How Do Eggs Get Fertilized in Chickens?

The Anatomy of a Chicken

Chicken AnatomySource:

Before we dive into the process of how eggs get fertilized in chickens, let’s first discuss the anatomy of a chicken. Chickens have a unique reproductive system that allows them to lay eggs regularly. The female chicken, known as a hen, has two ovaries, but only the left one is functional. The ovary produces an ovum or an egg yolk every 25 hours, which moves into the oviduct.

The Oviduct

Oviduct ChickenSource:

The oviduct is a long, convoluted tube that extends from the ovary to the cloaca, which is the opening where both feces and eggs are expelled. The oviduct is divided into five parts and each part plays a crucial role in the formation of an egg. The egg white, or albumen, is formed in the first part, while the shell membrane is formed in the second part. The third part is where the eggshell, the hard outer layer of the egg, is formed. The egg then moves on to the fourth part, where it receives a coating of “bloom,” a protective layer that helps keep bacteria out. Finally, in the fifth part, the egg is laid through the cloaca.

The Role of the Rooster


Now that we understand the anatomy of a chicken, let’s talk about the role of the rooster in fertilization. Unlike hens, male chickens, known as roosters, have both testes and a penis. The rooster’s testes produce sperm, which is stored in the seminal vesicles until it is ready to be transferred to a hen during mating.


Chickens MatingSource:

During mating, the rooster mounts the hen from behind and grabs her comb with his beak. He then stands on one foot and flaps his wings for balance while he inserts his cloaca, which has a penis-like organ called a phallus, into the hen’s cloaca. The sperm is then transferred from the seminal vesicles to the hen’s oviduct, where it can fertilize the egg.


Fertilized EggSource:

Once the sperm fertilizes the egg in the oviduct, the egg starts to develop. It takes about 24-26 hours for the egg to travel through the oviduct and be laid. If the egg is not fertilized, it will still be laid, but it will not develop into a chick. However, if the egg is fertilized, it will develop into a chick over the course of 21 days.

The Importance of Fertilization

Baby ChickSource:

Fertilization is crucial for the continuation of chicken life. Without fertilization, there would be no baby chicks and eventually, no chickens. Fertilized eggs are also important for those who wish to hatch chicks at home. However, not all eggs that are sold in grocery stores are fertilized, as commercial egg production does not always involve roosters.


Now that you understand the process of how eggs get fertilized in chickens, you can appreciate the importance of fertilization in the continuation of chicken life. Whether you are a backyard chicken keeper or just enjoy eating eggs, knowing this process can help you understand and appreciate the work that goes into producing the eggs we consume.

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