What is the function of the air chamber in the egg. Height of the air chamber of a chicken egg
Egg air chamber ANIMAL EMBRYOLOGY
AIR CHAMBER OF AN EGG - a space located at the blunt end of the egg between the inner and outer shell membranes and filled with air.
General embryology: Terminological dictionary - Stavropol. O.V. Dilekova, T.I. Lapina. 2010 .
See what “egg air chamber” is in other dictionaries:
egg air chamber- NDP. egg meadows A cavity at the blunt end of the egg between the inner and outer shell membranes, filled with air. [GOST 18473-88 (CT SEV 6095-87)] Inadmissible, non-recommended meadows eggs Subjects poultry farming ... Technical Translator's Guide
ANIMAL EMBRYOLOGY AIR CHAMBER - an air cavity at the blunt end of a bird egg, which contains reserve air necessary for the development of the chick... General embryology: Terminological dictionary
EGGS- birds are a formed fertilized embryonic cell, equipped with a large supply of nutrients and enclosed in a hard calcareous shell. In the eggs of birds, a distinction is made between the white, the yolk and the shell. Layers of protein in one place... ... Great Medical Encyclopedia
EGG- a female reproductive cell formed in the ovaries of a female. For a layman, the word egg usually means a chicken egg covered with a hard shell and eaten. However, for a biologist, an egg is a specialized cell from which... ... Collier's Encyclopedia
Egg- This term has other meanings, see Egg (meanings). Eggs of various species of birds and other animals An egg, or oocyte, most often, an ovum or embryonic form of an animal ... Wikipedia
Egg female reproductive cell*- (ovum) or female reproductive cell in its finally formed form. When the egg matures in most Metazoa, it is surrounded by a layer of cells that form a shell or follicle around it and are called follicular. But such a layer may not exist.... ...
Egg- (ovum) or female reproductive cell in its finally formed form. When the egg matures in most Metazoa, it is surrounded by a layer of cells that form a shell or follicle around it and are called follicular. But such a layer may not exist.... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron
Ovoscope- (from Latin ovum (ovum) “egg” and Greek σκοπεῖν (scopeine) “to examine, look”) a device for determining the quality of eggs by candling them. The illumination source (lamp) is located inside the housing with oval holes in the shape ... Wikipedia
Egg dishes- The most elementary, the most ancient of all egg dishes is a raw egg, drunk in one fell swoop, and later beaten with honey or sugar and a teaspoon of cognac or vodka (modern eggnog). Raw eggs are used as a dish... ... Great Encyclopedia of Culinary Arts
Siphonophores- (Siphonophora) order of the class polypomedusae (see), or Hydrozoa, type coelenterata (Coelenterata). S., which are free-swimming polymorphic colonies (see Colonies), are exclusively pelagic marine animals, distinguished by... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron
Bird eggs are closed life support systems for developing embryos. A newly laid egg contains all the necessary nutrients, mineral salts, energy sources and water, so it only needs heating and periodic rotation, which prevents the embryo from sticking to the shell membranes. The egg lacks only one important component of metabolism - oxygen, which is necessary for metabolic processes to occur in the cells of the embryo, which are the basis for normal development. How does the embryo in the egg receive oxygen from the surrounding atmosphere and release carbon dioxide outward, in other words: how does the egg breathe?
Gas exchange is usually associated with periodic inhalation of a mobile medium (air or water), in which oxygen is delivered to the capillaries of the lungs or gills and carbon dioxide is carried away with each exhalation. The speed of movement of the medium through the gills and lungs depends on the intensity of the work of special muscles under the control of the nervous system and determined by the metabolic needs of the body. However, respiratory movements are not typical for the eggs of birds and other animals (for example, insects, arachnids, amphibians and reptiles); they lack air flows that could deliver oxygen to the capillaries of the embryo. However, bird eggs “breathe,” and this “breathing” is accomplished by the diffusion of gases through thousands of microscopic pores in the shell.
These pores were first discovered in 1863 by John Davy, a member of the Royal Society for the Advancement of Science and Letters of Edinburgh, without the aid of a microscope. He immersed the egg in a vessel of water and, using a vacuum pump, pumped out the air from it. At the same time, small bubbles formed on the surface of the shell. Davy came to the conclusion that the shell was pierced by tiny channels.
The movement of gases through pores is described by the laws of passive diffusion: from an area of high concentration, molecules tend to move to areas of low concentration of a given substance. Diffusion occurs only due to the kinetic energy of gas molecules and does not require direct energy expenditure from the embryo; The lower concentration of oxygen inside the egg causes molecules to rush in through the pores from the atmosphere, where the partial pressure of this gas is higher. Conversely, a significant content of carbon dioxide inside the egg leads to an opposite flow of carbon dioxide molecules. The intensity of diffusion processes depends on the length and total cross-sectional area of the pores, as well as on the difference in the concentrations of diffusing gases inside the egg and in the atmosphere.
The concentration of water vapor in the air chamber inside the egg is higher than outside, and water molecules (they are smaller in size than oxygen molecules) also diffuse out. In the process of evolution, animals have developed numerous adaptations for conserving water, while bird eggs secrete it at a controlled rate. The source of energy for the developing embryo is mainly the fats stored in the yolk, and when each gram of fat is broken down, almost the same amount of water is released. Therefore, if water is not removed from the egg, its relative content will increase during incubation. In order for the relative water content at the moment of hatching to be equal to its content in the newly laid egg, about 15% of the initial mass of the egg must be lost in the form of water vapor. Poultry breeders are well aware that the loss of this amount of water is necessary for normal hatching.
Over 21 days of incubation, an “average” chicken egg, initially weighing 60 g, consumes about 6 liters of oxygen and releases 4.5 liters of carbon dioxide and 11 liters of water vapor. Due to water loss, by the end of incubation the egg weighs about 51 g, and the newly hatched chick weighs about 39 g (the remaining weight is the shell and two membranes).
