Development of extraembryonic organs and the economics of industrial egg incubation

Amnion and allantois development during the incubation period

Monitoring the development of extraembryonic organs allows for the timely detection of disturbances in the egg incubation regime. At the beginning of development, the amnion tightly envelops the embryo and is subsequently filled with fluid containing dissolved mineral salts. This creates optimal osmotic pressure and protects the embryo from mechanical damage. During the second half of incubation, the amnion serves as a nutritional organ for the embryo, through which it absorbs egg white.

The allantois originates on the 3rd day of incubation as an outgrowth from the posterior part of the primitive gut. By the 5th day, it expands over the embryo and amnion; on the 6th day, it reaches the inner shell membrane, and by the 10th day, it covers the embryo, yolk, and white along the entire inner surface of the shell. Connected to the embryo's body by the allantoic stalk, this organ takes on the respiratory function from the 5th–6th day. Blood in its vessels is supplied with oxygen from the surrounding air through the shell pores and releases carbon dioxide. Respiration via the allantois continues until the end of the 19th — beginning of the 20th day.

The growth of the allantois directly influences the absorption of nutrients. Through the pressure of its walls, it forces the white to move through the sero-amniotic canal into the amnion. Also, with the help of the allantois, the embryo absorbs calcium from the shell. Combining with carbon dioxide, calcium changes from oxide to soluble calcium bicarbonate and enters the allantoic vessels. On the 19th–20th day of incubation, this organ atrophies, its vessels become bloodless, the fluid evaporates, and the chick transitions to pulmonary respiration.

• Appearance of the allantois — 3rd day of incubation
• Beginning of respiration through the allantois — 5th–6th day
• Full coverage of the shell by the allantois — 10th day
• Atrophy of the allantois — 19th–20th day
• Incubator turnovers for year-round operation — 10–12
• Incubator turnovers for seasonal operation — 4–5

Economic efficiency of year-round incubation

Modern poultry farming is focused on year-round incubation, hatching, and rearing of young stock in all seasons. The experience of large specialized farms shows that birds can be hatched in large batches, placing 20–30 thousand heads simultaneously. This allows for the annual rearing of 4–5 million young birds. At the same time, in non-specialized farms, chicks, ducklings, and goslings are raised mainly in the spring and summer months, when natural temperature, daylight hours, and local feed facilitate this process.

Year-round incubation provides poultry farms with undeniable advantages over seasonal hatching. It ensures continuity of rearing of young stock and rhythmic replenishment of the laying flock. As a result, egg and meat production proceeds evenly throughout all months of the year. With such organization, all departments of the farm work at full capacity — from the parent flock to product processing.

With year-round egg setting, incubators are used much more efficiently. Each unit performs 10–12 turnovers per year instead of 4–5 turnovers during seasonal operation. Increasing hatching volumes reduces the cost of each hatched chick or duckling. This occurs due to a decrease in the share of depreciation and overhead costs per unit of production.

Hatchery organization and premises requirements

Large-scale poultry production requires regular setting of eggs in incubators — daily or every 2–3 days. To obtain a stable volume of quality eggs year-round, the parent flock is formed from birds of different ages and different hatching seasons. Such a flock structure stabilizes the average monthly egg production, gross output, and fertility and hatchability rates.

The hatchery building is constructed of brick or cinder blocks on a dry plot with a slight slope for water drainage. Floors are made perfectly level, without thresholds, using cement or ceramic tiles. The premises are divided into technological zones: from the egg storage and incubation halls to washing areas and laboratories.

• Temperature in the incubation hall — 18–22 °C
• Air humidity in the hall — about 60%
• Height of wall tiling — 1.8 m

Criteria for selection and grading of hatching eggs

Grading by weight is critically important, as egg size directly influences the embryo's development rate. Young stock from small eggs hatch faster, and from large ones — later. Setting uniform-sized batches ensures simultaneous hatching and equal live weight of day-old chicks.

1. Delivery of eggs to the hatchery egg storage.
2. Calibration on a specialized machine by weight categories.
3. Loading of calibrated eggs into trays.
4. Culling of defective eggs based on external appearance and candling results.

