Stages of development of a chick in an egg. Embryo development in an egg How a chick develops in an egg

Everyone knows that eggs consist of white and yolk, that a chicken develops from the yolk, and the shell protects it from the outside world. . . However, everything is not so simple. The development of a chick in an egg takes place in several stages, each of which has unique features and requires special conditions for the successful birth of a chick.

Zoologists have long recognized the importance of studying the development of a chick embryo in an egg. Famous scientists, both Russian and foreign, have studied this issue. The result of their work was the emergence of several classifications of chicken development, based on different basic principles.

Studies have shown that violation of environmental conditions (outside the egg shell) - temperature, humidity, and sometimes light - leads to disturbances in the development of chickens and a decrease in the number of healthy livestock. Moreover, violations of the conditions for keeping eggs during certain periods entail clearly defined violations in the bird, which makes it possible to control the situation.

Russian science has long been developing on the principles of T.D. Lysenko, which states that stages of development are distinguished in accordance with changes in the requirements of the embryo itself to the external environment. On this basis, the following were distinguished. The first one is 12-16 hours. At this time, the eggs are resistant to periodic heating up to 41 degrees and cooling, the ability to develop the embryo can be extended up to 3 weeks. The second is 16-48 hours, when heating, on the contrary, contributes to the development of multiple deformities in the embryo. Third - 3-6 days. During this period, all the main organs and allantois (a sac in which toxins and waste products of the embryo accumulate, as well as the respiratory organ) are formed. In particular, on the 3rd day the head of the embryo separates, on the 4th day the rudiments of legs and wings are formed, the embryo turns on its side. By day 6, eyes, eyelids, fingers and toes are formed. At this time, constant high temperature and humidity are important for the development of the chick. Fourth - days 6-11. From the 7th day, the allantois takes over the respiratory function, on the 8th day the gonads begin to differentiate, and by the 10th day the feather papillae are formed. By the 11th day, the future scallop is formed, and the allantois occupies the entire area of the egg and is separated from the shell, which is an important indicator of development. The embryo becomes like a bird. It weighs 3.5 g and measures 25 mm. During this period, increased temperature and humidity will retard the development of the bird.

On the 20th day, the shell pecks. This leads to an increase in the level of oxygen inside the egg, with the release of carbon dioxide and ammonia into the surrounding air, the body of the chicken is greatly cooled. The chick inhales oxygen for the first time. By day 21, the chick has completely pecked outward.

Fifth stage: from day 12, the embryo switches to allantois respiration completely. High humidity and temperature have an extremely negative effect on the rate of development. The future chicken develops a crest and fluff. Sixth stage - 15-19 days. From day 15, protein reserves run out and the embryo switches to feeding on yolk substances. Nostrils and toenails are formed. The baby is already 60 mm tall. As the chick develops in the egg, thermoregulation of the embryo begins, the temperature of the egg increases, but environmental conditions cease to have a significant impact on development. By the 18th day, the fluid reserves in the allantois are completely exhausted, by the 19th, the blood vessels of the allantois degenerate, the yolk sac is retracted into the abdominal cavity of the chicken.

It is obvious that the process of forming a living bird from an egg is complex and multifaceted. However, scientists were able to systematize information about it and identify the main periods and conditions that have the greatest impact on the development of healthy, strong chickens and the reduction of embryonic mortality.

