Please forgive me for this post's title.
|On the left is an example of one of Petunia's regular eggs. On the right is the mammoth that she laid last week.|
We bought our hens as week-old chicks in February 2010 (surprisingly, every chick we bought turned out to be female), so they just started laying eggs in July. Hens under the age of 1 year are technically called "pullets", and they start off their egg-laying careers by producing small pullet eggs. Our girls were quite disconcerted by their changing bodies, and their first egg-laying endeavors started with lots of pacing and squawking. Understandably so.
That was nothing in comparison with the squawking that poor Petunia did when she laid the monstrosity pictured above. She went from laying pullet eggs to laying a gigantic double-yolker in one day. It was fortunately an anomaly, and her eggs have since returned to their normal size.
What's the deal with double-yolks? According to poultryhelp.com, they appear "when ovulation occurs too rapidly" and are often laid by pullets who don't yet have a properly synchronized laying cycle. Here's a more detailed answer:
When an egg starts its journey inside the hen, the first thing formed is the ovum in the hen's ovary. This grows and the colour changes from pale grey to the yellow we know as the yolk colour.
Once it reaches full size, the yolk sac breaks away (ovulation) and begins a journey down the oviduct where the egg white (albumen) and the shell form around it. The process from ovulation to egg laying takes around 24-26 hours.
Normally, the next ovulation is triggered by the hen laying the egg but occasionally things go wrong and two yolks are released at the same time to travel down the oviduct together, being surrounded by one shell and giving us the double yolker.
Much to the chicken's horror.