Egg size is dependent on breed, age, and weight of the hen. Larger chicken breeds tend to lay larger eggs; bantam breeds lay small eggs. Older hens tend to lay larger eggs than younger hens.
The shell colour is a breed characteristic. Most chicken breeds lay light-to-medium brown eggs. A few breeds lay white, dark brown, green, blue, or cream coloured eggs. Shell colour is only “skin deep”- the eggs inside are the same as eggs of other colours.
The shell color intensity of eggs laid by one hen can vary from time to time, with an occasional darker or lighter eggshell.
A normal fresh egg has a yellow yolk, a layer of thick albumen (egg white) surrounding the yolk, and a thinner layer of albumen surrounding that.
At opposite sides of the yolk are two chalazae, short white twisted strands of albumen that anchor the yolk to the white. A large chalaza does not indicate embryo development.
Every egg yolk has a white disc called a blastoderm. It is usually visible but may be very pale. In an infertile egg, the blastoderm is solid white. In a fertile egg, the disc has a faint or distinct ring that makes it look like a donut or bulls-eye.
Fresh fertile eggs collected daily will not have embryos in them. Embryos do not begin to develop unless the eggs are in a favourable warm environment under a broody hen or in an artificial incubator.
The yolk of a chicken e
gg may be any shade from pale yellow to orange, depending on what the hen has eaten. The colour is usually consistent if hens are fed only one type of feed, but foraging hens and those fed kitchen scraps will often produce a variety of yolk colours.
The egg yolk or egg white may have red or brown specks in it. These “blood spots” and “meat spots” are harmless bits of tissue.
An eggshell has a protective coating that prevents bacteria from entering the egg. To retain this coating, eggs should not be washed until just before use.
If you aren’t sure how old an egg is, you can submerge it in water. The freshest eggs will remain at the bottom of the container, while old eggs will float. Floaters should either be discarded or opened far from your nose.