Eggs wonder why chicken eggs are laid in different colors, shapes, shades


Have you ever been curious to know why chicken eggs can be different colors? Although most eggs are white or brown, they also come in colors like cream, pink, blue, and green. What’s more — and it’s not “yellow” — some are even speckled. Nature has provided chickens with various color patterns for their feathers, skin patches, and eggshells for a variety of purposes including camouflage, protection from predators, and to signal individual identity.

According to a Texas A&M AgriLife Extension Service A specialist in poultry, the color of an egg is mainly determined by the genetics of the hen. This means that the breed of hen will usually indicate the color of the egg that will be produced. For example, Leghorn hens lay white eggs, while Orpingtons lay brown eggs, and Ameraucanas lay blue eggs. And the “olive egger” breed lays, wait for it, olive green eggs.

But appearances aside, not all chicken eggs have major differences in taste or nutritional composition.

Chicken earlobes help predict egg color

You must hear this, a good way to guess the color of eggs a hen will lay is to take a look at the hen’s earlobes.

“In general, hens with white earlobes will produce white eggs,” said Gregory Archer, Ph.D., AgriLife Extension’s specialist in the Poultry Science Department, Bryan-College Station. “But all eggs start out white because the shells are made of calcium carbonate. They get their color from the genetics of the hen when the egg is forming.

Archer said chickens with lighter earlobes more often also had white feathers and produced white eggs. Those with colored feathers and darker earlobes will likely produce colored eggs.

Image by Stephanie Frey, Shutterstock

Formation of chicken eggs

Nature has its own way of coloring eggs, and it doesn’t need boiling water, food coloring or paintbrushes. Let’s see how this happens. Different eggshell colors come from pigments deposited on the shell when the egg is formed in the hen’s oviduct. The oviduct is a tube-shaped organ located along the spine of the hen between the ovary and the tail.

A chicken yolk, or egg, forms in the hen’s ovaries. A fully formed egg leaves the ovary and enters the oviduct. There, he goes through a five-step process to ensure the yolk makes it safely to the outside world. The whole process of egg formation usually takes just over 24 hours.

It is during the fourth stage of this process involving the shell gland that pigments are deposited on the shell, producing its color. So, in short, different breeds of chicken deposit different pigments on the shell as it forms, changing the color of its outer – and sometimes inner – shell.

A pigment of your imagination

White Leghorn chickens lay eggs with white shells and breeds like Plymouth Rocks and Rhode Island Reds lay eggs with brown shells. The shells are brown because a pigment known as protoporphyrin is deposited on the shell. But since this happens late in the shell formation process, the pigment does not penetrate inside the shell.

“That’s why when you open a brown egg, you’ll see that the inside of most of the shells remains white,” Archer said.

A pigment called oocyanin is deposited on the egg of the Ameraucana race, penetrating both the outside and the inside of the shell and turning them blue. Other breeds such as Araucana, Dongxiang and Lushi lay blue or blue-green eggs.

Image by Laura McKenzie/Texas A&M AgriLife Marketing and Communications

An olive egger results from a cross between a hen and a rooster of a brown-laying breed and a blue-laying breed. The hen produces a brown pigment which penetrates the blue shell of the egg, resulting in a greenish colored egg. The darker the brown pigment, the more olive-colored the egg appears.

Other chickens that lay colored eggs include the Easter Egg, Barred Rock, Welsummer, and Maran, with egg color depending on the breed and its genetics.

“I believe Easter eggs lay the most fun and interesting eggs,” said Garrett Webb, a Texas 4-H member of Fancy Feathers 4-H, which is part of the Kyle 4-H club. “Each bird lays a different colored egg. Eggs can be blue, green, pink, or a blue-green mix.

Webb, who is the director of this year’s Fancy Feathers Poultry Show, said the Easter Eggs are Ameraucana or Araucana mixed breeds.

“Easter eggs can be any other breed mixed with one of these two main breeds,” he said. “A hen only lays one color of egg all her life. It does not change colors. If she starts laying blue eggs, her eggs will always be blue.

Some speculation about speckled eggs

It turns out that the spots on the speckled eggs are just extra calcium deposits. One of the reasons for the speckled egg show is that speckles form when the calcification process of egg formation is disrupted. Another possible reason is a defect in the shell gland. Again, this could be the result of excess calcium in the hen’s system. Sounds a bit confusing to you? Don’t worry, just keep your sunny side up and know that there’s probably more than one explanation for this speck-tacular event.

Oh, and while technically considered “abnormal”, speckled shells have sometimes proven to be tougher than regular shells.

Image by litchima, Shutterstock

Egg-related factors change shell color and shape

Although genetics primarily determine egg color, other factors can also influence color and other shell characteristics. These factors include the age of the hen, diet, environment and stress level.

“As they age, hens that lay brown-colored eggs may begin to lay larger, lighter-colored eggs,” Archer said. “But while this may produce an egg of a lighter or darker shade, it will not alter the base color of the egg.”

Although not directly associated with color, an oddly shaped or irregularly shaped egg can sometimes appear. This may result from a problem during the hen’s egg formation process.

Archer said very old and very young hens are most likely to lay abnormally shaped eggs. “Stressors like illness, heat or overcrowding can also affect the hen and impact egg size, shape and quality,” he said. “It also depends a lot on how much calcium the hen has in her body and can support the egg-making process.”

Everything Yellow: Color, Nutrients, and Double Yellow

You may also be wondering if the color of the egg affects the color of the yolk. Well, it doesn’t, but the hen’s diet certainly does. For example, if a pasture-raised hen eats plants with yellowish-orange pigmentation, the yolks may take on a more orange color. If she eats primarily a corn or grain-based diet, the yolk is more likely to be pale yellow.

Here is a little information about eggs for you. Research shows that darker, more colorful yolks contain the same amount of protein and fat as lighter yolks. However, studies showed that pasture-raised eggs may contain more omega-3s and vitamins as well as lower cholesterol.

Speaking of yolks, this will crack you up – sometimes an egg will have two yolks. While some people think a double yellow is good luck, the reason is more accident than fortune. A double yolks is a fluke that occurs when a hen ovulates too quickly, releasing two yolks, usually about an hour apart. These yolks enter the oviduct and eventually end up in the same shell.

Hormonal changes or an overactive ovary will also cause these double releases. These “double yolks” are more common in young chickens because their reproductive system is not yet fully developed.

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