Three egg membranes - the shell and two subshells - are known to everyone who has ever peeled a boiled egg. All three shells form in less than 24 hours as the egg moves through the hen's oviduct into the "womb." The outermost layer of the egg shell is called the cuticle (absent in some species) and is a thin film of organic matter, often with cracks through which the shell itself appears. The shell consists of calcium carbonate, represented by columns of calcite crystals, and a small amount of organic matter. Due to the imprecise fit of the columns to each other, voids remain between them, penetrating the entire thickness of the shell and forming microscopic pores.
The inner and outer shell membranes are formed by a network of organic fibers. The outer shell fibers are connected to the inner surface of the shell through mamillary tubercles, which are centers of crystallization during shell formation. Shells differ in the diameter of the fibers that form them, in the network structure and in overall thickness. The inner surface of the inner shell is lined with a thin film, which is an independent formation, and not a simple continuation of the membrane fibers. Soon after the eggs are laid, the spaces between the fibers in the shells fill with air.
Pores in the shell are the only possible way for gas exchange between the tissues of the embryo and the environment. They have a cylindrical shape and, where they come to the surface, are often hidden by particles of secreted organic and inorganic substances. If the shell is carefully etched with acid and then painted, then the pores can be seen with the naked eye: in the shell of a chicken egg there are up to 10,000 of them. The size and number of pores are determined in the shell gland and do not change in the future. As will be seen from the following presentation, the shape and size of the pores, as well as their number, vary in different species of birds, and the possibilities of gas exchange through the shell are determined precisely by the geometry of the pores.
Since the developing embryo cannot control gas exchange processes, the permeability of the shell and subshell membranes for gases must precisely correspond to the metabolic needs of the embryo. If the permeability is too high, the oxygen needs of the embryo will be fully satisfied, but excessive loss of water can lead to dehydration of the egg; if it is too low, the embryo will die either from a lack of oxygen or from an excess of carbon dioxide and water formed as a result of metabolism. Therefore, to ensure the optimal partial pressure of gases in the egg and the desired rate of water loss, a “golden mean” must be achieved in the size and number of pores.
Throughout the entire incubation period, water is removed from the egg at a constant rate, and the oxygen consumption of the embryo increases significantly. In a chicken, the first 18 days of incubation are called the prenatal period. On the 5th and 6th days, the chorioallantois (the respiratory organ of the embryo, similar to the placenta of mammals) connects with the lining of the inner shell membrane, and a network of capillaries is formed in it. By the 9th day, the chorioallantois occupies about half of the inner surface of the shell, and by the 12th day, the entire surface (the outer and inner subshell membranes lie between the chorioallantois and the shell).
In the prenatal period, gas exchange occurs through the chorioallantois. The egg gradually loses water, and since the shell is hard, the evaporated water is replaced by gas, which forms an air chamber at the blunt end of the egg. The size of the chamber gradually increases, and by the end of incubation it already occupies about 15% of the egg’s volume. The air chamber directly passes into the spaces between the fibers of the subshell membranes. This can be demonstrated as follows. If, after placing an egg under water, you introduce air under pressure into the chamber, then gas bubbles will appear on the entire surface of the shell at the points where the pores exit. The pressure in the air chamber is practically the same as the air pressure in the shell membranes, which makes it especially convenient for taking gas samples from eggs.
During the first week and a half of incubation, oxygen consumption by the embryo increases slowly. From the 10th to the 14th day it increases sharply, reaching a level of 600 cm3 per day, and does not change until hatching. This value corresponds to the maximum amount of oxygen that can penetrate through the pores in the shell by passive diffusion. Such an amount of oxygen per day (600 cm3) may not seem too impressive to the reader who consumes the same amount of oxygen in two minutes, but for such a volume of gas to enter the egg, an extremely intense flow of molecules is required through all 10,000 pores. In a second, 2 penetrates through each pore into the egg. 10 to the 13th power of oxygen molecules, and 1.4 comes out. 10 to the 13th power of carbon dioxide molecules and 1.2. 10 to the 13th power of water vapor molecules.
During hatching, however, the chick needs more oxygen than the diffusion process through the pores can provide. Where does the extra oxygen come from? Nature provides the simplest solution to this problem: on the 19th day of incubation, the chick pierces the air chamber with its beak. This process is called “membrane puncture”. After this, the chick begins to breathe air from the chamber, ventilating the previously inactive lungs. Puncture of the membrane is very important for the chick, as it allows it to breathe with its lungs and deliver oxygen to the tissues through the bloodstream. The period of active breathing from the air chamber is called the paranatal period, since the chorioallantois is still functioning at this time. Breathing at this stage is carried out, therefore, on the basis of two mechanisms - diffusion and convection.
Approximately 6 hours after the air chamber is punctured, the chick uses an egg tooth to make a small hole in the shell and for the first time begins to breathe directly into atmospheric air. By this time, the lungs are already functioning well enough to provide the chick with oxygen during the upcoming hard work - breaking the shell. During this period, the role of the chorioallantois in the respiration process begins to decrease, although it persists until the chick breaks free from the egg and leaves the egg membranes stuck to the inner surface of the shell. A smooth transition from passive to active gas transport takes from 24 to 36 hours.
It is now known that there are several obstacles on the path of oxygen from the atmosphere to the capillaries of the chorioallantois, namely the shell, as well as the inner and outer shell membranes. Specialists involved in the physiology of respiration characterize the permeability of membranes to gases by such a parameter as conductivity - the reciprocal value of the resistance that the membrane has to diffusing gases. Partial pressures of gases in the blood are usually expressed in torrs, or millimeters of mercury. One torr is equal to 1/760 of normal atmospheric pressure, i.e. the sum of the partial pressures of all gases in the atmosphere (nitrogen, oxygen and carbon dioxide) at sea level.
