Reasons for porous eggs?

[11ChickenGirl11]

The first time I tried setting eggs under a broody (this spring), none of the eggs hatched or even developed. I remember when my mother and I were candeling eggs to check for fertility (I now know that is not possible without breaking them open), some of the eggs were very porous and some other eggs broke under the broody.

What are the main reasons for porous eggs to occur?

 

[Pork Pie]

This link may help

http://www.backyardchickens.com/a/common-egg-quality-problems

 

[11ChickenGirl11]

Thank you! That article was just what I was looking for!