Incubation & Hatching
When incubating eggs, there are five key factors to bear in mind:
- Temperature – With the egg at the correct temperature (for most species this is 37.5°C), the biological process of incubation will commence and the embryo will begin to grow. The temperature must be sustained throughout the incubation period.
- Egg turning and positioning – As the egg is turned, the embryo will pass through the egg white, allowing it to gain fresh nutrients. As the embryo grows, correct positioning of the egg ensures that the embryo forms in the correct position for hatching.
- Humidity – The shell of an egg is porous, meaning that water can pass through it. Over the egg incubation period, water passes from the egg to the air outside. Correct humidity ensures that the right amount of water is lost over time. It is important to remember that humidity will vary, and this is not a big problem; it is the average humidity that matters more.
- Fresh Air – It is important to note that during incubation the egg breaths; it takes in oxygen from the surrounding air and gives out carbon dioxide. A fresh air supply is vital to egg incubation and hatching eggs.
- Clean Environment – During incubation, eggs are susceptible to infection. The warm, egg incubator is a perfect breeding ground for bacteria. Eggs should be clean and disinfected before egg incubation begins.
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What species are you incubating?
There are two types of bird species and, although the basic principles of egg incubation remain the same, it is important to understand the differences between the two. Hatching a chicken is very different to hatching a parrot, or hatching a bird of prey.
Precocial Birds – These are birds such as poultry and waterfowl, which are capable of moving around after hatching.
Altricial Birds – These are birds such as parrots or birds of prey, which are incapable of moving around after hatching, and require more, intensive care brooding.
So what are the five main differences between the two types of bird?
Hatch with their eyes open
Hatch with their eyes shut
Hatch covered with down
Hatch with little and sometimes no down
Leave the nest within the first two days of hatching
Incapable of departing the nest
Will forage for food within hours of hatching
Fed by parents
Eggs are turned less frequently
Eggs are turned more frequently
There are 6 main parts to a fertile egg: the shell, the shell membrane, the albumen (egg white), the yolk (yellow), the chalazae (supporting tissue) and germinal disc (the fertile area visible as a white spot on the egg yolk).
Shells can often vary in shape from species to species, however, usually one end is round and the other end is more pointed. This means that if an egg happens to roll, due to wind or other elements, it never rolls too far from the nest; a clever evolutionary feat of Mother Nature.
The shell of an egg is porous; meaning liquids and gasses can pass through it. The porous shell of the egg allows an easy interchange of oxygen, moisture and carbon dioxide.
Another fascinating feature of the shell is that it is thinker and denser on the outside than on the inside. This allows the chick to break out of the egg much easier than a predator could break in.
The yolk is, in essence, the food store of the egg and is made up of water, proteins, fats, vitamins and minerals. This food store is not primarily used in the incubation of the egg as many people think, but is the main source of food for the newborn chick within the first few days of hatching.
Day old chicks do not require feeding straight away after hatching, as they have an adequate amount of food available from the egg.
These are spirals of supporting tissue within the egg white, or albumen. The Chalazae are connected at both ends of the egg, holding the yolk in its central position.
The spiral threads are coiled in opposite directions, meaning it is vital not to turn the eggs continually in one direction; this will result in one of the threads becoming too tight, whilst the other becomes too slack. Eventually one will snap and the yolk will not be able to keep its position inside the egg.
During egg incubation, eggs should be turned through roughly 45 degrees in both directions; the chalazae will therefore remain intact.
There are two membranes inside the egg. The outer membrane lines the inside of the shell; whilst the inner membrane is only loosely appended, separated from the outer membrane at the broad end of the egg by the air sack (also known as the air cell). During incubation, the space between the two membranes increases as the egg looses moisture; this increases the air supply available to chick in the final few days before hatching.
Also known as the “white” of the egg, the albumen is composed of protein, water, vitamins and minerals. The albumen’s primary purpose is to protect the yolk from damage. However it is also a food store for the growing embryo during the egg’s incubation.
The albumen is composed of three different layers, each performing different function. The thin, watery outer layer has contact with the inner and outer membrane and allows the diffusion of gasses and moisture with the outside world.
The thick and viscous, jelly-like, inner layer provides a cushion for the delicate yolk, absorbing any shocks that the egg may suffer. The inner-most layer of the egg white is also thin and watery, acting as a lubricant for the egg yolk, allowing it to rotate freely in the middle of the egg. This ensures the yolk and germinal disc have ready contact with fresh supplies of food and oxygen.