When raising waterfowl and turkeys for meat, almost all eggs obtained are sent for incubation, culling only obvious defects. During candling, the position of the air cell is monitored: it should be located strictly at the blunt end of the egg. If the cell, with a diameter of 10–15 mm and a height of 1.6–2 mm, is shifted to the side or towards the sharp end, the embryo will find it difficult to breathe and break the shell during hatching.

A high-quality yolk should be in the center of the egg and slowly return to its place when rotated. A bright yellow or orange yolk color indicates proper feeding of the hen with vitamins. Robust, viable young birds hatch from such eggs.

Special attention is paid to the density of the albumen. Thin albumen does not hold the yolk in the center, causing it to float quickly and stick to the shell. Eggs with thinned albumen are unsuitable for incubation and must be culled.

Eggs unsuitable for incubation include those of irregular shape (round, long, compressed), those with shell defects (cracks, hairlines, thin shell, calcium deposits), those with a shifted, mobile, or wandering air cell, those with blood or meat spots, old eggs, broody-hen eggs, dirty eggs, double-yolk eggs, and those with ruptured chalazae.

Egg storage. The storage period for eggs before incubation should not exceed 3–5 days. The sooner eggs are placed in the incubator after laying, the higher the hatch rate and the better the quality of the resulting young birds will be. Every extra day of storage reduces EGG HATCHABILITY.

When storing eggs in the egg storage room, the temperature is maintained between 8–12 °C, and the humidity between 70–80%. The egg storage must be well-ventilated. The air should not be dry to prevent excessive water evaporation from the eggs, while excessive humidity causes dampness and mold growth. In large hatcheries, the egg storage rooms are equipped with special devices to maintain the set temperature and humidity. Chicken, turkey, guinea fowl, and small duck eggs are stored vertically with the blunt end up. Large duck eggs are stored in a semi-inclined position, and goose eggs in a horizontal position. If eggs are stored for more than five days, and especially in a horizontal position, they should be turned once a day by 90°.

Eggs selected for incubation are stored on incubation trays. When storing eggs from pedigree hens, where it is important to collect eggs from the same hen together, special racks with sliding trays are used in the egg storage, which have holes for placing the eggs. In some cases, production requires storing eggs for longer periods; for example, growing broilers requires large batches of day-old chicks. Breeding eggs must also be stored for a long time when it is important to obtain a large number of same-age young birds from a hen. Currently, methods have been developed for long-term storage of incubation eggs that delay the aging process of the eggs.

Incubator characteristics. An incubator is a device for hatching birds. Conditions necessary for the development of embryos in eggs and for hatching are created and maintained within it. An incubator consists of one or more chambers (or boxes) equipped with a set of trays for holding eggs and equipment for installing them inside the chamber or box. Eggs are placed vertically or horizontally on incubation trays, but only horizontally on hatching trays. The trays are made durable yet lightweight so that the operator can lift a tray filled with eggs. The trays are installed in the incubator chamber in several tiers in a drum, in hanging columns, or on block-trolleys. During the incubation process, the eggs must be turned systematically. Turning is performed automatically.

During incubation, eggs absorb oxygen and release carbon dioxide. A constant supply of fresh air is essential for them. Air inside the incubator must be continuously circulated so that its temperature and humidity are uniform throughout the volume of the chamber or box. The air entering the incubator is heated, humidified, and circulated. Ventilation operates constantly; otherwise, the required conditions cannot be maintained in all zones of the incubator.

All modern incubators operate on electric heating. Heaters are switched into the power circuit automatically based on signals from the temperature controller, the most critical part of which is the sensor that reacts to changes in air temperature. Thanks to thermostats, the temperature in the incubator is maintained at a set level, with heating switched on as needed. The air in the incubator must have a specific relative humidity. Humidifiers are installed to humidify it. Devices that spray moisture into the airflow are used. Relative humidity of the air">Relative humidity of the air is regulated by automatic instruments and maintained at a set level.