During the incubation period, the embryo changes its position several times at a certain time and in a certain sequence. If at any age the embryo takes an incorrect position, this will lead to a developmental disorder or even the death of the embryo.
According to Cuyo, initially the chicken embryo is located along the minor axis of the egg in the upper part of the yolk and faces it with its abdominal cavity, and its back towards the shell; on the second day of incubation, the embryo begins to separate from the yolk and simultaneously turn onto its left side. These processes begin from the head part. Separation from the yolk is associated with the formation of the amniotic membrane and the immersion of the embryo in the liquefied part of the yolk. This process continues until approximately day 5, and the embryo remains in this position until the 11th day of incubation. Until the 9th day, the embryo makes vigorous movements due to contractions of the amnion. But from this day on, it becomes less mobile, since it reaches a significant weight and size, and the liquefied part of the yolk is used by this time. After the 11th day, the embryo begins to change its position and gradually, by the 14th day of incubation, takes a position along the major axis of the egg, the head and neck of the embryo remain in place, and the body descends down to the sharp end, turning at the same time to the left .
As a result of these movements, the embryo lies along the major axis of the egg at the time of hatching. Its head is facing the blunt end of the egg and tucked under the right wing. The legs are bent and pressed to the body (between the thighs of the legs there is a yolk sac that is retracted into the body cavity of the embryo). In this position, the embryo can be released from the shell.
The embryo can make movements before hatching only in the direction of the air chamber. Therefore, he begins to protrude his neck into the air chamber, stretching the embryonic and shell membranes. At the same time, the embryo moves its neck and head, as if freeing it from under the wing. These movements lead first to the rupture of the membranes by the supraclavicular tubercle, and then to the destruction of the shell (pecking). Continuous movements of the neck and pushing away from the shell with the legs lead to rotational movement of the embryo. In this case, with its beak, the embryo breaks off small pieces of the shell until its efforts are sufficient to break the shell into two parts - a smaller one with a blunt end and a larger one with a sharp one. Releasing the head from under the wing is the last movement, and after this the chick is easily freed from the shell.
The embryo can take the correct position if the eggs are incubated in a horizontal as well as a vertical position, but always with the blunt end up.
When large eggs are placed vertically, the growth of the allantois is disrupted, since the inclination of the eggs by 45° is not sufficient to ensure its correct location at the sharp end of the egg, where by this time the white is pushed back. As a result, the edges of the allantois remain open or closed so that the white ends up at the sharp end of the egg, uncovered and not protected from external influences. In this case, the protein sac is not formed, the protein does not penetrate into the amnion cavity, as a result of which the embryo may starve and even die. The protein remains unused until the end of incubation and can mechanically impede the movements of the embryo during hatching. According to the observations of M. F. Soroka, from eggs of ducks with complete and timely closure of the allantois, a high hatching rate of ducklings was obtained with the shortest average duration of the incubation period. The protein in eggs with an untimely closed allantois remained unused even on the 26th day of incubation (in eggs with a timely closed allantois, the protein disappeared already by the 22nd day of incubation). The weight of the embryo in these eggs was approximately 10% less.
Good results can be obtained by incubating duck eggs in a vertical position. But a higher hatching percentage can be obtained if the eggs are moved to a horizontal position during the period of growth of the allantois under the shell and the formation of the albumen sac, that is, from the 7th to the 13th-16th day of incubation. In the case of a horizontal position of duck eggs (M. F. Soroka), the allantois is positioned more correctly, and this leads to an increase in hatching by 5.9-6.6%. However, this increases the number of eggs with the shell pecked at the sharp end. Moving duck eggs from a horizontal position after the closure of the allantois to a vertical position led to a decrease in pecking at the sharp end of the eggs and to an increase in the percentage of ducklings hatching.
