If you have raised chickens before, or have purchased chicken eggs from the stores, you would clearly see that most of the time, the eggs are brown or white on the outside.
However, the eggs’ color isn’t always white or brown. Some chicken breeds can lay blue eggs. So why do chickens lay blue eggs? What gives the blue eggs their color? What breed lay blue eggs?
Why do chickens lay blue eggs?
Some chicken breeds can lay blue eggs because the retrovirus goes into the chicken genome. This activates a gene that leads to the production of blue eggs.
Blue eggs
Some of the chicken breeds that lay blue eggs include the Araucana from Chile and the Dongxiang and the Lushi from China.
An autosomal dominant gene controls the blue eggshell color. Eggs produced by the heterozygotes are a lighter blue than those from homozygote chickens.
The gene oocyan (O) is responsible for causing blue eggshell color. Previously, it was mapped to the short arm of chromosome 1.
This dye is different from the brown pigment found in brown eggs. Since it is applied very early during the laying process, the dye goes through the shell, so the blue eggs are blue inside and outside.
White color is the start of all eggs
While the egg is developing inside a hen’s body, no matter what breed lays the egg, the eggshell will start out as white color. The shells are made mostly out of calcium carbonate (CaCO3).
The calcium used to create the eggs can come from chicken layer feed, crushed oyster shells or eggshells, and some other food that is rich in calcium.
It doesn’t matter what color of the egg finally ends up being or what breed the chicken is, the eggshell will always be white as the egg travels down the hen’s oviduct.
With some breeds like the Andalusians, the Catalanas, the Lakevelders, the Leghorns, and more, they will lay white eggs at the end simply because they don’t have any pigment genes.
Brown eggs – the most common color
Some brown egg-laying breeds include the Australorp, the Brahmas, the Orpingtons, the New Hampshire, the Delawares, the Plymouth Rocks, and the Rhode Island Reds.
If you buy eggs from the stores, the eggs from those breeds will most likely be in your egg basket. Their eggs are brown as they have brown pigment genes.
Those breeds apply a dark pigment to the outside of the eggshell when the laying process ends in a few hours. The pigment is called “porphyrin.
The pigment is the result of breaking down the red blood cells, so it is derived from hemoglobin.
The amount and shades of the pigment can vary from breed to breed. For example, the Australorps or the Buff Orpingtons lay pale brown eggs, while breeds like the Marans lay very dark brown eggs.
Whenever you crack a brown egg, you will notice that the inside of the egg is always white. This is because the chickens only dye the outside of the eggshell; the dye doesn’t penetrate the eggshell.
Do blue eggs taste different from other types of eggs?
Blue eggs next to other types of eggs
This may be surprising, but blue eggs don’t taste any different than white eggs and brown eggs. Since the pigment only affects the shell of the egg, the eggs’ interior taste and look the same as brown and white eggs.
So the next time you shop for eggs in the store, just treat them as any other eggs. If you want a way to cook the eggs and preserve the egg color at the same time, you can boil the eggs.
Are blue eggs healthier than other types of eggs?
All eggs are similar when it comes to nutrition. A normal egg contains lots of minerals, vitamins, and high-quality protein. Those nutrients come with less than 80 calories.
But, there are many studies indicating that the color of the eggshells has no significant effect on the nutrition of the eggs. That means blue eggs are just as healthy as brown or white eggs.
Instead, these are the factors that can affect the eggs’ quality:
- The hens’ environment: if your hens are allowed to go around in the sunshine, you can expect their eggs to contain 3 to 4 times the amount of vitamin D compared to if you only let them be inside the coop.
- The hens’ diet: if you want your hens to produce omega-3 fatty acids-rich and vitamin D-rich eggs, you can feed them diets that are rich in those nutrients.
Read more: How do chickens lay eggs without a rooster?
How are green eggs created?
Green eggs are the result of crossing a brown egg-laying breed with a blue egg-laying breed. One of the examples is the Olive Eggers, which is the result of crossing the Marans and the Ameraucanas.
Green eggs’ shells are not green all the way. They are green on the outside but blue on the inside.
This is because, during the development of the eggs, the blue dye is applied first. And as it penetrates through the shell, the shell is covered with brown dye, which creates a green color.
Since the brown eggs have different amounts and shades of brown, the outcome green eggs will also have multiple shades of green.
Conclusion
So, why do chickens lay blue eggs? The color of the eggs is dependent on the chickens’ breed. The retrovirus in those breeds triggers a gene that leads to the production of blue eggs.
The blue color is created with the pigment gene oocyan (O), and the way it works is very different from brown eggs.
For brown eggs, the pigment is applied outside of the eggshells and doesn’t penetrate the eggshell. The blue pigment is applied very early and goes all the way through the eggshell.
Resources
Image credits – Photo by Autumn Mott Rodeheaver, Samuel Isaac on unsplash.com