What Makes Blue Eggs Blue?

February 6, 2018


All Eggs Start Out White

All chicken eggs start out with white shells which are made primarily of calcium carbonate. The calcium in chicken layer feed supplemented by crushed eggshell or oyster shell and the calcium in other foods your flock consumes creates the shells.  


No matter what breed the chicken or what color an egg ultimately ends up being, all eggshells are white as begin their journey down the oviduct.

Some of the white egg laying breeds include Andalusians, Catalanas, Lakenvelders and Leghorns among others. These breeds don’t possess any pigment genes, so they lay white eggs.

Brown Eggs are the Most Common


The brown egg laying breeds such as Australorps, Brahmas, Delawares, Orpingtons, New Hampshire and Rhode Island Reds, and Plymouth Rocks far dominate the average egg basket. These breeds possess brown pigment genes.

During the final hours of the laying process, these breeds apply a dark pigment called "porphyrin" to the outside of the eggshell.

The pigment is derived from hemoglobins and produced by the breakdown of red blood cells. This results in a brown-shelled egg. 

Different breeds have different amounts or shades of the pigment which accounts for some breeds like Australorps or Buff Orpingtons laying pale brown eggs, while Marans lay dark chocolate brown eggs.

Interestingly, the inside of a brown egg is always white – the brown dye doesn’t penetrate the shell, instead it sits on the outside of the shell.


And Then You Have Blue Eggs


There are only a few breeds that lay blue eggs. Three of them are Ameraucanas, Araucanas and Cream Legbars.

The blue color is created by a different pigment than the type that makes brown eggs. The blue pigment is called "oocyanin". 

It originates in the bile and is applied very early in the laying process. Because it's a different type of pigment and is applied so close to the onset of 26-hour laying process, the blue pigment goes right through the shell, unlike the brown pigment. So blue eggs are blue inside and out. 

Araucanas are a pure breed recognized by the American Poultry Association since 1976.

Ameraucanas are a pure breed recognized by the American Poultry Association since 1984.

Cream Legbar are a cross breed not yet recognized by the APA.



So What About Green Eggs? 


Green eggs are created by crossing a blue egg laying breed with a brown egg laying breed.

Olive Eggers are one such type of chicken which are bred by crossing a Marans with an Ameraucana. Green eggs are green on the outside and blue on the inside.

This is because the blue pigment is applied initially, seeps through the shell, and then is covered with the brown pigment. This results in a green egg. Varying amounts and shades of brown result in the various shades of green eggs.


Consider adding some colored eggs to your basket this spring! This handy chart can give you an idea of which breeds you might want to choose to achieve the colors you're looking for.

A Rainbow of Egg Colors


Visit the My Pet Chicken website to find lots of fun colored egg laying breeds.


Further reading:
http://www.virology.ws/2013/09/11/a-retrovirus-makes-chicken-eggshells-blue/
http://www.nytimes.com/2010/05/04/science/04qna.html
http://www.marthastewart.com/246734/backyard-chickens
http://www.fresheggsdaily.com/2013/12/ameraucana-vs-araucana-vs-easter-egger.html
http://www.fresheggsdaily.com/2012/02/rainbow-of-egg-colors.html


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