How to Determine If a Chicken Egg is Fertile and Developing

If you’re wondering How to Tell if a Chicken Egg is Fertile and Developing, this post might help! There are a few tricks you can use to help!

Requirements for Chicks to Develop

As a chicken owner, you might wonder if your eggs have a fetus inside them. The requirements for chicks developing inside an egg are as follows:

A rooster mounting all the hens and fertilizing her eggs
A broody hen who sits on the eggs for them to develop
Warm temperatures (which makes the hens go broody)

If you checked off all of these requirements, you might have an egg that contains a developing fetus. However, if the rooster fertilizes an egg, it still needs the proper conditions to develop into a chick.

You might be safe by cracking open a fertilized egg and not seeing any fetus. But if you have a hen sitting on the egg for more than a couple of days, and you take that egg, there is a chance you might see a little embryo if it gets cracked open.

Last summer, I remember not being able to find where my layer hens were laying their eggs until it was too late. There was a pile of eggs that had been sitting out in the sun all day for several days. The heat made some of them develop and made others rotten. It was the worst discovery, very sad and stinky! You can watch that video here.

There are some ways you can determine if a chicken egg is fertile AND developing. The best practice I found is a flashlight to light up the inside of the egg. As you can see in the image above, the tiny embryo is in the center. The veins are also an indicator of life inside. Neat, huh!?

All you need to do is place a flashlight, even the one on your phone under the egg in a dark room. You can use your fingers to close up the light shining around the egg. You only want your egg to be lit.

I learned this in my Agriculture program when I was in school. It has been very helpful in determining if an egg contains a developing fetus.

How to Stop Hens from Being Broody

I wrote a detailed article on how to stop hens from being broody and hatching more eggs. If you are like me, with enough chickens, and don’t want more roosters especially, then you can read the article here.

It is the saddest thing cracking open an egg with a living being inside. I try not to let this happen, but chickens are outnumbering me and keep multiplying without me knowing. So, I have to keep track of the eggs 🥚 at all times.

How to Determine If a Chicken Egg is Fertile

When you crack an egg open after performing the light test to see if there is a developed chick, there is still another test to determine if the egg is fertilized.

The word Derm means skin. “A true fertile egg contains a well-developed germinal disc (blastoderm), which indicates that the oocyte, or zygote, was fertilized and an embryo developed during egg formation.” ¹

The Difference in Fertilized Eggs?

Fertilized eggs can only happen when there is a rooster present. The rooster will do its job thereby fertilizing the hen’s egg inside her. There is no nutritional or taste difference between fertilized eggs and unfertilized eggs.

The only difference is one can become a chick, while the other one does not.