'I've Never Seen Anything Like It': Massive Chicken Egg With A Second Egg Inside Is A 'Freak Of Nature'

A hen farm in Queensland, Australia, has made headlines after an employee found an extraordinary egg in one of its free-range sheds.

At 176 grams, the egg is three times bigger than a standard egg—a remarkable find in itself. However, when staff cracked it open expecting to see two or three yolks—a relatively common occurrence in larger eggs—they were shocked to find another perfectly formed, regular-sized egg encased within.

“It’s very rare to get such a big egg, and all of a sudden there was another whole egg inside,” Scott Stockman, the owner of Stockman’s Eggs, told 9news.com.au. “We were all quite shocked. The nutrition must have been spot on to get the egg fully formed.”

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The farm’s poultry vet described this extremely rare phenomenon as a “freak of nature”, a spokesman for the company told Newsweek. In addition, a number of experts we contacted, including Anders Miki Bojesen, a professor of Preventive Veterinary Microbiology at the University of Copenhagen, said they had “never seen anything like it” before.

Gaynor Davies, head of operations at the British Hen Welfare Trust added: "Speaking as a veterinary nurse who has spent nine years working with hens at the British Hen Welfare Trust, it is very rare to come across an egg inside an egg, and certainly one of this size.”

So, what could have happened to produce this strange phenomenon?

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To answer this, it is first important to understand how eggs are produced normally. Hens have one functional ovary—the left one—where the yolk matures. This yolk then travels from the ovary down into the oviduct—the tube through which the egg passes. It is here that the egg white is generated over a period of three or four hours. Finally, the egg passes into the shell gland where the shell is formed—a process that usually takes about a day.

The egg’s journey is powered by a series of wave-like muscle contractions, known as peristalsis, which squeeze it along its journey through the body, in a similar manner to how you would squeeze the last bits of toothpaste out of the tube.

Being such a rare occurrence, explanations for how the ‘double egg’ formed differ due to the fact that it is not well studied. One hypothesis suggests that the process of peristalsis may have been interrupted in some way.

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“If there is some sort of hiccup—the bird takes a fright for example—the muscles can go into a spasm or reverse and the formed egg can start moving backwards up the oviduct again,” said Stephen A. Lister, a European specialist in Poultry Veterinary Science.

“The oviduct recognizes this as a slightly larger yolk and starts laying down more egg white, a new bigger shell membrane and finally a big shell totally encasing the first egg.”

Davies, on the other hand, offers a slightly different explanation: “If an egg stays in the shell gland for too long, the next ovulation will take place, but before the previous egg is laid.”

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“When a second egg is released this can cause a contraction, which essentially 'pushes' the first egg back up into the oviduct,” Davies said. “The two eggs then travel back down into the shell gland together and a shell is formed over them both, creating a supersized egg. This process is known as a  counter-peristalsis contraction, which is generally more likely to happen in either hens reaching end of lay or older birds.”

The farm said it would be impossible to identify which of its 60,000 hens had laid the special egg, but what is clear is that it would have been a very uncomfortable experience.

“I don’t envy the poor hen who laid it!” Davies added.