Hens don’t need a rooster to lay eggs, but they do need a rooster in order to lay fertilized eggs. Chickens are different from mammals in a lot of ways when it comes to their anatomy and therefore their reproductive system. Let’s talk about how eggs are fertilized by chickens.
When roosters mate with hens, they transfer their sperm through cloacal contact and not by penetration. The first fertile egg is laid between 36-48 hours after mating. A chicken lays an egg on the day it mates, but an egg laid three days later is fertile.
As a backyard chicken owner I often get questions from curious folks about how roosters fertilize eggs. It’s a fair question if you’re new to raising chickens! I’ll explain the process in simple terms in this article.
A Quick Intro to Chicken Reproduction
First let’s review some chicken biology basics. Hens are female chickens and roosters are male chickens. Hens have ovaries and oviducts where yolks and egg whites develop, and finally eggs are laid. Roosters have testes that produce sperm.
Rooster sperm must join with egg yolk in the hen’s oviduct so that an egg can become fertilized and grow into a chick.
How Mating Occurs
The fertilization process starts with mating. When a rooster mates with a hen here’s what happens .
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The rooster will mount the hen and rest his chest on her back while flapping his wings to maintain balance.
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Their cloacae (vent openings) make contact. The rooster’s cloaca releases sperm, which travels into the hen’s cloaca.
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The sperm then travels up to the hen’s oviduct, where it can survive for 2-3 weeks.
So essentially, the physical act of mating allows the rooster to transfer his sperm from his cloaca to the hen’s. The sperm gets stored internally and can fertilize eggs during the next couple of weeks.
When Fertilization Happens
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As a yolk travels down the hen’s oviduct over 24-26 hours, it may encounter live sperm stored from a prior mating.
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If sperm penetrates the yolk, fertilization occurs. The germinal disc on the yolk begins dividing into a cluster of cells that will become the embryo.
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The egg white forms around the yolk as it travels through the oviduct. Eggshell membranes are added in the uterus.
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Finally, the shell forms in the shell gland. At this point the egg is fully formed, and is laid through the cloaca 20-26 hours after the yolk’s release.
Signs of a Fertilized Egg
How can you tell if an egg is fertilized? Here are a few ways:
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To caramelize an egg, shine a bright light through it in a dark room. There will be a dark spot and a network of veins on fertilized eggs as the embryo grows.
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Open it up and look for a white spot on the yolk. This is the blastoderm, also known as the germinal disc. This is where the embryo starts to grow.
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Float test: Fertilized eggs tend to lie flat on the bottom when placed in water. Unfertilized eggs are more buoyant.
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Incubate it: If you incubate an egg for several days and don’t see embryonic development, it’s unfertilized.
Do Hens Need Roosters to Lay Eggs?
Here’s an important fact: hens can lay eggs just fine without a rooster around! The egg-laying process is automatic for hens that get adequate nutrition and daylight.
However, the eggs won’t be fertilized or hatch into chicks without a rooster’s contribution. Basically, roosters are necessary for fertilization but not for basic egg production.
In Summary
In chickens, fertilization occurs when sperm from the rooster penetrates the yolk inside the hen’s oviduct. This happens after mating, when the rooster transfers sperm into the hen’s cloaca where it’s stored. As yolks develop into eggs over 24-26 hours, some may encounter sperm and get fertilized. We can identify fertilized eggs by candling, cracking them open, floating tests, or incubating them to check for embryos. And hens don’t need a rooster simply to lay unfertilized eggs.
Do Fertilized Eggs Look Different?
Fertilized eggs do not look obviously different upon first examining them. Without cracking the egg, you can shine a light into the egg and see spider veins and a dark area if the embryo has started to develop. An egg that hasn’t been fertilized will look translucent.
You can look for the germ spot in the yolks of the eggs after they have been cracked open. The germ spot is a white circle just outside of the center of the yolk. A fertile egg will have a larger white spot with a clear space in the center. An infertile egg will have a smaller white spot. This can be hard to identify if you aren’t comparing a fertile yolk with an infertile yolk.
How Fertilized Eggs Develop Into Chicks
After a fertilized egg is laid, it will only develop into a chick if it’s kept warm. A hen doesn’t always want to incubate the eggs. This depends on a lot of things that we will talk about soon. It’s a big job! She will sit on the eggs for the majority of the day to keep them warm.
Incubating the chicken eggs yourself is a 21-day process that involves keeping the eggs at a certain temperature and humidity level, as well as turning the eggs!.
We already said that after a week of incubation, you can shine a light on them and see the veins and embryos starting to form.
If fertilized eggs aren’t incubated they won’t develop into chicks. A hen will look for a comfortable stress-free place to lay her eggs and incubate them. Nesting Pads are a great addition to the chicken coop.
How do chicken eggs get fertilized? *More Than You Ever Wanted To Know*
FAQ
How does a male chicken fertilize an egg?
Male chickens, or roosters, fertilize hen’s eggs through a process called the “cloacal kiss”. During mating, the rooster and hen briefly touch their cloacas (the single opening for reproductive and digestive tracts). This allows the rooster to transfer sperm to the hen.
Are rooster eggs good to eat?
Eggs that have been laid by a hen and rooster may have a blood spot on them, but they are still safe to eat and taste the same.
How many times a day does a rooster mate?
Are hens happier with or without a rooster?
In general though, most hens are perfectly happy WITHOUT a rooster present, especially if kept contained. Some roosters make good sentries, so if free ranging days, can warn of predators, which may help some free ranged hens feel safer???.