There is a difference of approximately 100 mmHg between the partial pressures of oxygen in the atmosphere (154 mm Hg) and in oxygenated blood in the vessels of the chorioallantois (58 mm Hg). Art. This pressure is 58 mmHg. Art. almost enough to saturate the blood with oxygen, which is then distributed to all tissues of the embryo. The oxygen pressure in the venous blood returning from the fetus is 22 mmHg. Art. Flowing through the chorioallantois, it is again saturated with diffusing oxygen, and the partial pressure of oxygen reaches 58 mm Hg. Art. The partial pressure of carbon dioxide, on the contrary, drops from 47 mm Hg. Art. in venous blood up to 38 mm Hg. Art. in oxygenated.
Determining the gas conductivity from the inner shell to the chorioallantois has proven to be an extremely difficult task, since the partial gas pressure in the air chamber and in the oxygenated blood must be measured simultaneously. This was done by an employee of Yamagata University, H. Tazawa.
To measure the partial pressure of oxygen and carbon dioxide in the egg, Tazawa mounted a hypodermic syringe on the shell above the air chamber, partially filled with air that was in contact with the air in the air chamber. After a few hours, the partial pressures of oxygen and carbon dioxide in the syringe and in the air chamber were equalized. Thus, by measuring the partial pressure of gases in the syringe, it was possible to determine these values for the air chamber. Tazawa measured the pressure of gases in oxygenated blood using a thin plastic catheter inserted through a hole made in the shell into the chorioallantoic vessel, through which oxygenated blood flows to the embryo. When determining the oxygen and carbon dioxide content, air samples from the syringe and blood from the vessel were taken simultaneously.
Using the described technique, Tazawa found that the partial pressure of oxygen in the air chamber was 50 mm Hg. Art. higher than in arterial blood, and carbon dioxide - by 2.5 mm Hg. Art. below. The fact that the oxygen pressure in the chamber is 50 mm Hg. Art. differs from the pressure in oxygenated blood, requires a special explanation. It is unlikely that this difference can be associated with the presence of air spaces between the fibers of the inner subshell membrane. Rather, it may be due in part to the fact that a thin, continuous film separating the inner shell and the chorioallantoic epithelium prevents the diffusion of gases. Another possible explanation is that part of the venous blood (its partial pressure of oxygen is 22 mm Hg) bypasses the capillary network in which gas exchange occurs and mixes with oxygenated blood, reducing the oxygen pressure in it to 58 mm Hg. Art. Naturally, these explanations are not mutually exclusive.
Tracing changes in the partial pressure of oxygen along the path between the atmosphere and oxygenated blood leaving the chorioallantois, it is clear that significant pressure drops occur only in two places: the shell itself and the inner subshell membrane. However, the difference in the partial pressures of carbon dioxide and water vapor is due only to the shell.
If a specialist in respiratory physiology is given the task of developing the principle of an effective gas exchange system, he will try to maximize its permeability to oxygen. In the egg, such purely respiratory considerations should not conflict with other factors important for the survival of the embryo. In particular, the shell must be thick enough to provide mechanical protection to the embryo, prevent the penetration of bacteria, preserve the liquid environment of the egg and maintain the carbon dioxide pressure necessary for normal acid-base balance.
How does this process occur in the most diverse eggs of the remaining 8.7 thousand species of birds? A quarter of a gram is the weight of the smallest known eggs laid by one of the hummingbird species; they are 240 times lighter than a regular chicken egg. At the other extreme is the egg of the recently extinct Madagascan bird Aepyornis, which weighed 9 kg; it is 150 times heavier than chicken. The egg shell of this bird alone weighed about 2 kg, i.e. half a kilogram more than the entire egg of the African ostrich, which holds the record for the mass of eggs laid among living birds.
How do the shapes and sizes of pores in the shells of large and small eggs differ? To answer this question, Cyril Tyler and K. Simkiss impregnated the shells of different eggs with plastic. The shell was then dissolved to create microscopic plastic impressions of the pores. The study of such casts showed that even within the same species, the shape and size of the pores vary noticeably.
Gas exchange through the shell occurs exclusively by diffusion. The movement of gas through a permeable barrier due to diffusion depends on the chaotic movement of gas molecules and the difference in concentrations of the diffusing substance on different sides of the barrier. Gas molecules will move from an area of high concentration to an area of low concentration due to the fact that collisions between them are more frequent at high concentrations.
In general, the amount of gas that diffuses per unit time through the pores in the shell is directly proportional to the area of the pores available for diffusion and the difference in the concentrations of this gas on both sides of the shell. At the same time, the diffusion rate is inversely proportional to the length of the diffusion path (in this case, the axial length of the pore). In other words, the permeability of the shell for gases is determined by the ratio of the pore lumen area to its length. Doubling the cross-sectional area of the pores or the difference in gas concentrations will lead to a doubling of the diffusion rate, while doubling the thickness of the shell, with other parameters remaining constant, will halve the rate of gas penetration. Thus, if it were possible to measure the gas flow and divide the resulting value by the difference in gas concentrations, then it would be possible to determine the permeability of the shell for this gas.
If the eggs are kept in a desiccator at a constant temperature and removed briefly for weighing only once a day, their mass decreases at a constant rate over many days. The weight loss is entirely determined by the evaporation of water through the pores into the dry atmosphere of the desiccator. Dividing the daily weight loss by the difference in water vapor pressure between the outside and inside of the egg gives the permeability of the shell to water vapor. Knowing this value and taking into account that the diffusion paths for water vapor, oxygen and carbon dioxide are the same, it is easy to calculate the permeability of the shell to oxygen. Determining the permeability of the shell to oxygen in this way is quite easy: for this you only need to have a desiccator, an accurate scale and a thermometer.
If you add calipers to these tools, you can also measure the thickness of the shell, equal to the length of the pore. Knowing the permeability and pore length, it is possible to calculate the effective pore area - the sum of the cross sections of all pores through which diffusion occurs. (10,000 pores of a chicken egg have a total cross-sectional area of 2 mm2).
It is also interesting to note that with an increase in egg mass by an order of magnitude, the pore length increases by only 2.7 times. Perhaps this dependence is explained by the balance of adaptive factors during evolution. The thickness of the shell (on which the length of the pores depends), on the one hand, is determined by the fact that the shell must withstand the pressure of the contents enclosed in it and the brooding bird, but, on the other hand, it is limited by the ability of the chick to break through the shell upon hatching. The last factor, apparently, can serve as an explanation for the nonlinearity of the dependence of shell thickness on egg size.
