This week, I’d like to discuss a very unusual occurrence shared by reader, Sandy Elgert…
“Dear Duncan and Wendy, I went to gather the last Thursday, and this giant egg was there. My chickens are Rhode Island Reds and Australorp. The egg had 3 yolks in it. It was super-sized, for sure! Is this normal to get eggs that big? The chickens were all ok, but I’m sure it was hard to pass! Do you know what could have caused it to be so big? I just thought I’d share this news with all of you guys.” ~ Sandy Elgert
Sandy sent us pictures of a super-sized egg laid by one of her hens. This egg had 3 yolks!
So this raises the question; why do chickens lay eggs with more than one yolk?
Let’s start with a quick reminder of how an egg is formed. You can find an extensive explanation on the formation of the egg in Vol 2: Issue: 2 – Wednesday 28th January 2009.
The hen’s reproductive system is made up of an ovary and an oviduct. A mature ovary, which looks like a cluster of very small grapes, may contain up to 4,000 small ova. Each of these ova can develop into a yolk.
About 7-9 days before ovulation, hormones cause an ovum to develop in sequence to a yolk.
Each yolk is attached to the ovary by a thin membrane with a fine network of blood vessels.
Generally, a yolk is released every 23 hours in a hen that is a very good layer. Less frequent layers do not ovulate as often.
The ovum travels through the hen’s reproductive system in sequence and a complete egg is formed. The final stop is the “Shell Gland” where the hard outer shell is added. The egg will spend 20 hours in the shell gland, the majority of it’s time in the reproductive system. Finally the “bloom”, or protective coating, is added as the egg is laid.
A double yolked egg is formed when two yolks are released either at the same time or in rapid succession.
Another cause is when the first yolk remains too long in the oviduct and is joined by a second yolk.
In either case, both yolks are encased within the same shell.
This unsynchronized release of yolks most often occurs in pullets, just coming onto lay.
Sometimes it takes a little while to get the hang of things.
In a particular hen, you may also find double yolked eggs to be a regular occurrence even as they become more mature. Some hens and some breeds are more likely to be genetically predispositioned to lay double yolked eggs.
The likelihood that a mature hen will lay a double yolked egg without this genetic predisposition is about 1 in 1000.
Sandy, I can’t even find a statistic for triple yolked eggs, it must be awfully rare!
There are a few characteristics that might indicate you have an egg with more than one yolk.
First of all, as you can see in Sandy’s pictures; these eggs are definitely larger than a typical single yolked egg.
Secondly, multi-yolked eggs are usually longer and thinner than a regular egg.
If you get a large egg and are wondering which hen laid it, just look for the one that is walking funny.
Okay, I’m just kidding.
Realistically speaking though, it can’t be comfortable to lay such a big egg. It is probably comparable to a woman giving birth to a 11 pound baby.
Large eggs will often have some blood on the outside of the shell, indicating either scraping of the lining or possibly a small tear in the vent area. It is not a concern unless it is a regular occurrence. In that case, you’d want to have your hen checked by a veterinarian.
Some of you might be wondering if you can successfully hatch an egg with more than one yolk. The answer is, not likely. Even though multi-yolked eggs are larger, there is not enough room to support the lives of two chicks.
It has been done but success is the exception.
Since we’ve address multi-yolked eggs, did you know that you can get a yolkless egg?
It’s true but again it’s rare. This happens when a piece of tissue is sloughed off the ovary and travels through the oviduct as a yolk would. I’ve never personally experienced this but I can only imagine the surprise when the egg is cracked and is yolkless.
Sandy, thank you so much for sending you pictures and sharing this rare occurrence with us.
We love to hear your feedback and your stories.