During the second half of incubation, eggs release a significant amount of heat. Therefore, they sometimes require cooling. There are air-based and air-water cooling systems. With air cooling, excess heat is removed through air exchange with the space outside the incubator, where the air temperature is lower. The cooling system is switched on automatically and is controlled by a thermostat.

The incubator housing has good thermal insulation; on its front side, there is a door for inserting trays or moving in carts with eggs. The incubator is supplied with power from a three-phase AC network with a voltage of 380/220 V or 220/127 V. A necessary condition for the operation of the incubator is a continuous power supply.

All equipment and electrical instruments are mounted on a control panel located outside the incubator. Signaling is visual and audible; it monitors the operation of fans, heaters, coolers, and humidifiers. Currently, factories produce domestic incubators that are fully electrified, mechanized, have automatic mode control, and are equipped with a signaling system. Such incubators include

| "Universal-15" | "Universal-45" | "Universal-50" | "Universal-55" | IKP-90 "Kavkaz" | Total capacity, chicken eggs | 15,600 | 43,680 | 50,781 | 56,000 | 91,728 | Hatcher capacity, chicken eggs | 3,120 | 6,240 | 6,430 | 8,000 | 13,104 | Number of incubation trays, pcs. | 104 | 312 | 312 | 312 | 624 | Number of hatching trays, pcs. | 26 | 52 | 52 | 52 | 104 | Tray capacity, chicken eggs | 120 | 120 | 142 | 156 | 126 | Turning frequency | every 3 h | every 30 min | | Supply voltage, V | 380/220 or 220/127 | 380/220 or 220/127 | 380/220 or 220/127 | 380/220 or 220/127 | 380/220 | Incubator dimensions, mm: incubation | 2940x2385x2554 | 5220x2354x2554 | 5340x2435x2200 | 5155x2700x2216 | 14720x2810x2595 | hatching | 2940x2385x2554 | 1828x2240x2554 | 2128x2455x2216 | 1704x2700x2215 | |

Fig. 49. IKP-90 "Kavkaz" incubator.

the "Universal", IKP-90 "Kavkaz", and box-type incubators. The characteristics of the incubators are presented in Table 27.

Loading eggs into incubators. Every hatchery draws up an egg-loading schedule in advance. Loading eggs according to a schedule with the trays placed on precisely established tiers of drums or columns ensures the proper operation of the incubator. Violating the loading schedule reduces the incubator's capacity, as well as the hatch rate and the quality of the young stock. Furthermore, the incubation regime is disrupted.

The goal is always to load trays of eggs into the incubator at the same hours. Several hours before loading, the trays are transferred from the egg storage to the hatchery. This is done so that the eggs can warm up slightly (the temperature in the egg storage is 8—12 °C, while in the hatchery room it is 18—20 °C). If the eggs are not warmed up but loaded directly from the storage into the incubator, a sharp disruption of the incubation regime will occur. When loading 8—10 thousand eggs, the air temperature in the incubator will drop sharply. Loading cold eggs leads to the condensation of water vapor on the shell surface. Additionally, it will take significantly longer to restore the temperature and humidity to the standard levels.

The distribution of temperature in the incubator and the heating of the eggs depend on how correctly the trays with eggs from different batches are placed. Embryos not only experience the influence of the incubation regime but also influence it themselves (during the first half of incubation, eggs absorb heat; during the second, they release it). The heat radiation from eggs with older embryos provides additional heating to the eggs located nearby. When placing trays into the drums or cross-beams of the incubator, trays with newly loaded eggs should be placed between previously loaded batches. In this case, eggs with younger embryos absorb heat, while eggs with embryos at later stages of development release it.

When loading eggs into incubators, it is recommended to strictly follow the existing instructions. The loading patterns for the "Universal" incubator can vary and depend on the number of eggs to be incubated. For example, chicken eggs are loaded into the "Universal-45" incubator as follows: six batches every three days, and the next batch after four days, then the cycle repeats again. Or, suppose a farm needs to hatch 10,000 chicks every other day. In this case, it is necessary to have three "Universal-45" incubators and to load eggs every other day as well. Simultaneously, eggs are loaded into two cabinets with 6,240 eggs in each, for a total of 12,480 eggs.

