Strange eggs

[Gr8bawana]

Have any of you guys that have chicken ever seen these little bumps on the outside of the shell?
We have 4 chickens and I think only one of them is laying these eggs. They look completely normal inside and they taste like any other egg.
Just curious as to what might be causing this.

 

[TN2shot07]

I was always told that’s excess calcium in their diet

 

[Gr8bawana]

It could be true but I would think since all the chickens are eating the same thing more than one would lay eggs like this.

 

[jryoung]

Are they laying less often? More time in the vent could be leading to more calcium deposits.