All About Double Yolk Chicken Eggs

What is a double yolk egg? It's simply a single-shelled egg with two yolks inside and it's not as uncommon as you might think.

Odd Eggs Happen

Buying eggs from the grocery store has given so many of us a distorted reality of the way chickens actually lay eggs. There all the eggs are uniformly sized, perfectly colored and have no oddities. (Commercially, odd eggs are used in food where they can’t be seen such as baking and cake mixes.)

In reality, there can be lots of odd eggs laid by a hen over the course of her lifetime, especially if she's a good egg layer. Most of them are edible and perfectly fine to eat. Think about it, hens can lay a thousand or more eggs in their productive years. The mathematical odds of something being perfect every time are low, if not impossible.

Statistically speaking, double yolk eggs happen in about one in every thousand eggs. They are more common in hybrid and large breed chickens and can be hereditary. In some countries, hens that lay double yolk eggs are prized and bred to lay them.

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What Causes a Double Yolk Egg? 

Hens are hatched with all the eggs they will ever be able to lay already inside them. The yolks are contained in the hen’s left ovary, which is her only working ovary. Once the hen is of laying age, individual yolks will mature and be released into the oviduct. They are kind of like a production line, where each is in progress, just one at the head of the line that's maturing faster. It takes a hen 26 hours or so to form and lay an egg. Then about an hour after laying, another mature yolk will be released and start going through the egg formation process. Double yolk eggs or in rare cases, triple yolk eggs, are formed when the hen releases two or more yolks at once. They move through the reproductive tract and are encased by a single shell.

How Can You Tell an Egg Has a Double Yolk Inside?

Knowing whether an egg has a double yolk inside isn't always possible, but the size is the biggest indicator. Most times double yolk eggs will be much bigger than a standard size egg; double and even triple the size. Ouch!

Is There a Time When Double-Yolk Eggs Are Likely to Happen?

Double yolk eggs often happen as chickens begin their laying cycle. At that point, a hen’s body is starting to get into a rhythm, and as with any rhythm, it can be hard to pick up the beat every time.

Double yolk eggs can also happen at the end of hen’s laying cycle as things are winding down causing that rhythm to be thrown off beat.

Do Double-Yolk Eggs Mean My Hen is Sick?

You may find that double yolk eggs can mimic chickens laying soft eggs. In reality, the same amount of calcium goes into a double yolk eggshell as goes into a standard size shell. Because the shell is bigger without extra calcium, you may find your double yolk eggshells a little softer than normal.

Soft eggs are not always a sign of sickness, although a hen regularly laying soft shelled eggs should be monitored as this can be a sign of infectious bronchitis and oviduct issues such as salpingitis.

A soft egg is often caused because of warm weather or because your hen needs more calcium in her diet. For warm weather, just make sure your hens have adequate places to get out of the direct sunlight such as under trees, shrubs or decks and have plenty of accessible fresh water. For inadequate calcium, it’s a good idea to feed your chicken’s eggshells back to them. You can clean them and then crush them up into small pieces and offer them free choice in a bowl or treat container. You should always make sure to feed a well-balanced layer feed to your flock and you can add supplements to help with consistent egg laying.

Can Laying a Double-Yolk Egg Hurt My Hen?

Double yolk eggs can cause problems for the laying hen. Consistent laying of extra large eggs can lead to egg binding, where the chicken cannot pass the egg and it’s stuck inside or prolapse where part of the oviduct is sticking out of the chicken’s vent on the outside of her body.

Ultimately, a double yolk egg or other odd eggs, happen during the productive years of a laying hen and they’re nothing to worry about. We shouldn’t expect a hen to lay a perfect egg every time she lays. But, if you get a lot of odd eggs consistently from one hen or from many flock members then it may be a clue that something is wrong.