How Do Chickens Fertilize Eggs: The Real Truth!

We eat eggs from the prehistoric age. Maybe the chicken eggs are the most eaten by humankind. But ever thought, how does an egg turn into a chicken? If you are thinking just like me, you may like my answer on how do chickens fertilize eggs.

There is a funny question that is knocking in our mind for many ages: egg first or chicken. But to satisfy our knowledge, we should actually understand the birth process of a chick from an egg. 

Also, if you find some eggs that already developed an embryo, what is the reason behind it? Let’s look at the points.

What are Fertile Eggs

fertilizer eggs

By fertile eggs, I mean the egg that can produce a chick. Sometimes, you start thinking the question is do chickens have to mate to lay eggs?’’ Your question’s answer is no because a hen can lay eggs without mating a rooster.This bird is very unlike other mammals that need the male and female to mate for reproduction.

If you break the shell of a fertile egg and look into its yolk, you will see a circular bull’s-eye shape. That is called blastoderm. With proper nourishment and perfect conditions for chicken egg development, you can get a new chick

If your question is can you eat fertilized eggs? we will give you the answer. Some people say that the fertilizer eggs contain better food value than unfertilized ones. But scientifically, there is no proof for that fact.

How Do Chicken Fertilize Eggs

how do chickens fertilize eggs

Chickens can fertilize eggs only if the hen and rooster mate before laying eggs. As I already said that the chicken could lay eggs without any mating with a rooster after a certain age. But those eggs will be unfertilized, meaning no matter what you do, they won’t turn into a chick.

But to fertilize an egg, the chickens must mate. It doesn’t mean having sex. Chickens can’t have sex like other mammals. Neither the hen has a vagina, nor does the rooster have any penis. Both of them have an opening at their bottom known as the cloaca. 

Rooster’s Participation:

When the hen is ready to lay eggs, the rooster invites it to mate. Usually, the rooster widens its wings and dances around the hen. The hen responds to the call by flattening itself on the ground. The hen raises its bottom, and the rooster vents its cloaca from the top and injects the sperm into the hen’s opening.

This is a rapid process. It generally takes just about 20 – 30 seconds. Then the sperm enters through the female cloaca and starts marching towards the ovary. In this process, it takes more than a week or even longer.  The active sperms start moving forward through the hen’s reproductive tract, known as the oviduct. 

Then the sperms move into the shell gland by swimming. On the way, they reach the narrowing isthmus tract of the oviduct. Then they cross the magnum and reach the infundibulum. There the sperms wait for the ovary to release eggs to fertilize.

Hen’s Participation:

Eggs start as yolk in a hen. The ovary releases yolk that goes to the infundibulum. There it gets fertilized by the reserved sperms. After chicken egg fertilizing, it started to form a zygote which is known as blastoderm. It remains in the infundibulum for 5 hours to complete the process.

While starting to move the eggs,the sperms come in the same path.When the yolk reaches into the magnum, it starts collecting egg white around. Egg white and yolk get a shell membrane in isthmus.It covers those from direct contact hard shell.Then the shell starts hardening on the shell gland.

The whole egg then rests on the uterus. Usually, a hen lays an egg in the morning, so; it keeps the egg holding inside. And this procedure continues for several days, and the hen lays an egg every two to three days.

As long as the sperms are active, each egg the hen lays will be fertilized. And with natural or artificial incubation, you can get a chick from those eggs. This is the process of how are chicken eggs fertilized?

Why Do Chickens Lay Unfertilized Eggs?

As I already mentioned that a hen doesn’t need to mate with a rooster for laying eggs. Also, I covered how a rooster fertilizes an egg. As we know, the hen can lay eggs after a certain age, so it will keep laying eggs naturally.

It needs a male chicken to participate in mating when giving birth to a new chick. Sperm from the rooster makes fertilized eggs that can become a chick. But if the hen won’t mate before laying, those eggs will be unfertilized.

As we know, reproduction in the animal kingdom occurs when both male and female gametes combine. That will turn into a zygote, and then the female will lay eggs or give birth to new offspring.

A hen can lay eggs without mating, so those eggs have a single chromosome from the female chicken and can’t form a zygote. This results in no new chicks ever can come out of those eggs.

Especially the poultry farms which sell eggs commercially don’t keep any rooster. Once an egg is fertilized, a chicken can be born from it if it meets certain conditions. An egg can produce chicken less than 99° Fahrenheit in 21 days. So, the egg production farms ensure that the eggs are unfertilized.

Though a small number of people believe that fertilized eggs are more tasty and delicious, most people will hate to see an unborn chick inside an egg. If the chicken doesn’t hatch babies from eggs, then it will lay unfertilized eggs.

