markers are used, but meat quality traits — such as back width and pectoral muscle development — are additionally considered.

Selection of birds by exterior and individual productive qualities is undoubtedly of great importance in the early stages of breeding work, but as the flock reaches high productivity, the potential embedded in these methods gradually decreases.

Selection and matching of birds based on breeding qualities. Breeding selection and matching allow for the most reliable reproduction of the parents' high productive qualities in offspring and serve as the basis for breeding poultry in lines. The direction, methods of matching, and the traits used to guide it are linked to this. Matching does not exclude selection but interacts closely with it.

Breeding matching when conducting line breeding is carried out taking into account the origin, productivity of parents and more distant ancestors, mainly P and PP generations, the productivity of offspring, as well as the sisters of young males. When matching birds, the goal is always for them to be more productive compared to the entire population or the selected flock. When selecting for heterosis and producing hybrid poultry, through the use of periodic reciprocal selection or other methods, heterogeneous matching of different lines of the same, or more often different, breeds of the same productivity direction is used. Unlike line breeding, the results of matching in hybridization are evaluated by the quality of the hybrid offspring, not purebred ones. In both cases, similar traits are compared, contrasting them with the traits of the birds used in the selection.

Artificial insemination makes it possible to increase the number of females assigned to a male several times over. When line breeding, each line includes a number of pens where matching is differentiated by specific traits within the general direction of the line's selection.

To ensure a reliable evaluation of a rooster, it is necessary to obtain about 100 daughters and dozens of the best-developed sons from him, and from each hen at least seven daughters, which are then tested for the selected traits. As early as 8—9 weeks later, one can draw conclusions about the results of improving meat qualities. As for egg production, accelerated evaluation allows one to judge the success of the work after 10 months, while a full evaluation of egg productivity and other weakly inherited traits requires about 11/2 years, counting from the time of hatching. To verify the breeding qualities of the sires, hens with similar productivity are matched in the pens.

However, it remains unclear whether the sire being tested is an improver for poultry with a different, higher or lower productivity than the hens assigned to him. This requires a new selection of poultry and repetition of the work. The Department of Poultry Science of the TSHA has proposed a method for accelerated evaluation of roosters. To do this, hens with different levels of annual egg production are selected for the nests. Each rooster was mated with hens from two groups, whose productivity was 250 and 190 eggs per year, and 84 and 65 for the first four months of laying, respectively.

It was revealed that some roosters (No. 1, 2, 3, 4) were improvers for hens of all groups. Egg production of the offspring from the medium-productivity group exceeded the productivity of the mother hens by 21—

Table 16. Quality of daughters of the roosters being tested by average productivity for 4 months. Egg production of daughters. Superiority of daughters over mothers (%). Number of roosters tested. Highly productive hens. Medium productive hens. Highly productive daughters. Medium productive daughters. Highly productive hens. Medium productive hens. 1 84.4 65 90.0 + 1.69 | 80.0 + 2.5 | +8 + 23 2 83.0 65 88.6 + 2.31 | 83.0 + 4.5 - 6.7 = 21.3 3 84.0 65 87.0 + 2.8 | 78.9 + 3.7 - 4.8 + 21.0 4 84.4 65 86.5 + 1.58 | 81.0 + 2.25 | +2.5 + 24.5 5 84.4 65 82.0 + 3.1 | 74.0 + 4.4 - 2.4 - 14 6 88.4 65 84.4 + 2.7 | 80.7 + 3.5 - 4.1 + 23.5 7 84.0 65 71.4 + 2.28 | 73.0 + 2.6 - 8.0 - 12.5

27%, and hens of the high-productivity group — by 2.5—3%. Some roosters (No. 5, 6, 7) also proved to be improvers for hens with medium productivity. Their offspring exceeded the egg production of their mothers by 12—23%. However, the offspring of these roosters from high-productivity hens subsequently yielded less (by 2.4—8%) than their mothers in egg production. Thus, it turned out to be possible, within one mating period, to differentiate sires by the transmission of such a heritable trait as egg productivity to the offspring.

To test a large number of poultry during the breeding season, mating hens with replacement roosters is used. A rooster is kept with a group of hens for only about two weeks and then replaced by another in accordance with the breeding plan. On the day a new rooster is introduced, the hens are artificially inseminated with its sperm. This allows eggs to be obtained after just a few days, from which chicks originating from the new rooster are hatched.

When developing and improving egg lines, selection is carried out based on sexual maturity of young hens, egg production for 68 weeks of life and for the year of laying, egg fertility, hatchability of quality chicks, viability of young and adult birds, etc.

Accelerated evaluation of breeding qualities of sires can be carried out by comparing the productive qualities of the offspring with the qualities of the parents for the same period of life or at a similar age (Table 17).

Table 17. Evaluation of breeding qualities of dual-purpose hens by productivity of sisters and daughters for 10 months of life

Egg production. Evaluated hens. Sisters. Daughters. 31—40 38 40 43 41—50 48 42 44 51—60 55 54 55

Additional evaluation methods include comparing the productive qualities of the offspring with the qualities of the entire family and line, the coefficient of variation of selection traits, and other indicators. Accelerated evaluation is important for the selection of the most valuable young roosters based on the productivity of sisters, compared with the productive qualities of the mothers of the sire roosters. Poultry evaluated for breeding qualities is used for factory mating as early as one year of age, which significantly accelerates selection.

Table 13. Evaluation of breeding qualities of young roosters by the productivity of their sisters for the first 10 months of life

Group. Egg production of mothers. Egg production of sisters. Average mass. I 232 56 57 II 198—221 48—49 56 III 202—203 39—42 55—54

Studies by V. A. Sergeev have established that although absolute egg production indicators differ in hens hatched in spring, autumn, and winter, the accelerated evaluation based on these indicators is reliable regardless of the hatching season.

