Backyard Poultry

How Do Chickens Lay Eggs? Understanding Your Egg-Laying Chickens

Flock Management : Layer Nutrition

Flock Management : Egg Benefits

Flock Management : Egg Production

Patrick Biggs, Ph.D.

Nutritionist, Companion Animal Technical Solutions

Most flock raisers will tell you there’s something special about walking to the backyard and grabbing a few eggs for breakfast. Farm fresh eggs are protein-packed gifts from your chickens that thousands of families across the country have come to love. 
But how often do chickens lay eggs? And how do chickens lay eggs? The magic behind each farm fresh egg is a 24-to-26-hour process, with much of the work happening overnight. At their peak, laying hens can lay up to one egg per day.

Can chickens lay eggs without a rooster?

First, let’s answer a common question: Can chickens lay eggs without a rooster? Your egg-laying chickens will lay eggs with or without a rooster in your flock. Without a rooster, your ladies’ eggs are not fertilized, so they will never develop into chicks. If you have a rooster, the eggs could be fertile and need to be collected daily as well as stored somewhere cool, so no embryos begin to develop.

How do chickens lay eggs? How do chickens make eggs?

The biggest involvement for the laying hen is creating the eggshell. The shell defends the yolk from harmful bacteria and keeps the chick or yolk safe. Hens spend much of the egg formation process making sure the calcium-rich shell is strong and protective. When the lights are off and the hens are sleeping, that’s when most of this internal work happens.
The fact that shells are created at night is clear when looking at the egg formation timeline. For example, if a hen started the process at 7 a.m., she would create the eggshell starting around 12 p.m. and continue for 20 hours during the evening and through the night.
Hens are sleeping at night and not eating, which is why both large particle and small particle calcium are important. All Purina® premium layer feeds are infused with the Oyster Strong® System to ensure your laying hens achieve a consistent supply of large- and small-particle calcium through a blend of oyster shell, vitamin D and manganese. These three ingredients work together to help your chickens produce strong-shelled, delicious eggs each day.
Want more details about how eggs are made? Here’s an approximate timeline of the process:

Yolk release (1/2 hour):

Each female chick is born with thousands of immature yolks, known as follicles. For most chickens, follicles begin to develop into yolks when the hen reaches 18 weeks old. Once a follicle is selected to develop, it spends the next 10 days growing on the ovary and becoming a yolk. When it is time for the yolk to be released, it breaks out of its protective membrane and drops into the infundibulum or the beginning of the oviduct. This release takes about half an hour.

Initial egg white is created (3 hours):

 As the yolk enters the hen’s reproductive tract, the final protective layer of the yolk, the vitelline membrane, is added and the first layer of egg white (or albumen) begins to form around the yolk. As the yolk enters the magnum, layers of thick albumen are added. As the contents travel down the oviduct, they spin. This spinning motion causes the formation of the chalazae or the white, stringy pieces you see in an egg. The chalazae’s role is to keep the egg yolk in the center of the egg instead of sticking to the shell. 

Egg shape is formed (1 hour):

Just before the egg enters the shell gland, it spends an hour in the isthmus. While there, the inner and outer shell membranes are added around the albumen and the contents begin to take on the oval shape you expect.

Eggshells are formed (20 hours):

The most significant piece of the egg formation process happens in the uterus or “shell gland” of the hen. The developing egg spends about 20 hours in the shell gland where the shell is formed, and eggshell color is added during the last 5 hours.

Shell formation takes the most time to complete. It’s important the hen is fed a diet containing the proper nutrition, so she has the nutrients she needs to make the eggshell as strong as possible. A solid shell is the best defense against bacteria trying to get inside the egg.

Eggshell formation requires the hen to eat about 4 grams of calcium each day so that the 2 grams of calcium needed for the shell can get to the shell gland. Hens that are not getting enough calcium in their diet typically produce soft or brittle eggshells. Sometimes an improper calcium balance can cause hens to pull calcium from their bones to produce eggshells, weakening their overall skeletal structure.
In breeds that lay colored eggs, pigments, called porphyrins, are secreted from cells within the shell gland to add color to the eggshells during the last 5 hours of shell formation. Blue egg layers add pigment early in the shell formation process, which is why these shells are blue all the way through. A combination of blue and brown pigments produces a green shell color, as with an Olive Egger hen. Hens that lay white eggs do not produce any pigments during shell formation.

Egg bloom is added, and egg emerges (seconds):

The formed egg travels to the vaginal area where egg bloom is added to the shell as the egg passes through. Egg bloom, or the cuticle, is a protective coating that works with strong shells to protect the egg from bacteria. A natural lubricant is also added to the shell for a safe exit through the cloaca.

About 30 minutes after laying an egg, the next yolk will be released from the ovary and the process will repeat itself until she has laid 8 to 12 eggs. After that, she will take a day off from egg production and will start laying eggs again. To help the process go smoothly and to keep hens healthy and productive, always provide your hens a complete layer feed. After all, the formation of nutritious eggs is contingent on what your birds eat.
Give your hens everything they need to lay strong and stay strong with Oyster Strong®Sign-up for our Feed Greatness® Challenge and receive $6 worth of feed coupons.

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