The structural characteristics of the shell (pore area and their length) determine its permeability. This functional property can be correlated with the metabolic needs of the embryo and with the difference in partial pressures of oxygen on different sides of the shell. There is a quantitative relationship between these two variables: the difference in partial pressure is equal to the amount of oxygen consumed by the egg divided by the permeability of the shell to this gas.
Let's use as an example a hypothetical egg that consumes 10 ml of oxygen per 1 mmHg per day. Art. (i.e., for every millimeter of mercury column of partial pressure difference on different sides of the shell, 10 ml of oxygen diffuses through it per day). If the embryo in the egg consumes 500 ml of oxygen per day, then the difference between the internal and external partial pressures should be 50 mm Hg. Art. Based on the fact that the partial pressure of oxygen in the atmosphere is close to 150 mm Hg. Art., it can be calculated that the pressure of this gas in the air chamber (with which the fetal blood is in contact) will be equal to 100 mm Hg. Art., or 14%.
We explore the connection between shell permeability and embryo metabolism. To do this, using material from 28 species, we compare the oxygen consumption of the egg immediately before puncture of the membrane with the permeability of the shell for oxygen. Extensive data on the oxygen consumption of eggs of many species, large and small, was obtained by three researchers from the University of California at Los Angeles: Donald Hoyt, David Vlack and Carol Vlack. Knowing the amount of oxygen consumed by the egg and the permeability of the shell, the partial pressure of oxygen in the air chamber can be calculated. This value turns out to be approximately the same for eggs of all 28 species studied: about 105 mm Hg. Art., or 15%. The results obtained were confirmed by taking control air samples directly from the air chambers of eggs of 13 species. In addition, the partial pressure of carbon dioxide is 35 mm Hg. Art., or 5%.
The pressures of oxygen and carbon dioxide in the air chamber of the egg before the membrane is punctured are almost the same as in the lungs of adult birds. Consequently, the permeability of the shell to oxygen guarantees the necessary rate of its entry into the egg, which in turn is related to the metabolic needs of the embryo immediately before the membrane is punctured. In addition, the permeability of the shell provides the same partial pressure of oxygen and carbon dioxide in the air chamber as in the lungs of an adult bird. A. Vischedijk from Utrecht University suggested that such gas concentrations are important for initiating the activity of the chick at hatching and preparing it for the postnatal period of life.
The remarkable thing is that the permeability of the shell very accurately corresponds to the mass of the embryo. As a result, the final concentrations of oxygen and carbon dioxide are almost the same in eggs of a wide variety of sizes. The versatility of the functioning of the shell as a gas conductor is even more impressive when you consider that the incubation time of eggs can vary from 11 days (some small species) to 70 days or more, like the wandering albatross.
Until now, the patterns of evaporation of water by an egg, which occurs uniformly throughout the entire incubation period, have not been examined in detail. Water loss does not depend on the metabolic rate of the embryo, but is a necessary condition for normal hatching. The reasons for this are not completely clear, but it is assumed that they have to do with the state of hydration of the fetal tissues.
The connection between the amount of water evaporated and the mass of the egg was first established by Rudolf Drenth from the University of Groningen. The data he obtained for 45 species indicate that with an increase in egg mass by 10 times, the amount of water evaporated daily increases by 5.6 times.
The cavities of the egg are essentially saturated with water vapor, the pressure of which at the common incubation temperature for most species (35.6 ° C) is 44 mm Hg. Art. For normal evaporation processes, the water vapor pressure in the nest must be maintained at 15 mmHg. Art., which corresponds to a relative humidity of 45%. Such humidity can only be ensured through constant ventilation of the nest and the influx of dry air from outside. It is not known how birds determine the humidity in the nest, but by changing their behavior, they are able to regulate the outflow of water vapor into the surrounding atmosphere. Consequently, during the incubation period, parents perform two main functions: they ensure the optimal temperature of the eggs and maintain the humidity in the nest within the required limits.
The duration of embryonic development, or incubation time, is probably determined genetically, and the metabolic rate of the embryo must correspond to the length of the incubation period so that at the end of incubation (regardless of its duration) the embryo is able to hatch and survive. From this we can conclude that the geometry of the shell pores (and, consequently, the permeability of the egg shells to oxygen) is associated not only with the mass of the egg, but also with the duration of incubation.
The correspondence of the properties of the egg shells to the needs of the embryo's respiration is beyond doubt, although the evolutionary development of this basic function allowed for some compromises with the tasks of mechanical protection of the egg and maintaining the water and acid-base equilibrium of the developing embryo. Bird eggs are an ideal model for studying diffusive gas exchange. Such a model may also be useful for analyzing more complex processes occurring in the human respiratory tract and lungs.
To successfully breed various breeds of chickens, many farmers use incubators. With their help, you can get the required number of chickens within the planned time frame. But to obtain healthy offspring and maximum hatchability, you need to understand how chicken eggs are incubated.
The ideal situation is when the chicken hatches her eggs on her own. But you can only get up to 15 chicks from one hen. This amount is not enough even for household farming. Therefore, incubators come to the rescue of poultry farmers.
In ordinary home units, the temperature is not the same, so experts advise mixing the eggs daily, moving the outer ones to the center and vice versa. Humidity is regulated by pouring water into special gutters or placing containers with water inside.
The hatching process requires constant monitoring: the farmer has to monitor temperature, humidity, provide air access and periodically cool the testicles. Otherwise, problems cannot be avoided.
Possible problems
Even before laying, poultry farmers should become familiar with the consequences of non-compliance with incubation rules.
But the reasons for poor hatchability lie not only in non-compliance with the recommended regimens. It is important to use only high quality eggs.
Selection of raw materials for incubation
For laying, experts advise taking fresh eggs that have lain for no more than 7 days from the moment of laying to the planned laying date. The hatchability and survival rate of chickens depends on their storage conditions. After all, if they are in an unfavorable environment, then the rate of their aging increases. The temperature and humidity of the surrounding air are important.