Table 19. Accelerated evaluation of breeding qualities of poultry hatched in different seasons of the year. Egg production for the first months of laying (pcs.). Average mass of eggs obtained from hens at the age of 12 months (g).

39 94 92 95 60 59 60 77 95 94 96 60 59 60 89 99 96 101 59 59 60

This makes it possible to carry out factory mating at least three times throughout the year, and essentially to develop and implement three mating plans per year. At the same time, accelerated evaluation makes it possible to identify the best poultry and reduce the expenditure of funds and labor on recording poultry productivity throughout the year. Only poultry that received a good rating after the accelerated test are kept for recording.

When developing egg lines and maternal forms in meat poultry farming, selection and matching aimed at increasing egg productivity are carried out based on the number of eggs per 68 weeks of life and for the year of laying, and the accelerated evaluation of hens of egg lines is carried out at 39 weeks, and for meat lines — at 34 weeks. The intensity of egg production, which is expressed as a percentage for a selected period of time, for example, for one or several months and for the year, is also taken into account. Selection based on sexual maturity is related to the evaluation of hens by their age at the time of laying the first egg. A selection trait can also be the cyclicity of egg production, evaluated by the length of the cycles — the number of eggs laid without interruption during the first two months of productivity. Selection and evaluation of egg productivity in ducks, geese, and turkeys are carried out for the cycle of the first year of laying, and the accelerated evaluation — for its first three months.

Breeding for improved egg quality is primarily linked to increasing egg mass. Selection is carried out in accordance with standard requirements for the weight of each egg laid in the last ten days of the 8th and 12th month of the hens' life. To obtain uniform egg products, evaluating the egg by measuring along its major and minor axes is important for selection. The quality of the protein and yolk is determined by candling; devices are being developed to obtain objective indicators of these egg qualities. During candling, the presence of meat and blood inclusions is also established. Hens that produce eggs with such inclusions are culled.

Breeding for increased shell strength is of great importance. The thickness and the associated shell strength can be determined by the specific gravity of the egg by immersing it in a solution of sodium chloride. A solution specific gravity of 1.070, at which the egg is in a suspended state, corresponds to a shell thickness of 0.29 mm, and with better shell quality, 1.080—0.33, 1.090—0.97, and 1.095—1.4 respectively. At the Leningrad Agricultural Institute, a method was developed and an instrument—an elastic meter—was constructed to measure in microns the increase in the minor diameter of the egg after removing a 500 g load from it. This allows for a fairly quick and accurate indirect determination of shell thickness without any damage to the egg. The correlation coefficient between the elastic deformation of eggs and shell thickness ranges from —0.750 to 0.892 (P-0.01). A fairly high correlation between egg elastic deformation and hatchability has been identified: 0.363 -+ 0.030.

Table 20. Elastic deformation of eggs and hatchability (according to P. P. Tsarenko)

. Hatchability (%) Elastic deformation Laid Hatched (microns) eggs of the number of of the number of set eggs | fertilized eggs 20—34 297 258 86.9 | 94.2 35—49 1331 1118 84.0 Uzi 50 or more 291 227 78.0 | 81.3

At the All-Union Research Institute of Animal Breeding and Genetics livestock animal it has been proposed to evaluate roosters based on sexual activity. The sexual behavior of hens and roosters is evaluated by the frequency of matings during the day, which, apparently, is genetically determined. Offspring from active hens and roosters are distinguished by higher egg productivity and egg fertility than offspring from passive poultry. At the same time, it must be borne in mind that an excessive number of matings leads to a deterioration in the condition of the roosters' organism and a decrease in egg fertility and hatchability. The rations of breeding roosters must be biologically complete.

Evaluation and selection of poultry for meat qualities are carried out by weighing young birds at an age close to slaughter: meat chickens at 7 weeks of age, turkey poults at 13—14, goslings at 9, and ducklings at 7 weeks of age. Replacement chickens are weighed at 20 and 34 weeks of age. Based on the speed of feathering, meat chickens of the paternal form are selected at 7—8 weeks of age, and the maternal form at 8 weeks of age. When selecting adult poultry, mass is recorded at one year of age.

When selecting poultry for meat qualities, development of thigh and breast muscles, carcass grading in accordance with the standard, and the ratio of edible to inedible carcass parts are taken into account.

The main indicators of reproductive qualities are egg fertility and hatchability, survival of young birds and adult poultry, taking into account mortality and forced culling, and the yield of young birds from each breeding bird.

To assemble breeding pens and ensure high egg fertility, roosters are selected based on the quality of sperm production. The evaluation is carried out based on three key indicators: ejaculate volume, motility, and sperm concentration. Based on these data, males are divided into classes, with the best individuals admitted to breeding work.

• Ejaculate volume for Class 1 — 0.5—0.3 ml
• Sperm motility for Class 1 — 100—90 points
• Sperm concentration for Class 1 — 7—4 million

When selecting pairs for herd reproduction, the breeder always strives to exceed current productivity indicators. As soon as the planned level is reached, new tasks are set for the farm to create even more highly productive lines. This principle is universal: breeding work in turkey, duck, and goose farming is built on the same rules as in work with meat lines of chickens.

Annual Class Appraisal of the Herd

An annual appraisal helps to determine the breeding value of poultry and distribute it into classes. This is a mandatory procedure for breeding farms, which is carried out strictly according to regulations. Before starting an individual examination, specialists perform a detailed analysis of the array of accumulated breeding records.

1. Collection and processing of breeding records for a preliminary assessment of poultry productivity and breeding qualities.
2. Verification of the qualities of the evaluated poultry based on the offspring obtained from it.
3. Individual assessment of poultry by conformation, productivity, and breeding value, followed by class assignment.