How are eggs made?

How long does it take for a hen to make an egg? 

The eggs develop from ovulation to egg laying (oviposition) in just over 24 hours. The ovary contains all of the ova for the lifetime of lay and birds come to maturity from around 20 weeks of age, depending on their breed, rearing and the time of year. Birds mature more quickly with longer daylength (Spring). 

Diagram of a hen’s reproductive tract

Does breed make a difference? 

Different breeds lay at different rates. A typical brown hybrid layer will produce at peak production an egg on 9 out of every 10 days. Whereas traditional breeds often produce eggs at lower rates. 

Diagram showing the parts of a hen’s egg

What is the egg yolk? 

The yolk you see inside an egg is actually the ova the bird ovulates. The active ovary displays a phenomenon described as follicular hierarchy, where there is ongoing development of several maturing follicles, each at slightly different stages, ranging in colour and size up to an ova just prior to ovulation, reaching approximately 40mm diameter with vivid yellow appearance (which becomes the yolk). A typical brown hybrid layer will have approximately 12-14 yellow follicles of various sizes visible on the ovary at any one time, essentially one for each egg. 

The yellow yolk is designed to sustain the newly hatched chick. It mainly consisting of a lipoprotein complex including antibodies, high cholesterol for energy along with a high Vitamin A & D content. 

What is the egg white? 

Egg whites are predominantly multi layered complex proteins in a water matrix laid onto a proteo-carbohydrate sac then envelopes the yolk. The yolk is suspended in the albumen by polar cords of twisted albumen, like strong cords. The egg whites are laid down during the first four hours post ovulation after which the next 20-hours is required for egg shell formation. 

What is an egg shell? 

The shell consists of a calcium carbonate deposit onto an organic shell membrane, resulting in the hard, protective outer shell.