Chickens lay colored eggs naturally based on their breed genetics, specifically the pigments their bodies produce which are applied to the eggshell during its formation.
You get colored eggs from chickens because certain breeds produce pigments that are deposited onto or throughout the eggshell before the hen lays it. This isn't a result of diet or environment, but rather the specific genetic makeup of the chicken breed.
The Science Behind Egg Color
The color of a chicken egg is determined by the pigments produced in the hen's uterus as the egg is being formed. The base color of an eggshell is white, derived from calcium carbonate. Colors like brown, blue, or green are added layers or permeations of pigment.
According to sources, before hens lay their eggs, the pigment of certain breeds permeates the shell's exterior and lines the inside of the shell, too. This means the color isn't just a surface coating for all colored eggs; for some colors, like blue, the pigment is present throughout the shell.
For instance, Ameraucana chickens are well-known for laying blue eggs. This happens because they produce a pigment called oocyanin. This specific pigment is incorporated into the eggshell structure during its formation, meaning this pigment colors both the inside and outside of the shell. This is why a blue egg is blue all the way through the shell, not just on the surface like many brown eggs.
Common Egg Colors and Breeds
Different breeds produce different pigments or combinations of pigments, leading to a variety of egg colors.
- Brown Eggs: Result from pigments called porphyrins, derived from hemoglobin. These pigments are applied late in the shell-forming process, primarily to the exterior. Breeds like Rhode Island Reds, Plymouth Rocks, and Marans lay brown eggs (Marans lay dark brown).
- Blue Eggs: Result from the pigment oocyanin, which permeates the entire shell. Breeds like Ameraucanas, Araucanas, and Cream Legbars lay blue eggs.
- Green Eggs: Often result from a cross between a blue egg-laying breed and a brown egg-laying breed. The blue pigment is laid down first, and then brown pigment is layered over it, creating a green hue (e.g., Olive Egger crosses).
Here's a simplified look at some common egg colors and the pigments involved:
| Egg Color | Primary Pigment(s) | Pigment Application | Example Breed |
|---|---|---|---|
| White | None (Calcium Carb) | N/A | Leghorn |
| Brown | Protoporphyrin | Applied to exterior | Rhode Island Red |
| Blue | Oocyanin | Permeates entire shell | Ameraucana |
| Green | Oocyanin + Protoporphyrin | Blue permeates, brown on exterior | Olive Egger (Cross) |
Factors That Don't Determine Egg Color
It's important to note that a chicken's diet, the type of feed they eat, or their environment do not change the color of the eggs they lay. An Ameraucana hen will always lay blue eggs, regardless of what she eats. The color is purely a function of her breed's genetics and the pigments her body produces.
The color of the eggshell also has no impact on the nutritional value, flavor, or cooking characteristics of the egg inside. A brown egg is nutritionally identical to a white or blue egg of the same size and freshness.
In summary, colored eggs from chickens are a natural genetic trait, determined by the specific pigments their bodies produce and deposit onto the eggshell during its formation, sometimes permeating the shell entirely as is the case with blue eggs from breeds like the Ameraucana.