If, for example, a broiler poultry farm needs to receive 10–12 thousand chicks daily, the hatchery must have seven "Universal-50" incubators. Eggs are loaded daily, and each batch consists of 14 thousand eggs. Every day, eggs are loaded into two cabinets with 6240 eggs each, and the remaining 1520 eggs are placed in the cabinets of the seventh incubator.

When loading eggs into the IKP-90 "Kavkaz" incubator, block-trolleys are loaded with egg trays, then rolled into the chamber, the doors are closed, disinfection is carried out, after which the chamber is ventilated, and then the automation is switched on to ensure the set regime.

` Incubation regime. The incubation regime is created by a specific combination of physical factors: temperature, relative humidity, and air exchange. To increase the hatchability of young birds, techniques such as egg turning, cooling, and others are also used.

For the proper development of embryos, specific conditions are necessary, changing in accordance with their age. If the incubation regime corresponds to the good and timely assimilation of egg nutrients and ensures embryonic respiration, it means it is set correctly. But the change in food sources and the mechanism of respiration and nutrition of the embryos makes it necessary to change the regime in accordance with the period of their development. Considering the changes that occur in the nutrition and respiration of embryos, as well as in their growth and development, it is recommended to warm up the eggs well in the first days of incubation and maximize water retention in them. This is achieved by maintaining a higher temperature and increased humidity.

During the middle days of incubation, heating is reduced, air exchange is increased, and humidity is lowered. It should be noted that when incubating eggs of waterfowl, it is necessary to monitor the decrease in humidity with particular care during the middle period of incubation. As hatching approaches, the internal egg temperature rises significantly. Therefore, egg heating is reduced, but air exchange and humidity are significantly increased. N. P. Tretyakov and his colleagues developed and recommend an incubation regime with egg cooling. Periodic short-term cooling of eggs has a beneficial effect on developing embryos. In this case, embryonic mortality decreases, and the hatchability of young birds increases by 2–4% above the standard.

Temperature. In modern incubators, eggs receive heat from heated air; the heating is uniform at all points of the egg. Experiments have established that a developing embryo tolerates a temporary drop in temperature well but is very sensitive to an increase in it.

In different periods of incubation, the same temperature level has an unequal effect on the growth and development of the embryo. In the first days of incubation, embryonic development can proceed normally at a temperature slightly higher than standard, which would cause death during other periods of incubation. During the first days, the embryo reacts to a temperature increase by accelerating development and growth. In the following days, the growth rate under the influence of temperature increase slows down, and in the last days of incubation, high temperature is unacceptable.

A low temperature at any period of incubation retards the growth and development of embryos. With prolonged exposure to low temperature, embryos usually lag in development and cannot always compensate for this delay. Due to underheating, deep metabolic disorders occur in them, leading to pathological phenomena and death.

Air humidity in the incubator directly regulates the heat dissipation of the egg and affects the water exchange of the embryo. It is through this mechanism that proper metabolism is triggered in the organism of the future chick. At the same time, the need for a specific level of humidity changes at different stages of embryo development, so the regime must be adjusted throughout the entire incubation period.

Air exchange and ventilation parameters

The developing embryo breathes continuously, absorbing oxygen and releasing carbon dioxide. Good ventilation improves the qualitative and quantitative indicators of bird hatching. The need for clean air arises even before loading the eggs into the incubator and persists in the earliest stages of embryonic development.

In modern incubators, a very large batch of eggs accounts for a unit of space. In such conditions, the rate of air renewal plays a decisive role. Furthermore, the movement of air in the chamber is necessary for uniform heating of the entire load.

• Minimum oxygen content in the air — 15 %
• Dangerous concentration of carbon dioxide — 1 %
• Egg placement density in the chamber — 1.5–2 thousand pcs/m³
• Air movement speed — 2 m/s or more