Only those specimens that have passed a special selection are taken for bookmarking. What matters is their mass, type and shape of the shell.
Egg selection rules
Poultry farmers select eggs from laying hens with high productivity. This increases the likelihood of getting healthy offspring. Before incubation preparation, all additives that increase egg production are removed from the chickens’ diet. The food is made as natural as possible.
Knowledgeable people do not advise incubating specimens that are too large. This is due to the fact that they:
- reduced level of hatchability (this was established experimentally);
- thin shell.
Important! If a large number of large eggs are placed in the device, then there is little space between them, which means that the ventilation process worsens. It has been experimentally established that large testicles more often produce disabled chicks.
Small specimens weighing less than 52 g are also rejected. The mortality rate of already hatched chicks reaches 38%.
Storage of raw materials
If short-term storage is planned, then storing raw materials in a room with a temperature of up to 20°C is allowed. But it should be there for no more than 5 days. The optimal storage period is considered to be 2 days. Humidity is maintained at a fairly high level: 75% is considered optimal.
- when they are in a vertical position, a revolution is carried out from the sharp end to the blunt one;
- when horizontal, they are turned 180°.
This helps prevent the yolk from moving and drying out, and minimizes the likelihood of stretching and tearing off the dense protein strands that hold the yolk in the center.
Notice! If long-term storage is required, then the eggs are packaged in special moisture-resistant and gas-tight packaging. These can be lavsan or lavsan-polyethylene bags that close hermetically. They are placed in rooms with a temperature of about 10-12 °C. This way the shelf life can be increased to 2 weeks.
You can understand how much hatchability decreases when stored under standard conditions by looking at the table.
Chick hatchability
Selection using an ovoscope
One of the best methods for rejecting low-quality specimens is to examine them with an ovoscope. It allows:
- identify small cracks, depressions, growths and other shell defects;
- estimate the size of the air chamber: permissible thickness is 2-4 mm (the smaller it is, the younger the egg);
- understand the location of the yolk, check whether it has stuck to one edge and does not move during sharp turns;
- see a “marbled” shell (this defect indicates a lack of calcium);
- identify dark spots indicating mold damage;
- see blood clots and foreign objects (grains of sand, feathers);
- specify the number of yolks (double-yolk specimens are not suitable).
For successful hatching, it is not enough to choose the right material for incubation; it is important to familiarize yourself with the main nuances of the laying.
Rules for laying eggs
Having selected the best eggs, the farmer begins incubation. Initially, you should bring the prepared raw materials into a warm room for preheating. It is necessary to ensure that the temperature of the eggs reaches 25°C.
Some say that washing eggs is prohibited. But experienced poultry farmers insist that cleaning and disinfection are mandatory. For these purposes, use a pale solution of potassium permanganate or 1.5% hydrogen peroxide. Use a soft cloth soaked in disinfectant liquid to wipe the shell. Some people advise simply soaking them in a container with a solution for a few minutes, placing them on a dry, clean cloth and waiting for them to dry completely. The optimal temperature value for the solution is 30°C.
Depending on the incubator model, horizontal or vertical laying is carried out. This will determine how the testicles will have to be turned over in the future:
- in a horizontal position they are rotated 180°;
- in the vertical – tilted 45° in different directions.
Important! Experts say that horizontal laying is preferable. It is in this position that the hen incubates them. The embryo rises as high as possible, approaching the heat source.
In ordinary home units, a horizontal placement method is provided. In industrial machines with automatic inversion, the testicles are placed vertically so that the blunt end points upward.
When laying, keep in mind that each additional gram of weight increases the time until hatching by 40 minutes. Therefore, experts advise choosing eggs with approximately the same mass. But you can do it differently.
- The largest specimens are stacked first.
- After 4 hours, medium eggs are placed in the incubator.
- 8 hours after the first, the laying of the smallest eggs begins.
Attention! Experienced poultry farmers say that the optimal period for starting incubation is the evening (about 18 hours). In this case, the peeling begins in the morning of the 21st day. Until the evening, the bulk of the chicks are born.
The incubator itself is also pre-washed, disinfected and warmed up to operating temperature.
Bookmarking begins when the thermometer shows more than 36°C. Proper organization of the process of laying raw materials is only one of the components of success. It is important to understand how to incubate the raw material and what conditions should be followed.
Chick incubation process
Even before placing the selected eggs in the incubator, it is necessary to understand the process. Incubation lasts 21 days, but hatching can begin on days 20-22. If hatching has not started before day 24, then there is no point in waiting any longer.
Conventionally, the entire process is divided into several periods: in each of them, humidity and temperature should be adjusted. Compliance with the required conditions is the key to the maximum percentage of hatching and production of healthy chickens. After all, the success of the process depends on the microclimate in the hatchery chamber.
Video - Instructions for incubating chicken eggs
Instructions for keeping future chickens
You can get full-fledged offspring if you figure out at what level the temperature and humidity should be maintained. Separately, poultry farmers will have to figure out how to organize the process of ventilation and cooling of the future brood of chicks. Step-by-step instructions will help you understand the nuances of the process.
Step 1. After laying the raw materials, the first period begins. It lasts 6 days. At this time, humidity is maintained at around 65%, temperatures at 37.5–37.8°C. Turn the testicles up to 6-8 times a day. In exceptional cases, it is allowed to increase the intervals between coups, but they should not exceed 12 hours. Please note that under natural conditions in the nest the hen moves them almost hourly.
Step 2. The second incubation period lasts from 7 to 11 days. Humidity during this period decreases to 50%, the temperature remains 37.5 – 37.7°C. The periodicity of testicular rotation is maintained.
Step 3. From 12 to 20 days there is a 3rd incubation period. Temperatures drop to 37.5°C. At the same time, the humidity rises to 75%; for these purposes it is recommended to regularly spray the testicles. Starting from day 18, it is necessary to ensure air flow and periodic cooling. Twice a day the incubator is opened for 15 minutes to cool the future chicks. From the 19th day, the upheavals stop, and there is no longer any need to disturb the mature chicks.
