Development & breeding of chicks

The eggs we eat come from hens. Very few are laid by ducks. Chickens, turkeys, ducks and geese provide our poultry meat. Most of the poultry meat originates from chicken. Some 100 million broilers are grown annually in Northern Ireland.

Traditionally the live poultry on farms were dual purpose breeds used for both meat and egg production. In recent years separate strains of birds have been bred for egg production and for chicken meat production (broilers). Whether birds are kept to produce eggs or meat they start life as an egg.

Chickens provide nearly all the eggs and most of the poultry we eat. Chickens bred for eggs originate from light breeds oiliest those bred for meat are heavy. No matter whether they are light or heavy breeds they start life as an egg!

A mother chicken is called a hen. A father chicken is called a rooster or cockerel. A baby chicken is called a chick.

Eggs collected from flocks with roosters produce the fertile eggs for incubation. Infertile eggs from flocks without roosters are used for eating.

Information:

Shell

The shell is predominately formed of calcium carbonate. It protects the egg contents from contamination, provides the minerals to form the bones of the developing chick and allows the exchange of oxygen and Carbon dioxide. Remember it is much easier to get from inside to outside of the egg than it is to get from the outside to the inside!

White

The albuminous mass of the egg acts as an additional source of nutrition for the developing chick particularly water soluble vitamins.

Yolk

The yolk is high in fat and provides energy and fat soluble vitamins for the developing chick.

Air Cell

The egg is laid at 40 degrees Centigrade the body temperature of the hen. The air cell is formed on contraction of the egg contents on cooling immediately after laying. It forms between the two shell membranes at the 'blunt' end of the egg. It enlarges during incubation as a result of evaporation of moisture from the egg.

Chalazae

The chalazae are mucilagenous structures, one of the functions of which is to keep the yolk positioned centrally within the egg and thereby help prevent the embryo sticking to the shell membrane early in incubation. The chalazae at the pointed end of the egg is stronger than that at the broader end, so that eggs should be stored pointed end down. The yolk contains fat and tends to float. The chalazae from the pointed end anchors the yolk.