Understanding how eggs are formed offers fascinating insights into a hen’s reproductive system. When a hen reaches maturity, specific lighting conditions trigger hormonal changes that start the egg-laying cycle. Remarkably, a hen takes approximately 25 hours to produce an egg from start to finish. As soon as a hen lays one egg, it begins forming the next egg.
Eggs are one of nature’s most incredible creations. The process an egg goes through in a hen’s body is complicated, but it works well to make sure the egg has all the nutrients and protection a chick needs as it grows. This article will show you how an egg grows inside a chicken, step by step.
An Overview of Egg Formation
The hen’s ovary is where the egg yolks are released. They then travel to the oviduct to be surrounded by albumen, membranes, and a shell. It takes about 24 to 26 hours for a yolk to turn into a fully formed egg and for the hen to lay it.
The key stages of development are:
- Release of yolk from ovary
- Entry into oviduct
- Addition of albumen
- Addition of shell membranes
- Formation of the shell
- Egg laying
Even though the steps are set, breed, diet, age, lighting, and stress are just some of the things that can change the quality of the eggs and the rate at which they are produced. Now, let’s look at each stage in closer detail.
Step 1: Ovulation and Yolk Release
Formation starts when a yolk ovulates from the hen’s ovary. Hens have two ovaries, but only the left ovary is functional as an adult.
The ovary contains many small yolks, each surrounded by a follicle. When a follicle matures, it ruptures and releases the yolk into the oviduct in a process called ovulation.
The yolk is rich in nutrients like fats, proteins, vitamins and minerals which will nourish the developing chick embryo. Pigments from the hen’s feed, especially yellow/orange plant pigments, give the yolk its colorful appearance.
Step 2: Entry into the Oviduct
The newly released yolk is grasped by finger-like structures called fimbriae at the entrance of the oviduct. It enters the first part of the oviduct called the infundibulum.
This is where fertilization happens if sperm are present. In egg farm and backyard flocks, hens are not mated so the yolk continues unfertilized.
Step 3: Adding the Albumen in the Magnum
From the infundibulum, the yolk travels to the magnum portion of the oviduct. Here it spends 2-3 hours while the albumen, or egg white, forms around it.
The albumen is mostly made up of water and proteins that are released by cells that line the oviduct. First, thin albumen forms. Then, thick albumen forms closest to the yolk, which keeps the yolk in the middle.
The albumen provides hydration, nutrition and shock absorption for the growing embryo.
Step 4: Forming the Shell Membranes
After the albumen layers are complete, the egg moves to the isthmus. Here the shell membranes are added. The inner and outer membranes are made of thin protein sheets.
These membranes cushion the egg, allow gas exchange, and provide an optimal environment for the developing chick. They also act as a barrier to keep out bacteria.
Step 5: Creating the Eggshell
The last major stage is the formation of the shell in the shell gland pouch. This takes approximately 20 hours, during which calcium carbonate is deposited on the membranes to build the hard shell.
The shell is made of crystalline calcium carbonate primarily sourced from the hen’s feed. A cuticle also forms on the surface of the shell to seal pores and block bacteria.
The pigments that give shells their speckled brown or blue color are added as the last layers. When complete, the shell comprises about 10% of the egg’s total weight.
Step 6: Egg Laying
In the final stretch, the egg travels down to the vagina where it rotates slightly to position itself blunt end first. Powerful muscular contractions push the egg outward, and the hen lays the egg through the cloaca.
The cloaca is a shared exit for the digestive and reproductive tracts. As the egg is laid, it is coated with a protective bacterial barrier called the bloom.
The Cyclic Nature of Egg Formation
A hen’s body is primed to start forming the next yolk almost immediately after laying an egg. Ovulation occurs 30 minutes to 24 hours after laying, meaning the cycle repeats about once a day.
Egg production is an energy intensive process. For commercial breeds, peak lay occurs around 30-40 weeks of age. As hens mature, egg quality and production gradually decline.
Factors Influencing Egg Quality
While egg formation follows a consistent biological process, many factors influence the quantity and quality of eggs produced.
Breed
Some breeds are genetically better egg producers. Breeds like Leghorns and Australorps are optimized for high egg yields versus meat production.
Feed and Nutrition
Balanced nutrition provides the building blocks for quality eggs. Key nutrients include calcium for strong shells, protein for albumen, and pigments like xanthophylls for vibrant yolk color.
Age and Molting
Younger hens lay more frequently. Production declines as hens enter their second year and molting becomes more frequent.
Day Length
Increasing day length in spring triggers an increase in ovulation and egg production. Supplemental lighting helps extend the productive laying period.
Stress
Heat, overcrowding, noise and disease cause stress than can suppress ovulation and egg production. Minimizing stressors supports sustained, healthy egg yields.
Overall Health
Good general health and freedom from diseases like infectious bronchitis directly impact egg numbers and quality.
Appreciating the Incredible Egg
The intricate sequence of events inside the hen’s body produces one of nature’s most perfectly packaged foods. Each egg is uniquely equipped to nourish and sustain life. Understanding the physiology behind this 24-hour production cycle can deepen our appreciation for the humble egg.
So the next time you crack open an egg, take a moment to marvel at the biological perfection before you!
The Process of Egg Formation
Eggs are created in sequential layers from the inside out. Here’s a detailed look at each stage of this incredible process:
The process begins with the formation of the yolk within the hen’s ovary. The ovary sends the yolk into the oviduct when it’s the right size. This is where the rest of the egg grows.
How Eggs Are Formed
Understanding how eggs are formed offers fascinating insights into a hen’s reproductive system. When a hen reaches maturity, specific lighting conditions trigger hormonal changes that start the egg-laying cycle. Remarkably, a hen takes approximately 25 hours to produce an egg from start to finish. As soon as a hen lays one egg, it begins forming the next egg.
How EGGS Are Formed Inside The Chicken?
FAQ
How do chickens lay eggs if they don’t mate?
Hens do not need a rooster in order to create and lay eggs. All they need is a safe place, time, and a healthy diet with enough protein and calcium to form healthy eggs. Of course, any eggs laid by a hen where no rooster is present are going to be unfertilized, and therefore will never hatch.
How does an egg form into a chicken?
The embryo starts to grow on one side of the yolk. The yolk is held in place in the middle of the egg white by something called the chalaza, which is a protein cord. Blood vessels are present, and the embryo has a heartbeat. After five days, there is substantial growth and the tiny chick has an eye.
What causes a chicken to lay an egg?
A chicken lays an egg because of a complicated biological process that is set off by several things, mostly changes in hormones and daylight. When a hen reaches maturity (around 18-22 weeks), light stimulates her pituitary gland, releasing hormones that initiate ovulation.