What is causing these dark spots on the shell?

[dmvelez]

We have a hen who FAITHFULLY lays a big brown egg EVERY DAY since she started laying about 7 months ago. Recently, a lot of them have a large dark spot on the large end, only there. A couple even came with the dark spot and lots of white stuff in the same area. This is NOT normal for her, but I'm worried I've seen so many like this recently. Can anyone tell me what is causing this? Is it something to do with her health or nutrition?

 

[sumi]

See #7 here: https://www.backyardchickens.com/a/common-egg-quality-problems

 

[aart]

Could be a pigmentation thing...the whitish part could be excessive bloom.
Have you washed these eggs?
Does the dark spot have a different shell thickness?
Do they look ok inside...any difference in whites or yolk?

 

[Dolores_and_Audrey]

I have a hen laying the exact same looking eggs as these. The darker spots are rougher/thicker almost? Combined with white "calcium" coating too and the shells are rougher than usual. Eggs are normal inside.

I must add, she is currently (I suspect it's this hen) unwell exhibiting some raspy breathing -intermittently- and seems happy otherwise. But the raspy breathing has us thinking it might be gapeworm - occasional gasping but the breathing sound is the more prominent of the symptoms. Have already had another chook who was suffocating with the same breathing and now this one has the same symptoms. 3 different vets thought it was bacterial upper respiratory infection (+ possibly viral without tests only swab). Treated with 3 different antibiotics and still the first chook didn't make it I know now that antibiotics are so detrimental to a chook's immune system and have been feeding lots of pre- and probiotic foods (lentils, flax meal, unsweetened coconut yoghurt) + now tried garlic + DE in addition for suspected worms. Vets seem useless and although rare, the symptoms fit for gapeworm, so we're getting some deworming pellets and see if that helps.

Does yours have any of these symptoms?

 

[Dolores_and_Audrey]

Just reporting back - After the worming pellets the symptoms have completely subsided! I believe it was gapeworm. However, I still can't understand the reason for the markings on the eggs, I feel they are a bit different to the link Sumi copied. She has since stopped laying as she is now molting.