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How Do Chicken Eggs Develop?

Last Updated: 22.04.24


If you’re thinking about starting a business in the chicken meat or egg industry, our recent post will guide you through the basics of a chicken farm and will even give you some good chicken feeder ideas to help keep your birds happy and healthy at all times. We’ve also decided to talk more about the entire chicken developing process and, more specifically, how eggs hatch. Here is what we think it’s important for you to know.


Do hens need roosters to lay eggs?

One of the most common questions people ask regarding chickens is regarding the egg-laying process. The short answer is no, chicks don’t need a rooster to lay eggs. Depending on the size and breed, most chicks start laying eggs at around the age of five-seven months and will continue to do so throughout their lives.

The process is a little bit complicated, but we will get to it later on. What you need to know is that, while chickens don’t need the rooster’s help to lay eggs, the eggs won’t be fertilized and hatch without the help of a male. In other words, if you’re planning on farming chickens solely for their eggs, you won’t have to also invest in buying roosters.

Can supermarket-bought eggs hatch?

Another common question regarding eggs and the hatching process, in general, is if the eggs that you generally buy from the supermarket can potentially hatch and reveal live chickens. Again, if you’re looking for the simple answer, it is most likely no.

As we’ve previously mentioned, eggs need to be fertilized by a male chicken or a rooster in order for them hatch. Most chicken farms only allow the birds to lay eggs, without considering the fertilization part. Basically said, unless you plan on breeding chickens for their meat, roosters aren’t needed in the egg industry.

Even if, by accident, you would end up with a fertilized egg on the counters of a supermarket, hatching would still be close to impossible as the eggs need to be stored in cool places like refrigerators in order not to rot. It takes a solid three weeks for a single egg to hatch if it is kept at specific temperatures of around 100 degrees Fahrenheit, so you shouldn’t worry about getting a surprise omelet out of your supermarket eggs.


How do chicken eggs develop?

As we’ve previously mentioned, the process of turning a simple egg into a potential new chick is complicated and takes time. Nevertheless, if you’re willing to learn more about it, here are the most important phases.


The yolk release

Although hens are born with two ovaries, only one of them is functional and capable of producing eggs. Inside the ovary of the hen, there are thousands of potential eggs or ova. At any rate, when your bird reaches the sexual maturity to start laying eggs, a few ova start maturing into what is later recognized as an egg yolk.

Each of these yolks or ova begins developing in its own follicle and, when it is ready to move to the next phase, it breaks free from the follicle and travels down the reproductive tract or the oviduct. This entire process lasts around 15 minutes and sets the ground for the next phase, where the white forms.


The white formation

This phase lasts for several hours and begins when the yolk finally leaves the ovary and travels into the oviduct. This is also known as the place where the egg is fertilized by the rooster in order to potentially develop into a living being. Out of the oviduct, the egg continues its formation, whether or not it is fertilized.

In this phase, the yolk is known as a blastoderm and begins its journey down the oviduct. It is also the phase where most of the egg white (albumen) starts forming around the egg yolk. Both the yolk and the albumen are held together by a thin shell membrane.

At this point, the egg begins taking its known form, although it still misses the outer hard shell.

The eggshell

The third phase of the egg development process lasts around a day and refers to the formation of the actual eggshell. Chickens have a special shell gland in their uterus that allows this thick shell surrounding the yolk and the egg white to form. It takes about 20-21 hours for the shell to form and another couple of hours to gain pigment. Depending on the exact time, the exterior of the egg can look white, brown or even pale shades of blue or green.

The outermost eggshell layer is also called the cuticle or the bloom and has a protective role that will prevent bacteria and outer organisms attacking the “fruit” inside.


The nesting part

Once the egg is fully formed, it is released through a tube called cloaca, which is also used for excretion. However, the tissue of the uterus actually extends with the egg, protecting it and keeping it clean until it is fully released by the chick.

After the egg is laid, it takes about half an hour for the entire process to start again, which is why farmers are able to collect eggs from their hens every day.

If the egg has been previously fertilized by a rooster, chickens switch from their “laying egg” mode to the “hatching” mode immediately and begin covering the eggs with their body to keep them warm. The entire process lasts around three weeks during which the hen rarely leaves the nesting box and doesn’t allow anyone near her eggs.

It is only after those three weeks that we can talk about an egg being cracked to reveal a living creature inside. However, most of the hens don’t get into the hatching mode simply because the eggs are taken from them soon after they were laid.




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