How are chicken eggs fertilized?
I’ve lost count of the number of sets of chicks we have at our place.
I’ve actually found new homes for all our roosters now because it becomes a bit overwhelming – there were new sets of chicks hatching all over the place!
Before researching and writing this article, I wasn’t clear on how eggs are fertilized either, so it’s been fascinating learning all about it. As I’m sure you can guess, chicken reproduction takes two; a hen and a rooster, and it isn’t all that complicated…
How Are Chicken Eggs Fertilized?
So how does chicken egg fertilizing happen?
This is how it goes down:
- The rooster will do a dance around chicken
- The chicken squats down for mating
- The rooster hops on and mates with chicken
- Sperm fertilizes the egg yoke before the ‘egg white’ or the shell has developed
- The fertile egg is sat on for 21 days before hatching
However, even after reading that, it’s hard to picture it without an illustration.
This is the chicken reproduction system in the following diagram.
An egg is fertilized by the sperm in the Infundibulum, not long after the yolk has been released from the ovary.
Once an egg is released, this is the process it undergoes:
- The yolk is released and begins its journey down the ova duct
- The yolk travels down the Infundibulum for 15 mins and is fertilized (if at all)
- Next, over 3 hours in the magnum it is covered by albumen (egg white) and held in place
- In the Isthmus, the shell membranes are deposited
- In the shell glade, over 20 hours, the shell is formed and shaped
- Finally, the egg is contracted out of the chicken
It is quite extraordinary and something to marvel at – like most things in the world when it comes down to it!
The best way to get a complete scientific illustration of all this is to watch the following video.
I think that really helps to explain how a hen’s eggs are made.
Other interesting points from this mini-documentary on egg development:
- Chicken repro tract made up of ovary and ova duct
- The yoke grows in the ovary and the rest of the egg forms as the yoke passes through the ova duct
- Chickens only have one ovary
- Eggs are 1/3 water, 1/3 protein, 1/3 fat
- Yoke is released once it is 25mm wide
- Once released it takes 24 hours to go through the ova duct and become a complete egg
- Fertilization takes place once the yoke has left the ovary
There is so much more incredible information in the video above – you’ve got to watch it!
One of the final points is about how the chicken’s body temperature is around 106°F.
The temperature that an egg is laid into is about 20 – 40°F less than this – around 66 – 86°F (get a good chicken coop heater if it’s any colder than this).
This drop in temperature results in the little air pocket we find in our boiled eggs.
When a chick is ready to hatch in a fertilized egg, it breaks that little air pocket and takes its first breath before breaking out.
So you see, chicken egg fertilization isn’t as magical and mysterious as it seems at first, though it is still truly amazing.
It takes a boy and a girl chicken, and the fertilization process simply takes place before any egg white or shell is formed.
For a slightly less scientific version of the process, check out this video from Becky.
Chicken egg fertilization facts:
- The yolk is what becomes the chick
- The white is what the chick eats
- If you’ve even noticed the air bubble in boiled eggs, this is how a chick gets its first breath before hatching
- The chicken will store sperm inside her and use it to fertilize eggs over time
And that’s how chicken eggs become fertilized. It’s also totally OK to eat fertilized eggs, as long as they haven’t started incubation.
Chick Egg Fertilization FAQs
How soon before being laid is an egg fertilized?
Eggs are fertilized 24 hours before they are laid.
It takes 24 hours for an egg to leave the ovary and be laid out the vent.
How do you know if a chicken egg is fertilized?
Hold a light up behind an egg and look through it – use a flashlight, candle, or lighter.
If you are not able to see through it well, and you have a rooster, the egg is likely fertilized.
Can hens lay fertile eggs without a rooster?
No, eggs cannot be fertile without a rooster.
Without sperm, there will be no fertilization of the egg.
Can you eat an egg right after it’s laid?
Yes, there’s nothing wrong with eating a freshly laid egg.
If boiling them, it’s best to use slightly older eggs as they are easier to peel.
How long can fertilized eggs survive without heat?
A fertilized egg remains viable for up to 10 days after being laid before they need to be sat on or placed in an incubator.
Whenever one of our chickens goes clucky, we like to ask around for some different breeds of chicken eggs to put under them. It’s nice to try out different types: black chicken breeds like Ancona or Australorp, or bantam breeds like silkie or pekins, for example.
We’ve pushed fertilized eggs out this long before getting them under a chook and have had no issues with their hatching.
How long do fertile eggs take to hatch?
It takes 21 days for an egg to hatch once it has been consistently raised to 99 degrees (under a chicken or in an incubator).
Are Chicken Eggs Fertilized?
As a rule, eggs from the store are not fertilized.
If you are getting eggs from a local farmer, hobby farm, or neighbor, and they have a rooster, then they probably are.
There’s nothing wrong with eating fertilized eggs, as long as they haven’t been raised to temperature for a few days nothing will have developed.
Let us know if you have any more questions in the comment section below!
You might also like to find out the answer to ‘how long does a chicken live?‘.