Eggs are one of the most versatile foods around. They can be the star of the show (omelette, quiche), the supporting actor to other ingredients (pad thai, spaghetti carbonara) or the hidden hero by making a cake rise or giving a soufflé its fluff.
Though they are ubiquitous in the culinary world, the process of how an egg forms inside a hen is not widely understood. An egg develops through multiple stages during its time inside a hen. A yolk is encased in layers of egg white and protective membranes, sealed within a shell and coated with a fast-drying protective fluid.
This page will help you find answers to some of the most popular questions about how eggs form inside hens.
How Long Do Hens Lay Eggs For?
The hen breeds used in commercial egg farming start laying eggs at around 16-18 weeks (four months) old. The first eggs laid by hens at this young age are relatively small at about 45-50 grams. But over a period of about three months, the egg size increases to an average of 60 grams.
Commercial laying hens continue to produce first quality eggs until they are about one and a half years old. After this, their eggs become fewer and shell quality decreases which leads to more cracking and breaking.
How Is an Egg Formed?
Here’s an outline of the amazing process of egg formation in a hen.
The Yolk – It starts with the yolk forming in the hen’s ovary. When the yolk reaches the right size, it is released into the oviduct, where the rest of the egg will form.
The White – In its journey through the oviduct, the next layer to be added is the egg white (albumen). This layer takes about 3 hours to be formed.
The Shell Membrane – The next layer to be added in the oviduct is the shell membrane. This takes about 1.25 hours. It is a very thin layer between the egg white and the shell, and it almost looks like tissue paper. Have you ever cracked an egg shell but the egg didn’t break? The shell membrane was still intact holding everything together.
The Shell – The egg then reaches the hen’s uterus, also known as the shell gland. This is where the shell is added to the egg. The shell is also formed in layers over the course of 19 hours, where pigment is also added. All egg shells begin as white. Blue and brown pigments are added during the shell forming process. The color of the pigment depends on the breed of chicken.
An interesting note about egg coloration. Brown pigment is added last in the formation of an egg shell. It is only found on the surface of the egg. When you crack open a brown egg, the inside of the egg shell will be white. Blue pigment is added early in the shell formation process. The color will penetrate the entire shell. When you crack open a blue egg, the inside of the shell will be blue. Green eggs are a combination of brown and blue pigments. White eggs contain no pigment at all.
The Bloom – The bloom is the protective layer or cuticle that covers the egg shell and is the last layer added in egg formation. It is added after the egg leaves the uterus, right before it exits from the hen’s vent. This coating seals out bacteria and maintains the moisture inside the egg. Leaving the bloom intact will help keep your eggs fresher, longer.
Please watch the video below for more information. Thank you for visiting our website! We hope you will find something of interest on our website. Watch the video in the below:
Video source: Pakistan Poultry Association