Step 4. The final stage begins on days 20-21. The chicks begin to hatch. The humidity inside the incubation chamber should be high and the temperature should be kept at 37.2°C. Experts advise taking the hatchlings out of the incubator after drying.
You can quickly figure out what conditions should be created for the future brood using a table.
Temperature and humidity by period
Video - Features of incubation temperature conditions
Knowledge of the technology and features of hatching offspring using special devices allows you to obtain the maximum percentage of healthy chicks hatched.
Secrets of the incubation process
- To hatch chicks, only high-quality raw materials are selected: any cracks or chips will cause loss of moisture and stop the development of the embryo. Irregularities on the shell, growths, and defects indicate a lack of nutrients.
- Before laying the apparatus, in which the revolution is carried out manually, you should make marks on the shell: draw a stripe or a cross on one side, and a circle on the other. They will help you understand whether the poultry farmer turned over all the testicles.
- Turning of eggs up to the 19th day is carried out more than 4 times a day - this minimizes the likelihood of the embryo growing to the wall. Experts advise doing revolutions at regular intervals.
- Particular importance is paid to controlling humidity and temperature indicators. Failure to comply with the established regimes is the main cause of death of formed embryos.
Timely rejection of eggs allows you to ensure the production of healthy offspring. Problematic specimens can be detected using periodic ovoscoping.
- The first candling is carried out before setting up the incubator.
- On the 4th day you can see the air chamber located at the blunt end, the beginning of the development of the circulatory system: the vessels are already visible.
- On days 6-7, it is clear that the vessels filled almost the entire internal surface; upon closer examination, movements of the embryo can be seen. Many people recommend candling eggs at this time.
- On the 11th day, the contents under the shell are poorly visible and are darker. In the part that is visualized, vessels are visible.
- On the 19th day there is practically no clearance, only the air chamber is visible. The embryo is already fully developed, but not yet ready to hatch.
Notice! It is not necessary to wait 6-7 days for ovoscopy. 24 hours after laying, the active development of the blastoderm is already visible. The ovoscope will show a darkening that moves when the egg is turned over. Its diameter is about 5 mm.
But not all eggs, when candled, look as described. Those specimens should be rejected if, when scanned, it was revealed that:
- the subshell membrane is exfoliated;
- the air chamber is located not at the blunt end, but on the side;
- instead of blood vessels, bloody spots are visualized or only the yolk and air chamber are visible;
- a blood ring appeared (the embryo died from days 1 to 6 of incubation);
- the fetus is frozen (detected on days 7-14), it looks like a dark spot, blood vessels are not visualized.
Experienced poultry farmers advise getting rid of such eggs in a timely manner. If you follow all these recommendations, you will be able to achieve almost 100% hatching of offspring.
Stages of Chick Development
All chickens begin to develop from the blastodisc - this is the cytoplasm located on the yolk. Fertilized blastodiscs begin to divide during the process of egg formation in the laying hen's body. By the time of laying, it is completely surrounded by blastoderm. If you break such an egg, you will see a whitish spot on the surface of the yolk with a diameter of up to 2 mm.
If after laying the egg finds favorable conditions, the cells continue to divide. The development of the embryo goes through the following stages.
The order of embryo development
| Development | Dates of appearance, days |
|---|---|
| The rudiment of the circulatory system | 2 |
| Pigmentation of the pupils | 3 |
| Limb buds | 3 |
| Allantois formation | 4 |
| Setting the beak shape | 7 |
| Feather dorsal papillae | 9 |
| Completion of beak formation | 10 |
| Closure of the allantois | 11 |
| Appearance of a cannon on the head | 13 |
| Down covering of the chick's body | 14 |
| Completing Protein Usage | 16 |
| Pulling out the yolk (beginning of the process) | 18 |
| Moving the neck into the air chamber | 19 |
| Eye opening | 20 |
| Beginning of the biting process | 20-21 |
Video - The process of development and emergence of a chicken
The appearance of chicks
Pecking of the shell begins from the center. The chickens make a hole for themselves in a circle, breaking off pieces. Then the chick presses on the shell and it breaks. The weight of newborn egg breeds is about 35 g, meat breeds - up to 42 g.
After the hatching process is completed, farmers evaluate the offspring. In healthy chickens:
- closed umbilical cord, traces of blood are not visualized;
- the fluff is bright, soft to the touch and shiny;
- eyes shine;
- the wings are pressed tightly to the body.
After drying, the chicks become active, mobile, and react to any noise.
Common Incubation Errors
To minimize the amount of incubation waste, you can deal with the main mistakes in advance. They are allowed mainly by novice poultry farmers.
- Laying too large or small eggs.
- Incubation of stale raw materials, storage of eggs in unsuitable conditions (in rooms where temperatures are above 20°C, in the refrigerator).
- Placing eggs in an incubator whose shells are contaminated with droppings.
- Use of copies with obvious defects.
- Incorrect setting of incubation modes.
If you select the raw materials correctly, constantly monitor the temperature in the incubator, check the humidity and promptly reject the eggs, then at the end you can get a hatchability close to 100%.
Diagnostics of underheating. Low temperature delays the development of the embryo from the first days of incubation, but does not cause such deep and specific developmental disorders as high temperature. When candling eggs after 6 days of incubation, a general developmental delay is revealed: the embryos are small, lie close to the shell, due to which they are clearly distinguishable, the circulatory system on the yolk is poorly developed, the blood vessels are weakly filled with blood and have a transparent pink color, the embryos are little mobile.
The embryos die late. Blood rings are small and pale. Opening the eggs shows underdevelopment of the membranes and anemia of the embryos (G.K. Otryganyev and G.I. Krylov).
When underheated, the growth of the allantois is greatly delayed and the closure of its edges occurs with a great delay. Therefore, when candling eggs after 11 days of incubation, it is found that the allantois is closed in less than 50% of the eggs.
