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Brown shells carry protoporphyrin pigment, and blue shells carry biliverdin. The figure is taken from Encyclopaedia Britannica, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.

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Eggshell colour depends on the hen, not the yolk

Brown shells carry protoporphyrin pigment, and blue shells carry biliverdin

Shell colour is decided by the breed of hen and the pigments deposited in the shell gland during the final hours of laying. Brown eggs get their colour from protoporphyrin IX, while blue and green eggs come from biliverdin, a breakdown product of haem. The yolk colour is a separate matter, set by the hen's diet and its carotenoid content.

Where this comes from

Encyclopaedia Britannica

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Tags: eggs, pigment, poultry

Eggshell colour depends on the hen, not the yolk: the short answers

Where does this come from, and can I check it?: Brown shells carry protoporphyrin pigment, and blue shells carry biliverdin. The figure is taken from Encyclopaedia Britannica, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
Is this really a food fact?: Yes. It sits on the Food shelf, one of 1,090 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
What else can I read about it?: The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.