The germinal disc is the fertile part of the hatching egg; the part where the male and female cell unite. A broody hen, or correctly calibrated egg incubator, the cells will begin to divide. Incubation and embryonic development have begun.
Nutrition of the egg
The egg is made up of many nutrients, vitamins and minerals that come from the parent. Hens need a variety of nutrients at least two weeks prior to laying.
The most important nutrients are:
- Vitamin A – Obtained from green feeds and vegetables; a lack of Vitamin A causes poor hatch rates, weak chicks and poor resistance to disease.
- Vitamin D – Obtained from sunlight; a lack of Vitamin D causes weak bones and misshapen eggs.
- Vitamin E – Obtained from seed germs (i.e. Wheat); a lack of Vitamin E can result in weak chicks and circulatory failure.
- Vitamin K – Found in most green feeds; a lack of Vitamin K can cause haemorrhaging.
The hen’s ovaries are positioned in the back of her abdominal cavity. There are several yolks inside the ovaries, at different stages of development. As they grow larger over time, the yolks move to the top of the oviduct passage, which eventually lead to the uterus.
In the upper-oviduct, the male sperm fuses with the female cell in the yolk. The fertilised yolk then travels down the oviduct (or egg canal) where it acquires coatings of albumen (egg white) followed by the shell membranes, the shell gland produces the shell and the completed egg travels to the uterus.
By the time the egg reaches the uterus, the hard shell has completely formed. It then moves to the vagina to be laid. This whole process usually takes 24 hours, however can sometimes take 36 hours.
Egg Collection, Storage and Handling
It is best practice to collect the eggs before 9am and to check back at midday in case the hen has laid any more. However, the more frequently eggs can be collected; the less chance there is of them becoming soiled or dirty. Eggs that are left in the nest for more than 24 hours tend to result in poor hatch rates.
Eggs are usually collected in a basket or rubber bucket. It is very important that eggs are handled carefully to avoid them getting jarred or cracked. Many people add an extra layer of kitchen roll or wood shavings into their basket for increased security.
It is also important to wash ones hands before collecting the eggs. Your hands are the perfect breeding ground for bacteria and this can easily be spread to the eggs. If your hands are sweaty or greasy, this can pass onto the eggs; blocking their pores and preventing respiration and moisture loss – all of which can affect the chances of a hatch. Before collecting the eggs, wash your hands carefully with anti-bacterial soap or incubation disinfectant. Rubber gloves can also prevent the spread of germs and bacteria.
Egg storage is an optional step before egg incubation. Many breeders of hatching eggs prefer to build up a “batch” of fertile eggs before commencing egg incubation. The duration for which to store your eggs is completely up to you. However, it is not recommended to keep your eggs any longer than 10 days before incubation.
During storage, it is very important that you ensure the quality of your eggs. Cracked, misshapen or heavily soiled eggs should be discarded to avoid contamination. Some slightly dirty or soiled eggs can be washed with incubation disinfectant. When washing eggs, make sure that the water or solution you use to clean the eggs is significantly warmer than the egg temperature; this will cause any bacteria to be drawn away from the pores.
Washing your eggs is highly recommended. However it is important to note that this process will remove the egg’s natural, thin outer coating. This will leave the egg vulnerable to future infection so it is vital a high level of cleanliness is maintained throughout the egg incubation period.
Storage Temperature & Humidity
When storing eggs it is recommended to keep them at a room temperature of between 15°C and 18°C. Cool, draft free locations are ideal places to store your eggs. Before incubation, eggs should be brought steadily up to room temperature. This avoids drastic temperature changes and “thermal shock” to the egg.
As for humidity, lower is better, but not essential. Some breeders of hatching eggs recommend a humidity level of between 45% and 55% RH; this is ideal, however, unless you plan to incubate eggs on a large scale, you are not likely to witness any difference.
Egg Turning During Storage
During storage, eggs should be turned a minimum of once a day; two or three times per day is much better.
When turning eggs, try to make sure each egg is turned 45 degrees each way, totalling 90° over the course of a day. Turning the egg during storage ensures the eggs outer membrane does not stick to the shell.