I. Ya. Pritsker points out that when underheated, chicken fluff develops worse than at normal incubation temperatures or when overheated. During candling before hatching, a general lag in the development of the embryo is also visible: it is small, does not fill the egg, which is visible both at the sharp end and at the air chamber; the latter is small in size; protrusion of the neck into the air chamber occurs with great delay.
Pecking of the shell begins uncomfortably and also with a great delay, but in the proper place, and the shell breaks off in large pieces.
The withdrawal is not amicable and lasts a very long time, sometimes several days. The hatched young are well pubescent. The umbilical ring is well healed and has no scars. The residual yolk is in most cases small. The hatched young are very little mobile, lethargic, stand poorly and unsteadily on their feet. The shell remaining after hatching has a pale pink or light cream color due to the weak filling of the allantois vessels with blood (I. Ya. Pritsker).
With very strong and prolonged underheating, hatched chickens have a large residual yolk sac, often suffer from diarrhea, the shells remaining after hatching are dirty, damp, with unused protein (G.K. Otryganyev).
At the end of hatching, many eggs remain with pecks and living embryos, which are weak and cannot break the shell to get rid of it. Attempts to assist them during hatching lead to hemorrhages from the vessels of the allantois and the death of the embryos.
When opening eggs with dead eggs, it turns out that there are many living embryos in eggs without pecking. Most of the embryos are fully formed, with retracted yolks and used protein; on the head and neck they have large swelling, often hyperemic and with hemorrhages.
Only with very strong underheating does the yolk remain uninvolved and the white unused. When underheated, the yolk sac is pale, the umbilical ring is not closed, and the protein is most often cloudy, with a liquid consistency. Very often the entire yolk or individual sections of it are bright green.
When opening the dead bodies, anemia of the internal integuments and organs can be observed. The intestines are full of yolk and feces, especially the rectum, the diameter of which sometimes reaches the thickness of a finger, the liver is enlarged (G.K. Otryganyev). The heart is enlarged (E. F. Lisitsky) and anemic (I. Ya. Pritsker) (Fig. 3, a).
Rice. 3. a - opened choke when underheated, b - pecking of the shell at high humidity, c - pecking of the shell at low humidity, d - opened choke at high humidity
Humidity disturbance. The relative humidity of the incubator air has a significant impact on metabolism and embryo development. It regulates the evaporation of water from the eggs during the longer incubation period and regulates heat transfer.
Humidity, unlike temperature, the effect of which is felt almost simultaneously with the onset of influence, has an effect more slowly and requires a certain time for its appearance. However, gradually accumulating, the adverse effects of humidity deviations from the norm are very great and are not always correctable.
Diagnosis of high humidity. In the first days of incubation, high humidity does not have a negative effect on the development of the embryo.
When dirty eggs are incubated at high humidity, both in the first days and throughout the entire incubation period, putrefactive processes may develop in the eggs and “cuffs” may appear.
High humidity after the 6th day of incubation begins to retard development, and therefore the closure of the edges of the allantois is delayed.
A slight increase in embryo mortality under the influence of high humidity on average days of incubation is not accompanied by any specific signs of disturbances. There is a general lag in the growth and development of embryos and their membranes. The air chamber is characterized by a small size due to insufficient weight loss by eggs (less than 0.7-0.6% per day).
The appearance of eggs when candling before hatching is very similar to the appearance of eggs incubated under subheating. The air chamber is very small; protrusion of the neck by the embryo does not begin. Large gaps at the sharp end of the egg and at the air chamber indicate significant amounts of amniotic fluid.
The onset of biting is delayed (up to 21 days) and proceeds unevenly. The undershell membrane turns brown after pipping, and often after this further pecking stops due to the death of the embryo.
According to E.E. Penionzhkevich and N.M. Shklyar, high humidity causes a characteristic form of “pecking with liquid release.” This liquid quickly dries and closes the hole in the shell and the embryo dies. The liquid can stick the beak of the embryo to the shell, which will lead to the cessation of the movement of the embryo and its death (G.K. Otryganyev). Attempts to assist with hatching usually cause bleeding and death of the embryo (Fig. 3, b). In hatched young animals, the down, especially around the umbilical cord and anus, is usually dirty. The pigmentation of the limbs and down is very weak. Chicks are lethargic, little active; Their belly is very large, but it can also be soft, due to the retraction of a large liquid yolk.
The death of most unhatched chicks occurs at the moment of pipping, from choking on amniotic fluid. When the asphyxiations are opened, there is an abundance of sticky mucus in the fruit shells, an overflow of fluid in the intestinal tract, the lungs are hyperemic and do not contain air.
In dead embryos, swelling of the neck and head and a large swollen goiter filled with fluid are observed.
Other damage to internal organs is the same as with underheating.
Diagnosis of low humidity. Very low air humidity in the first days of incubation causes a slight increase in embryo mortality, but does not lead to the appearance of any specific damage to them. Low humidity increases the manifestation of signs of overheating at elevated temperatures (G.K. Otryganyev and E.N. Kuchkovskaya).
The egg loses a lot of weight (more than 0.5-0.6%), and the air chamber quickly increases in volume. The allantois may close prematurely.
During candling of eggs before hatching, a slightly accelerated development of many embryos is revealed; there are few dead embryos.
Biting and hatching begin ahead of schedule. The shell shells are very dry and durable. The embryo, breaking through the shell, is not able to break the subshell membranes, from which pieces of the shell fall off. It can make a full circular motion and not be freed from the shell.
After pecking the shell, the fluff dries very quickly. Even a small area of fluff dried in the shell on the body of the embryo interferes with its movements, and sometimes the movements stop and the embryo dies.
Withdrawal is difficult and slow. Hatched chicks are small, poorly pubescent, but mobile. Their fluff is intensely pigmented. When opening eggs with dead eggs, you can find signs characteristic of overheating, but in a weakened form.
According to G.K. Otryganyev, suffocated animals, as a rule, have hemorrhages in the allantois due to injury by the beak to still functioning blood vessels; There is a large blood clot near the beak.