How to tell the difference between fertilized and unfertilized eggs

fertilized egg vs unfertilized egg

While seeing naked eyes, you can’t find any difference between fertilized egg vs unfertilized egg. Both look the same under the shell.If you crack open an unfertilized and fertilized egg on the day those are laid, there is no difference.Then how do you know if a chicken egg is fertilized. Normally you can see eggs fertilized properly within three days.

When you crack a fertilized egg up, you will see a white ring over the yolk. That bull’s eye-looking ring is known as blastoderm. Blastoderm is the first stage of forming a zygote. If you see a blastoderm on egg yolk, then it is a fertilized egg.

When you are wondering, is there any scientific way to find out the difference between an unfertilized and fertilized egg? There are some ways. But first, let us get this straight there is almost no difference in chemical value between fertilized and unfertilized eggs. Both contain the same amount of elements before the embryo forms completely. 

But in a recent scientific test with 2-dimensional electrophoresis, researchers discovered there is some difference in ovalbumin. The fertilized egg white proteins show ten fold difference because of protein Y. It’s because the male gamete changes the chemical structure of the ovalbumin slightly. 

Understanding the fertilization function before actually getting real effects on the egg has been a challenge. For more chickens and unfertilized eggs for industrial purposes, researchers kept testing the eggs to differentiate between an unfertile and fertile egg.

Experts invented a Non-invasive Micro-test Technique (NMT) to distinguish features between a fertile and non-fertile egg. The test measures the respiratory rate function of the egg. And they found there is a massive difference in the oxygen exchange rate between fertile and non-fertile eggs. 

In this test, researchers look at the intensity and oxygen flux with the environment at room temperature. The study showed the fertilized egg exchange oxygen at high rates. The oxygen flux rate is more than 20 pmol/cm2. But the rate in an unfertilized egg is way lower. With this method, we can identify which one is unfertile and which is a fertilized chicken egg.  

How do farmers know if a chicken egg is fertilized?

farmers know if a chicken egg is fertilized

They understand the fertilized eggs using their experience and common sense. It is simple logic that the farmer will undoubtedly know which batch of eggs is fertile. Usually, the farmer decides which eggs he will sell to customers and will produce new chicks. 

A farmer keeps 1 or 2 roosters in a flock of chickens if the herd is in the high count, like 20 or more. But they keep the rooster in different cages to control the fertilization rate. But what if a rooster slides into the hen’s flocks and mates with them and fertilizes eggs. How does the farmer understand if the eggs are fertile or not?

For the test, they usually use an old and quite popular method.The method is known as “candling egg,” where you have to take the egg into a dark room and use a candle to look through the egg. Nowadays, people use lights instead of a candle. But take a mid-power light because if you try to look using a powerful light, you will see just bright light.

But while keeping the egg between the thumb and first finger, you will spot the embryo if you look through the egg. For that, you will have to take a fertilized egg that is at least three days old.This is the technique of the farmers which is using to check the fertility of the egg.

Frequently Asked Questions (FAQs)

How does a rooster fertilize an egg?

A rooster fertilizes an egg by sharing sperm with the hen. The number of eggs those  a hen can lay is just fixed upon its birth .When it comes to a mature age, it starts laying eggs without mating. But a rooster mates with a hen called “cloaca kiss,” and passes sperm into the hen’s reproductive system. The sperms combine with the yolk and that ensures by hatching the egg can turn into a chicken.

How long does it take a rooster to fertilize an egg?

It usually takes 25 hours for the sperms to reach the infundibulum. And those sperm start fertilizing eggs in 3 – 7 days.

How do you tell if an egg is fertilized after cracking?

When I break an eggshell and keep it in a bowl, I look at the egg yolk. If I find any bullseye-like ring there, I can justify that egg as a fertilized one. But if that doesn’t happen, it is impossible to tell if the egg is fertilized without any experiment.

Can you eat fertilized eggs?

The short answer is yes. Yet if you take a fertilized egg that developed an embryo, I won’t recommend eating that. But as soon as you keep the eggs in the fridge, the embryo development stops.

So the Point is…

Fertilized eggs vs. unfertilized eggs debate have been there for a long time. If you would like to eat any fertilized eggs, you can get them from any grocery shop. And if you ask where to buy fertilized eggs, you can find some shops selling fertilized eggs in unique corners.

We hope this article satisfied your query about how do chickens fertilize eggs. If you believe that fertilized eggs contain more health benefits, get some fertilized eggs for sale. A lot of stores sell them on request as well.

Joy Dolcini

Hello! I am Joy Dolcini. I have been working in poultry farming for a long time. Being an optimistic and successful poultry farmer. From my passion and experience, I tried to share knowledge of farming by writing. The sole intention of my writing is to help farmers to enhance farming skills and learn essential techniques. Read More

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