The method you use to turn your eggs is up to you. Some people prefer to turn their eggs manually by hand, whereas some prefer to place their eggs pointy side down in an egg box at an angle, and change the angle of the egg box two or three times a day. However a growing number of people use their egg incubators to turn their eggs before incubation. This can be achieved simply by using removable automatic egg trays, or by placing the eggs in the bottom of a rocking incubator with just the rocking motor on.
Egg Handling Tips
Eggs should always be handled with the upmost care. Severe bumps may rupture the egg’s internal membrane, even if the egg shell appears undamaged.
Care must still be taken when handling eggs in the incubation stage. A severe bump can rupture blood vessels; causing the chick to bleed to death.
If eggs have endured a lot of handling, perhaps from being sent in the post, it is important to set them pointy side down for at least 24 hours before incubation. This will allow the contents of the egg to settle.
Choosing the right Egg Incubator
Still air or fan-assisted?
Egg incubators can be still air or fan assisted (also known as "forced air"). In still air egg incubators, air circulates by convection; as the warm air rises in the incubator, it displaces colder air. This cycle creates natural air circulation. However, in still air egg incubators, it can be much harder to establish the correct incubation and hatching temperature. This is due to the fact that some parts of a still air incubator are cooler than others. If the incubating eggs are on more than one level, a still air egg incubator can produce poorer hatch rates.
The alternative to still air egg incubators is fan-assisted, or forced-air, egg incubators; in which the air is forced over the eggs and throughout the incubator by means of a fan. Fan-assisted egg incubators are becoming increasingly popular due to their increased chances of success. Larger, cabinet incubators need to be fan-assisted due to the volume of warm air needed inside the egg chamber.
There are three main types of egg incubator available on the market;
Manual Egg Incubators are simply a heated box controlled with a thermostat. Eggs need to be turned individually by hand. For people looking for cheap egg incubators, manual egg incubators are often a popular choice; homemade egg incubators are often manual.
Semi-automatic egg incubators do not require eggs to be individually turned; instead, the whole batch of hatching eggs is turned at the same time by an external control or lever. The turning method on semi-automatic egg incubators differs from model to model.
Full automatic incubators will automatically turn the eggs throughout the day. The way in which the eggs are turned varies from model to model, however the most popular methods are via a moving floor; or by sitting the egg incubator in a turning cradle, the machine is then electronically tilted from side to side.
In modern incubators, the heating element is almost always powered electrically through a standard rated electricity supply. The incubator’s thermostat plays a key role in ensuring the correct incubation temperature is present throughout the incubation period. Modern, electronic thermostats are much more accurate than their traditional counterparts; such as the “wafer thermostat”. The main benefit of digital thermostats is their acute sensitivity to temperature fluctuations; they are able to respond instantly to environmental changes, turning heat on or off as necessary.
Many incubators control humidity using a simple water reservoir in the base of the egg chamber; such reservoirs are topped up manually as many times as is advised by the manufacturer. Other machines use a humidity block or pad that need to be kept moist throughout the incubation period. When topping up an incubator’s water levels, it is important that the water is not too cold; this can result in a dramatic temperature reduction within the egg chamber. Similarly, it is just as important that the water is not too hot. Try where possible to ensure that the water is around 37.5°C.
Of course, some modern incubators are fitted with highly accurate digital humidity pumps. These take human guesswork away from incubation, leading to much more accurate humidity levels. This level of accuracy, although desirable, is not vital to successful egg incubation.
The Egg Incubation Process
Stage 1 (Fertilisation)
The yolk is dropped from the ovary and fertilised by the male sperm. The fertilised yolk then travels down the egg canal and receives several coatings of albumen (egg white). The shell is then developed in the hen’s shell gland. This process takes approximately 20 hours; after which, the egg is laid.
Stage 2 (Days 1 and 2)
The egg is hatched and gradually cools. At this stage, embryonic growth slows and often stops. Many birds will develop a “clutch” of eggs that they wish to incubate. The clutch size depends on a variance of factors including hereditary traits and environmental factors.
For artificial incubation, the breeder can actively choose the clutch size they wish to incubate. He or she may choose to store the eggs at room temperature (15-18°C) for up to 10 days in order to gather the required amount of eggs.
On the first day of incubation, embryonic growth begins again and the cells begin to divide and multiply rapidly. By the end of day one, the head, eyes, nervous system and circulatory system have begun to form. The heart is formed on day two and is functioning within 48 hours of incubation.