Diagnosis of insufficient ventilation. Incubator air pollution has a negative effect on the development of embryos, but specific diagnostic signs of poor ventilation have not yet been found.
According to G.K. Otryganyev, the gas exchange of an egg can be disrupted due to insufficient ventilation, when the pores of the shell are clogged with dirt and the contents of neighboring broken eggs. If gas exchange is disrupted, growth and development are delayed. During the middle days of incubation, sudden suffocation (asphyxia) causes the same developmental abnormalities as acute overheating: overflow of the allantois vessels with blood, hyperemia, hemorrhages in the skin. A characteristic sign is the presence of blood in the amniotic fluid (hematoamnion). Insufficient gas exchange during the incubation period causes incorrect positions of the embryo in the egg, so shell pecking occurs at the sharp end of the egg.
Disorders associated with the position and rotation of eggs. The lack of turning of eggs leads to a large number of sticking and drying of shells and embryos to the shell. Unlike dryings, which appear at high temperatures and low humidity, in the absence of turning the eggs, all dead and dried embryos lie on one side (top).
If the eggs are not turned, there is an increase in embryo mortality during hatching.
An insufficient number of turns or an insufficient angle of rotation of the eggs causes, first of all, weak and incorrect development of the allantois, which does not close at the sharp end of the egg or closes very late. At the same time, there are many eggs in which the allantois grows with its edges above the white and, closing itself, leaves the white outside of itself at the sharp end of the egg. In this case, the young animals are hatched small and weak.
Disturbances associated with air speed. The speed of air movement does not directly affect developing embryos, but enhances or weakens the influence of other external factors - temperature, humidity.
In cabinet incubators, the speed of air movement ensures uniformity of the regime at all points.
The uneven development of embryos in all places of the incubator and the non-simultaneous start of hatching indirectly indicate the presence of zones, in particular temperature ones, due to insufficient air movement speed.
Air chamber, or scarecrow, is formed immediately after the egg leaves the oviduct.
The reason for its appearance is the difference between the chicken’s body temperature and the air temperature. The height of the chamber of a freshly laid egg is 0.10-0.35 mm. After 4-7 days of storage under normal conditions, it increases to 2-3 mm, and after a month it reaches 11-13 mm. As you noticed, the longer the egg is stored, the higher the height of the air chamber becomes. This parameter is used as an indicator of egg freshness. The height of the air chamber is measured using an ovoscope.
Ovoscope- (from Latin ovum, - “egg” and Greek skopein - “to examine, look”) - a device for candling eggs. It is used to determine their quality. An ovoscope is a plastic drum in which cells are made. There is a lamp inside the ovoscope. It illuminates the eggs from below, so that it becomes possible to see the contents of the egg, as well as the structure of the shell.
The battle- These are eggs with damaged shells. It is divided into eggs without signs of leakage and leakage.
Eggs without signs of leaking include a notch and a wrinkled side. Notches, as already mentioned, are microscopic cracks, almost indistinguishable without an ovoscope. Another way to detect notches is to tap eggs on eggs. A crushed side is a more serious and noticeable damage to the shell. In both cases, the shell film remains intact, so the contents of the egg do not leak out. If the integrity of the film is broken, a leak appears. Fighting is caused by careless handling of eggs during their collection, packaging, transportation, and sorting.
Pouring- This is mixing the yolk and white. It is divided into small and large. With a small pour, the yolk and white are only partially mixed. In this case, there is slight damage to the yolk shell, it has an irregular shape, and there may be dark inclusions or stripes in the white; the protein itself is liquid, with an admixture of yolk mass. A large pour is the complete mixing of yolk and white. It appears as a result of rupture of the vitelline membrane. The contents of the egg become yellowish.
Small spot- this is the formation of mold of various colors on the subshell films. It is formed as a result of mold getting under the shell. Eating eggs with a small spot is acceptable, but only while they are still fresh. Such eggs cannot be stored: a small stain develops into a large one, and this flaw already transfers the eggs to the category of technical defects.
Drying- drying of the yolk to the white. Occurs due to the liquefaction of the protein and the weakening of the hailstones - a kind of “anchors” that hold the yolk in the center of the egg. The yolk weighs less than the white, therefore, devoid of hailstones, it “floats” and dries to the protein shell.
Pumping- movement of the air chamber depending on the position of the egg. The reason for pumping is the rupture of the protein film in the area of the air chamber. Air gets under the film and the camera begins to “float”. Such eggs must either be eaten immediately or sent for processing: they cannot be stored.
Smelly, as the name suggests, are eggs with an off-odor. It appears, as a rule, as a result of storing eggs in the same room with odorous substances and materials. Eggs absorb any odors very quickly, which is why it is so important to store them only in clean, specially designed rooms.
Naturally, it is impossible to “ventilate” eggs, so smelly eggs cannot be stored.
Eggs with the following defects fall into the category of technical defects: paint, blood ring, cuff, large stain (mold cuff), mirages and eggs with a pungent, non-volatile odor.
Krasyuk- mixing white and yolk. Unlike pouring, it occurs due to prolonged or improper storage of eggs. Over time, they lose some of the water they contain. Its other part moves into the vitelline membrane. This becomes possible because as the egg ages, the yolk membrane becomes thinner and less elastic. The yolk enlarges and flattens. As a result, the shell breaks and the yolk mixes with the white. You can't eat these eggs.
Blood Ring- these are the remains of a dead embryo. This unpleasant defect occurs in a fertilized egg. If the embryo develops at elevated temperatures (21°C or more), blood vessels in the shape of a curved ring are visible on its surface when transilluminated. The embryo dies very soon, but such eggs cannot be eaten. They are sent for industrial processing.
Big spot, or cuff, which has already been mentioned in connection with a small spot, is the formation of large colonies of mold on the shell. Eggs with such a defect are destroyed.
Mirages- these are unfertilized eggs with embryos that died at later stages of development, as well as other incubation waste.
If you find an error, please highlight a piece of text and click Ctrl+Enter.
Articles on the topic