According to Yaknyunas, at the Brovary hatchery and poultry station, the hatchability of ducklings reached 82% in the case when the trays were not replenished with eggs after removing waste during the first viewing. This made it possible to incubate duck eggs from the 7th to the 16th day of incubation in a horizontal or highly inclined position, after which the eggs were again placed in a vertical position.
To ensure that the position of the embryo changes correctly and the shells are positioned correctly, periodic rotation of the eggs is used. Rotating the eggs has a beneficial effect on the nutrition of the embryo, on its respiration and thereby improves development conditions.
In a stationary egg, the amnion and embryo may adhere to the shell during the early stages of incubation before being covered by the allantoic membrane. At later stages, the allantois and the yolk sac may become fused, which precludes the possibility of the latter being safely retracted into the body cavity of the embryo.
The disruption of the closure of the allantois in chicken eggs under the influence of insufficient egg rotation was noted by M. P. Dernyatin and G. S. Kotlyarov.
When incubating chicken eggs in a vertical position, it is customary to turn them 45° in one direction and 45° in the other. Turning of eggs begins immediately after laying and continues until hatching begins.
In the experiments of Byerly and Olsen, they stopped turning chicken eggs on the 18th and 1-4th days of incubation and obtained the same hatching results.
In duck eggs, a small rotation angle (less than 45°) leads to impaired growth of the allantois. If the vertically positioned eggs are not tilted sufficiently, the white remains almost motionless and, due to the evaporation of water and an increase in surface tension, becomes so tightly pressed to the shell that the allantois cannot penetrate between them. When the eggs are positioned horizontally, this happens very rarely. Rotating large geese eggs only 45° is completely insufficient to create the necessary conditions for allantois growth.
According to Yu. N. Vladimirova, with an additional rotation of goose eggs by 180° (twice a day), normal growth of the embryo and the correct location of the allantois were observed. Under these conditions, hatchability increased by 16-20%. These results were confirmed by A. U. Bykhovets and M. F. Soroka. Subsequent experiments showed that it is necessary to additionally rotate geese eggs by 180° from the 7-8th to the 16-19th day of incubation (the period of intensive allantois growth). Further rotations of 180° are significant only for those eggs in which the closure of the edges of the allantois is for some reason delayed.
In sectional incubators, the air temperature at the top of the eggs is always higher than the temperature at the bottom of the eggs. Therefore, turning the eggs here is also important for more uniform heating.
At the beginning of incubation, there is a large difference in temperature - at the top of the egg and at the bottom of it. Therefore, frequent turns of eggs 180° can lead to the fact that the embryo will many times fall into the zone of an insufficiently heated part of the egg and this will worsen its development.
In the second half of incubation, the temperature difference between the top and bottom of the eggs decreases and frequent turning can promote heat transfer by moving the hotter upper part of the eggs to a lower temperature zone (G. S. Kotlyarov).
In sectional incubators with one-sided heating, turning the eggs instead of 2 to 4-6 times a day improved incubation results (G. S. Kotlyarov). With 8 egg turnings, embryo mortality decreased, mainly in the last days of incubation. The increase in the number of turnings led to an increase in the number of dead fetuses. When the eggs were turned 24 times, there were many dead embryos in the first days of incubation.
Funk and Forward compared the results of incubating chicken eggs by rotating the eggs in one, two, and three planes. The embryos in eggs that were rotated in two and three planes developed better and the chicks hatched several hours earlier than in eggs that were rotated in one plane as usual. When eggs were incubated in four positions (rotation in two planes), the hatch from eggs with low hatchability increased by 3.1/o, from eggs with average hatchability - by 7-6%, and from eggs with high hatchability - by 4-5%. When turning eggs with good hatchability in three planes, the hatchability increased by 6.4%.
In cabinet incubators, eggs from chickens, turkeys and ducks are incubated in a vertical position. It is advisable to keep large duck eggs in a horizontal or inclined position from the 7th to the 15th day of incubation. Geese eggs are incubated in a horizontal or inclined position. Turning of eggs begins immediately after laying in the incubator and ends when they are transferred to hatching or one day earlier. The eggs are turned every two hours (12 times a day). When positioned vertically, the eggs are rotated 45° to either side of the vertical position. Eggs in a horizontal position are also rotated 180° once or twice a day.

