Hens don’t need a rooster to lay eggs, but they do need one to lay eggs that have been fertilized. The bodies of chickens and mammals are very different, which means that their reproductive systems are also very different. 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. So an egg laid the day the chickens mate won’t be fertile and an egg laid three days later is fertile.
Chickens are wonderful animals that give us healthy eggs and meat. Many people don’t understand how a chicken gets pregnant and lays eggs, though. I’ll explain in simple terms how chickens have babies in this article.
Overview of Chicken Reproduction
A chicken must mate with a rooster in order to get pregnant and lay fertilized eggs. Without a rooster, hens can lay eggs, but the eggs won’t be fertile. Here’s a quick rundown of how it works:
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Hens start producing eggs around 18-20 weeks old They don’t need a rooster to lay eggs.
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When a rooster mates with a hen, the egg inside her gets fertilized. The egg can now grow into a chick.
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It takes 24-26 hours for an egg to form inside the hen after mating occurs.
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A fertilized egg forms a chick embryo after about 3 days if incubated
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Chicks hatch after 21 days of incubation.
Now let’s get into the details…
How Mating Occurs
A rooster must mate with a hen for fertilization to take place. Here’s how it happens:
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The rooster will grab the hen’s comb with his beak and position her.
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He lifts his tail and lowers his back to align his vent (cloaca opening) with the hen’s.
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The cloaca is the single opening chickens use for urination, defecation, and reproduction.
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The rooster contracts his cloaca to force his semen into the hen’s vent.
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The sperm then travels up the oviduct to the infundibulum where fertilization happens.
Egg Formation
24-26 hours after a hen is mated, an egg starts forming inside her oviduct. Here are the key steps:
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Infundibulum: This is where fertilization happens. The sperm meets the ovum and a zygote is formed which will become the embryo.
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Magnum: Over the next 3 hours, albumen (egg white) is formed around the zygote.
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Isthmus: The egg next moves to the isthmus where the inner and outer shell membranes are added.
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Uterus: In the uterus, the egg spends 20 hours developing a hard calcium carbonate shell.
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Vagina: Pigments and bloom are added to the shell in the vagina.
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Cloaca: Muscle contractions move the egg from the vagina into the cloaca prior to laying.
The whole egg formation process takes around 24-26 hours total. Amazingly, hens ovulate almost daily, allowing them to lay an egg nearly every day.
Incubation and Hatching
If a rooster has fertilized the eggs, chick embryos will develop under proper incubation:
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At 3 days, distinct red blood cells appear.
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By day 5, eye sockets form.
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By day 8, the legs and wings are visible.
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Around day 13 the chick’s gender becomes apparent.
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Days 15-21 the chick turns and gets into position for hatching.
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On day 21, the fully developed chick uses its egg tooth to pip through the shell and breathe air.
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Over 12-24 hours it fully emerges from the shell!
Eggs need consistent 99.5°F temperature and humidity levels around 50-65% in order to hatch after 21 days.
Benefits of Having a Rooster
While hens don’t need a rooster to lay eggs, having one does offer benefits:
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Fertilized eggs allow you to hatch chicks and grow your flock.
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Roosters will mate with hens repeatedly to ensure fertilization.
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Roosters provide protection and alert hens to food sources.
However, they can be aggressive and noisy, so weigh the pros and cons of having a rooster. Some communities prohibit keeping roosters due to noise.
What Mating Looks Like
Before a rooster mates with a hen he will prance around her and cluck. When he mounts the hen, he bends his tail down and the hen will lift her tail up. The cloaca vents will press together and the rooster injects his sperm.
Do Fertilized Eggs Look Different?
Fertilized eggs do not look obviously different upon first examining them. If the embryo has begun to grow, you can shine a light into the egg without breaking it open and see spider veins and a dark spot. An egg that hasn’t been fertilized will look translucent.
When comparing the yolks inside of the eggs (after cracking them open), you can look for the germ spot. 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 do chicken eggs get fertilized? *More Than You Ever Wanted To Know*
FAQ
How does a rooster make a chicken pregnant?
The rooster fertilizes the egg by mating with the hen. However if the egg is layed yet the rooster did not mate with the hen, then the egg will be infertile. With the egg infertile the rooster will not care to take care of it.
How do chickens lay eggs without a rooster?
Hens will lay eggs whether or not a rooster is present. The rooster’s role is solely for fertilization; without one, the eggs will simply be unfertilized.
How does the rooster fertilize the egg?
A rooster fertilizes a hen’s egg through a process called a “cloacal kiss” where the rooster transfers sperm to the hen’s cloaca during mating.
Do chickens need a rooster to get pregnant?
Without a rooster, your hens’ eggs are infertile, so won’t develop into chicks.May 13, 2025