How do chickens lay so many eggs?


I’ve heard chickens can lay eggs every 1-2 days. It baffles me that something so (relatively) big can come out of them so often. How do they produce so many with such limited internal space? How many are developing in them at any given time?

In: 2833

If you’ve ever slaughtered a laying hen, you will see a production line of yolks coming out of their ovaries, getting progressively larger and larger as it gets closer toward the cloaca. So a chicken that lays an egg on one day will have a yolk that’s almost fully formed ready to get wrapped up with albumen and a shell the next day or two. Chickens need to eat pretty constantly all day to keep up with the resources it needs to do this. It really is a marvel, but we’ve bred them to do exactly this.

They’ve been selectively bred to produce such a large number of eggs. This also takes a toll on their bodies and can cause serious health problems.

See [Cage Layer Fatigue](

Most wild fowl has a laying season and can lay an egg a day in that season. Chickens are domesticated and bred to lay for more of the year. Even still a breed that lays an egg a day will have about a 2 month period of not laying anything while they molt. But artificial light, warm, and steady food supply encourage a longer egg laying season then the same chicken would have in the wild.

Others have covered how it works biologically for modern chickens, but it is also interesting to understand how the ability to lay so many eggs evolved.

The answer? **Bamboo**

Wild chickens are from SE Asia where they have a lot of bamboo. The bamboo will infrequently drop a bumper crop of seeds. This is essentially chicken feed.

These birds evolved the ability to constantly lay eggs during the short time when the food supply was plentiful. Locals then realized that providing a constant food supply would cause the birds to lay daily all year long.

Here is a fun animated [YouTube lesson on the topic](