Abnormal functioning of the ovaries and sudden contractions can be the cause of the “egg cage” phenomenon.
A farmer named Gary in Texas, USA found a particularly large egg on his farm. Suspecting something unusual inside, Gary returned to the scene where he had broken the egg and discovered another complete egg inside, according to IFL Science on September 14.
Gary said the egg was born to a 7 month old hen named Gertrude on the farm. The size of the egg is twice as big as usual. Gary has encountered many cases of chicken eggs with two yolks, but this is the first time he’s discovered that an egg has another full egg inside.
The “egg cage” is a very rare phenomenon. The reason is due to abnormal activity of the ovaries and disturbances of muscle contraction activity in chickens.
Normally, the oocytes (which later become egg yolks) are released from the ovaries and continue to complete layers in the fallopian tubes. However, due to the action of the ovaries, another oocyte is released before the birth of the first egg.