Eggs are one of the most familiar foods to people. The large supply of eggs in the market mainly relies on modern poultry farming. We know that domestic chickens are artificially domesticated from wild chickens. However, wild birds usually only lay eggs after mating. Why can artificially raised hens, whether free-range or caged, lay eggs without mating?
To adapt to flight activities, wild birds' reproductive organs will be significantly atrophied during the non-breeding period to reduce body weight. After entering the breeding period, under the regulation of sex hormones, the reproductive system will develop rapidly and begin to lay eggs. Domestic hens, because they rarely fly and have sufficient food, do not have atrophied reproductive systems.
In the ovaries of hens, there are about 4,000 primary oocytes. When the chicks grow to sexual maturity, the reproductive system will always be in an active state. These primary oocytes will develop and mature day by day, and be discharged into the oviduct one by one. Mature primary oocytes are wrapped in yolk in the ovary, and after entering the oviduct, they are wrapped in albumen, membrane, and hard shell, eventually forming eggs and being discharged from the body.
The phenomenon of hens laying eggs is similar to the menstrual cycle of female primates, and it has nothing to do with whether they have mated with males. If a hen mates with a rooster, the sperm will combine with the primary oocytes to form a fertilized egg. Such eggs can hatch chicks. If the hen does not mate, she will lay unfertilized eggs that cannot hatch chicks. The eggs we usually eat are mostly unfertilized eggs.
Domestic hens and wild female birds, as long as their reproductive systems are in an active state, will lay eggs whether they mate with males or not. However, in nature, female birds only develop egg cells during the breeding period, which leads to the phenomenon of hens laying eggs without mating. In fact, wild birds in nature will also lay unfertilized eggs without mating, but this phenomenon is relatively rare.