How Does a Chicken Produce an Egg?

The natural process by which a chicken lays an egg is not often thought of. Consumers go to the store and pick up a dozen eggs without thinking where they came from or how they may have been produced by the animal. The life cycle of a hen and her ova is a long one but it can be interrupted by the needs of the farm and of the farmer. Regardless, the way that an ova travels to become an egg is a fascinating journey.

  1. Young Hens

    • A hen is born with all of the ova that she will have in her lifetime. This means that at birth she has a predetermined maximum of how many eggs she will lay in her lifetime. This number varies from 1000 to 4000 eggs. This does not mean that all will ova will become eggs and be laid. A healthy and good laying hen has a soft underbelly, wide pubic bones and a moist vent. The vent is the tract like a vagina that carries the developing eggs to the surface.

    Laying Hens

    • A hen will begin laying eggs at around four months old. This is a natural and independent process for the hen and she does require a rooster to lay eggs. The ova transform into eggs and as they travel down a 2-foot tube called the oviduct they grow hard egg shells around them. The first eggs that a hen lays is small and inedible and she will lay only one egg every three or four days. By the time she is around six months old the eggs will be of normal size and she will lay two eggs every few days. This is a continual act. The ovas are constantly making their way down the oviduct to the surface.

    Fertlized Eggs

    • Farms that use their chickens primarily for egg laying keep the hens away from the roosters because a fertilized egg is of less use to them. A small group of roosters are housed for the purpose of sexually fertilizing eggs. This is done to replenish the stock of chickens. As a result fertilized eggs that are cared for and allowed to become chicks are observed to see if the offspring is male or female. Many farms destroy the male chicks, sell them or use them for food.

    Production Cycle

    • A healthy hen lays 20 dozen eggs her first year. At 18 months the hen has her first molt and her feathers fall off and gradually grow back. This process takes about three months. Because of the energy involved the hen does not lay any eggs during molting. After the first molt she lays about 25 percent fewer and still fewer with each molt. This is why most laying hens are destroyed when they are over two years old and they never get the chance to lay all of their ova. The cost of feeding a lower producing hen is too great and she is replaced by a new chick.