The Life Cycle of the Chicken
Lets look at the different parts of an egg.
Picture of TS egg with its parts labelled
Think of the different parts as being layers that are added one at a time from the inside out. The egg starts with a egg cell. This is the small, rather tough white you see on the egg. As a yolk passes thought the oviduct, or egg-laying tube, four separate layers are added. All of these parts are kept in shape by two very thin layers of transparent membranes "skin", and finally the shell - is added in turn. And just a few hours before being laid, the egg receives its pigmentation. The pigments are produced in the chicken's body. And because each egg is colored separately, there is a lot of variation even in eggs laid by the same chicken. Each chicken can lay eggs that haven’t been fertilized. But these unfertilized eggs will never develop an amnion, allantois, chorion, or embryo. Most of the chicken eggs you buy in the grocery store are unfertilized eggs.
Lets look at the hen.
Picture of a hen with egg in the body
Before it can produce a baby chick, and egg must be fertile. A hen can lay eggs all her life without laying a fertile egg. In order to produce a fertile egg, a hen must have a husband. Most the eggs you buy in the store are unfertile, and would never be a chick.Picture of the developing embryo and developing chicken
The egg cell in the fertile egg is the part that becomes the baby. Before the egg is hatched, the baby is called an "embryo"
The embryo must have food while it is growing. It gets its nourishment from the yolk of the egg. That is why the egg cell is always attached to the side of the yolk. A day or two before the chick hatches it pulls what is left of the yolk into it’s abdomen through its umbilical cord. To use as a food source after it hatches.
The egg white is a cradle for the growing embryo. If the egg gets bumped, or moved to suddenly, the soft white around the embryo comes between it and the shell and cushions the shock.
The shell protects them all from being hurt or damaged.
Take a magnifying lens and look at the shell, do you see those little holes? The embryo breathes through these holes. The shell, that looks as though it were solid, is actually porous. That is, there are thousands of tiny holes in it, so small that it is impossible to see them. At the large end of the egg is an air pocket, filled with oxygen.
A fertile egg is so delicate that it can be ruined by small mistakes. Sometimes a perfectly good egg won’t hatch because it has been turned wrong end up, or shaken.
Mother knows best.
A mother hen reaches underneath her body and turns her eggs frequently with her beak. This is because the egg yolk tends to float toward the shell. When the egg lies too long in one position, the white separates and allows the yolk to float through, forcing the egg cell against the shell and killing it. The hen avoids this by changing the position of the eggs. She keep them warm by spreading her feathers over them. She is very careful with them and won’t let anyone else touch her eggs.
When using an incubator at home, eggs must be turned regularly to prevent the yolk from settling to one side and to exercise the embryo. When you turn the egg, the embryo gets it exercise by turning in the shell until its head is upright. Eggs should be turned at least twice a day. At a hatchery they have large incubators which turn the trays which the eggs are in. 3 days before the eggs are to hatch they stop turning them. The temperature should be kept at 100degree. If you want to hatch chicks at home you can purchase a small incubator and eggs from a school supply store. And if everything goes right in 21 days you will have new chicks.
Did you know that chicks and chickens do not have teeth. They use their gizzard to make their food smaller. This organ, located just before their stomach grinds the food into smaller pieces for them. But they need small rocks called grit to help them do this. A chick doesn't need grit till they are about 7 days old. Then it is sprinkled on their food daily.