What is an egg ? and what the process of formation of an egg in poultry ?
In this article, I will explain what an egg is and how formation of an egg takes place in the poultry. The egg start with the process of an ovulation from ovary and goes toward the other parts of reproductive tracts where different secretion occurs and finally the formation of an egg occurs.
Definition of egg:-
The oval or sometime round body laid by domestic poultry birds. It consists of a yolk, usually surrounded by the "white" which is called as albumen, and inclosed in a shell which provides strong membrane surrounding the albumin, which is made up of calcium carbonate.
Formation of the egg:
The egg consists of the true egg or reproductive cell, that is, the yolk with its germinal disc and the surrounding envelops of albumin, shell membranes, and the shell. The yolk is formed in the ovary but the balance of process occurs in the oviduct.
Ovulation:
When the yolk or ovum reaches maturity the follicle ruptures along the stigma and yolk released is engulfed by the infundibulum by its contractions. Fertilization takes place in the infundibulum if the live sperm are absent the eggs spends about 15 minutes here.
1.Secretion of dense white:
The yolk then passes in to the magnum or the chalaziferous region of the oviduct which secretes the thick white. The yolk spends about 3 hours in the magnum.
2.Formation of shell membranes:
When yolk passes through isthmus inner and outer shell membranes are formed and some water and salts also added. The shell membranes remain loose until they obtain full quota of albumin in the uterus. The egg remains for about ¼ hours here.
3.Formation of chalaze:
Two whitish cord known as chalaze which extend out from the yolk towards the ends of the egg or obviously formed from the material secreted in the magnum. However, it is not visible until after the egg has enter the uterus. The chalaze are formed due to change in the colloidal structure of the layer of the white next to yolk and partly as result of rotation of white around the yolk while egg is in the uterus.
4.Formation of shell and secretion of thin white:
As the egg enters the uterus the shell is deposited. A considerable amount of shell material is deposited on the membranes before the thin white is added to the egg by osmosis through the two shell membranes which swell up to make it firm . The rate of shell deposition is relatively law, during the first three hours, than increases rapidly until about the fifth hour, after which a constant rate is maintained. Eggs spend about 18-20 hours in the uterus.
5.Laying of egg:
Just before oviposition the cuticle or bloom is probably secreted in the vagina and the egg turns around horizontally by an angle of 180º just prior to being laid, so the egg is laid with its broad end first.