How long is the period during which a hen hatches eggs (chicks)? Incubation lasts 21 days. During this time, it is necessary to monitor embryonic development three times using an ovoscope. During this process, the quality of the embryos and the conditions of incubation are determined. Chicken eggs are examined on the 7th, 11th and 18th day from the moment the chicken began to hatch eggs.

At first viewing, the developing embryo should not be visible, only its shadow and well-developed blood vessels on the yolk. A poorly developed embryo is clearly visible near the shell; in a dead embryo, the vessels are dark, in the form of a ring. Unfertilized eggs are visible as completely light.

Development of a chicken embryo in an egg

On second examination, well-developed embryos are visible as a network of blood vessels on a bright field. The shadow of the embryos makes up a fourth part.

On the third viewing, the embryos are visible as a dark spot. At the blunt end of the egg, their movements can be observed.

After each inspection, rejected eggs should be selected and the remaining eggs should be placed closer to the center of the nest.

Every day of incubation of the eggs of any bird is accompanied by various changes in the embryo. Understanding what is happening inside the hatching egg will allow the farmer to better understand whether incubation is proceeding correctly, what is normal and what is a deviation. To do this, we will analyze this process day by day.

1 day of incubation of chicken eggs

On the first day of incubation, 2 germ layers are formed. The upper one is ectoderm and the lower one is endoderm. After this, the third - middle sheet - mesoderm appears. Subsequently, these 3 layers participate in the formation of the necessary tissues, organs, and systems. Thus, the ectoderm participates in the formation of: the upper layers of the skin, feathers, comb, earrings, beak, as well as all nervous tissue and sensory organs. The endoderm forms the intestines with glands, respiratory organs, thyroid gland, etc. And the mesoderm is involved in the formation of: muscle tissue, glands and organs of genitourinary secretion. The embryonic disc spreads over the vitelline surface. The light field becomes elongated and forms the image of a pear, the narrow part participates in the formation of the tail part, and the head part from the wide one.

Day 2 of incubation of chicken eggs

On this day, the neural tube is formed, and brain vesicles grow at its end. The heart muscles begin to contract rhythmically, which means the vascular system is working and blood circulation begins. By the end of the day, the yolk circulatory system is actively working.

Day 3 of incubation of chicken eggs

The heart pulsates intensely, the pulse rate is directly related to the temperature of the environment around the embryo.

4th day of incubation of chicken eggs

On this day, you need to monitor the incubation process using an ovoscope. During ovoscopy, the vessels of the circulatory system of the yolk circle will be visible. Whether the embryo grows correctly and whether development proceeds intensively depends on this. The yolk is in the shape of an ellipse.

Day 5 of incubation of chicken eggs

The head section is significantly superior in height. When ovoscoping on the 5th day, the pigmented retina should be visible. Allantois spreads greatly. Hematopoiesis occurs in the liver. The primary kidney increases its size and takes on the function of excreting waste products

Days 6 and 7 of incubation of chicken eggs

During this period of time, muscle tissue contracts and he can move. The respiratory organs and digestive system begin to form, and the eyelids are formed. A blood network appears on the surface of the allantois. The yolk remains almost unchanged; before this, it increased in size for six days. This happens because the embryo consumes the liquid layer more intensively, and its filling does not proceed as quickly.

Days 8 and 9 of incubation

Metabolic products accumulate in the allantois cavity.

10th day of incubation

On this day, the heating in the incubator is reduced, since heat is independently released from his body. Water must be removed from the allantois, so the humidity in the incubator is reduced and monitored to ensure that overheating does not occur. Starting from the 10th day, the source of nutrition and the way breathing changes in the embryo. There is a large amount of liquid in the amnion, the fetus swallows it and then it is absorbed in its digestive tract.

11th day of incubation

The resulting network of vessels grows at high speed under the shell, it captures the remaining protein at the sharp end and the allantois closes.

Days 12 and 13 of incubation of chicken eggs

When ovoscoping, the rudiments of the ridge are visible, which looks like a protrusion with a faint outline of the ridge teeth. The rudiments of feathers on the wing are clearly visible, and there is eye pigment. All these signs indicate a normal course of incubation.

14th day of incubation of chicken eggs

During this period, the amnion is stretched due to the large size of the embryo and due to the constant supply of protein. The protein is used by the embryo intraintestinally, the glandular section of the stomach and pancreas begin to actively function. The embryo is large, moves and is completely covered with down.

15-19 days of incubation of chicken eggs

During this period of time, all functions and organs are fully formed.

20th day of incubation of chicken eggs

On the 20th day of incubation, the eggs should be transferred to hatching trays. During this period, the embryo's method of gas exchange changes. The allantois no longer serves as a source of respiration; this function is taken over by the lungs. This transition between different ways of breathing is necessary and difficult. At this moment, it is necessary to increase the humidity in the incubator and ensure good air exchange. This will ensure excellent and timely chick hatching. At the beginning of the 20th day, the yolk sac is completely retracted. The chicken's neck arches, causing the air chamber to become tortuous.

21 days of incubation of chicken eggs

If everything went normal during the incubation period, then on the 21st day the chick hatches. At this point it should have: the yolk is completely retracted, the umbilical opening is narrowed and scarred. The chicken pecks at the shell and tries to get out.

The origin of life is the most beautiful and amazing thing on this earth. With the help of an ultrasound machine, we can observe the development of a human embryo and see how every week the twisted embryo turns into what in the future will be called a person. But who can boast of having seen how a chick develops inside an egg and tell what stages of development it goes through before being born? Let's take a look at this amazing process!

The chicken was raised in a Petri dish:

Here it is, the most ordinary chicken egg, but of the very first freshness. Eggs are selected very carefully for the incubator.