Stage 3 (Days 3 and 4)
On day three, the heart develops from its simple form to become a fully functioning, beating heart. Additional membranes are formed in this time. This creates the amniotic sack which the embryo will float in for the duration of incubation.
Within the amniotic sack; amniotic fluid, combined with correct egg turning, ensure the embryo orients itself correctly during hatching.
Although the heart is still positioned outside the body, by the end of day four, the legs and wing buds have began to form.
Stage 4 (Days 5 – 10)
By the end of day six, the legs and wings are nearly complete. Feathers begin to appear at day eight, and by the end of day nine the embryo is beginning to look like a chick - the chicks heart is now in place within the body. By day ten, the bones are beginning to form.
Stage 5 (Days 11 – 21)
By day thirteen, the chick’s down feathers are fully formed and present on most of the chick’s body. The legs and wings are also complete with bones and muscle tissue. By day sixteen, the beak, leg scales and claws are very nearly complete. The remaining yolk then becomes a food source for the developing chick; this is used up by day nineteen.
At day nineteen, the chick is beginning to struggle to get enough oxygen to its blood; carbon dioxide levels in the chick’s blood begin to rise dramatically. A rise in the CO² level within the chick’s blood causes the chick’s neck to twitch; its beak is forced through the membrane sack into the air sack at the blunt end of the egg.
The beak then opens for the first time and the lungs inflate; fresh oxygenated blood is then circulated around the body. At this point in the incubation period, the chick is under significant stress; many chicks die at this stage of incubation because they are too weak or undernourished to deal with the stress they are under.
Stage 6 – Pipping (Day 20)
A day or so before hatching, the chick begins to “chirp”. Chirping is the sound made by the chick in an effort to communicate with its mother. The mother then naturally chirps back encouragement. In artificial incubation, some breeders enjoy chirping back to the chick to encourage it to hatch.
The chick continues to breathe from the air sack but soon begins to run out of air. This again begins to cause the chick’s neck to twitch involuntarily. At this stage the chick’s beak begins to penetrate the outer shell; this is known as “pipping”. The chick’s legs begin to move and twitch which causes the chick to move around inside the egg and the hole gets bigger. After an initial hole has been made, it is likely that the chick will pause (sometimes for up to 24 hours) to regain some strength and energy.
By the time pipping begins, egg turning shouldhave ceased. This is very important as on day twenty, the chick gets itself into its ideal hatching position inside the egg; egg turning at this point would completely disorientate the chick and may result in injury or death.
Stage 7 – Hatching (Day 21)
On day 21, the chick will make a determined effort to chip off the top at the rounded end of the egg. The chick takes its first gasp of air as the top of the egg is released. It will usually rest for a while here, but will then go on to prise off the bottom half of the shell.
The hatching process takes time and the chick is visibly exhausted after its ordeal. When the chick hatches it is likely to be wet, but all the yolk should be absorbed into the chick’s stomach. If there are any large pieces of yolk attached to the chick’s bottom that were not absorbed into its stomach, the chick has a hernia and unfortunately will not survive.
The newly hatched chicks will stagger clumsily around the incubator or nest stopping for frequent rests. Do not worry; it is often the case that some chicks appear very tired and unwell after they have first hatch. But after a short rest, chicks are very likely to spring back to life at the first sign of a stimulus.
Never turn off the incubator too early. Some eggs will naturally hatch later than others. Leave the un-hatched eggs in the incubator for at least another 24 hours after the expected hatch day; you never know, they may just surprise you. Remember to resist the temptation to keep opening the incubator. Chicks are very sensitive to the cold and, by opening the incubator lid, valuable heat energy is lost. Chicks will happily remain in the incubator for 48 hours after hatching. They will not need any additional food and water during this time, as they will have enough food remaining in their bodies from their time inside the egg.
After 48 hours in the incubator after hatch day, the chicks should then be moved into a brooder. Brooding equipment can be found here on our website!
Optimum Conditions for Incubation and Hatching
|Bird Species||Temperature °C||Humidity RH%||Pipping||Hatching|
|* Varies depending on species|
Note: The above information is only to be used as a guide to incubation and hatching and will not guarantee a successful hatch. Always refer to the manufacturer’s instructions.