How to tell if eggs are fetilized

[PeekinPekin]

Hi! I have a question.... I have a few clear eggs in my incubator. I am planning on giving them a little more time but when I do give up on them if I crack them open should they have blood spots if they were fertilized? In other words, do all fertilized eggs have the red spot or only the ones that begin developing? Thank you!

 

[Ridgerunner]

There are different things that can stop an egg from developing, even if it was fertilized. The embryo is alive and developing from the time it is fertilized until it hatches or dies. Since the inside of the hen’s body is about incubation temperature the egg develops the entire time it is in her body, until it is laid. That’s why you can see the bull’s eye if you crack a fertile egg. You won’t see a red spot because it takes longer than the egg is in her body to get to that stage. Here is a thread that talks about the bull’s eye.

Fertile Egg Photos
https://www.backyardchickens.com/t/16008/how-to-tell-a-fertile-vs-infertile-egg-pictures

If that embryo dies before incubation starts then there will be no development. There will be no red spot.

When the egg is stored at less than incubation temperature, development of that embryo really slows. It slows enough below certain temperatures that you won’t see any significant difference in development in a two week old egg versus one a day old. That’s why you don’t want to store eggs at too high a temperature. It can develop to the point it dies from lack of warmth or it may hatch a couple of days early. If that embryo ever totally stops developing, it dies. That’s why too cold of storage can be bad.

When you open those eggs you should be looking for the bull’s eye to see if they were initially fertile more than the red spot, but if development is there the red spot is a lot easier to see. When I open eggs that have been incubated for a while, the whites are so runny and the membrane around the yolk so weak the yolk practically always breaks anyway so you can’t really look for the bull’s eye on them.

The best way to see if you are getting fertile eggs is to look for the bull’s eye before you set any eggs. If you are seeing the bull’s eye in most of the eggs you open, most of the eggs you don’t open should have it too.

 

[PeekinPekin]

Thank you so much! That was very helpful!