Monday, 17 October 2011

Things about eggs..

Fact number 1.. Hens do NOT need a cockerel to lay eggs, unless you want chicks..they don't in fact have anything to do with egg laying...I get asked this all of the time, so here is some reading material for all of you who are interested in exactly how things work eggwise...

Egg Production

It takes different times for the egg to pass through the different areas of the oviduct (egg tube), the addition of the shell taking the longest time:
  • 15 minutes in the infundibulum (fertilised here if cockerel available plus chalazae added)
  • 3 hours in the magnum to add albumen (white of egg)
  • 1.5 hours in the isthmus to add shell membrane
  • 20 hours in the uterus/shell gland for shell deposition plus pigment
  • 1 minute in the vagina which is extruded out past the vent to avoid the faeces

This is an egg I cracked open to find it had been fertilised and was in fact alive .....

An egg takes a total of 25 hours to lay ,which is why the hens do not lay every day, they then ovulate again about 30 minutes after laying.
Brown eggs have pigment placed on the outside of the shell which can scratch of wash off  unless you are one of those gorgeous blue/green eggs from an Araucana which has pigment all the way through.
The other thing is that egg shells are porous so they must be washed with water that is warmer than the egg (with a disinfectant like Virkon or an egg wash)  so that the shell membrane expands and blocks the pores, because if the water is cooler the membrane shrinks and will draw in any bacteria on the shell.

If the eggs are needed to be fertile, there are semen storage glands in the oviduct so the cockerel does not need to be with the hens every day, important if the hens are exhibited so that their feathers do not get damaged. If another breed cockerel has been used and a different cockerel is wanting to be used (for instance, to change to a pure breed) you will need to wait 2 weeks for the eggs to be true to the new cockerel, due to the semen storage capacity

.The composition of an egg is shown.. 

This is important as it is how a fresh egg is determined. The airspace is very small in a new laid egg and gets progressively larger as the egg loses moisture through the porous shell. When a fresh egg is cracked onto a plate, the thin white and the thick white are easily distinguished and the yolk sits in a defined dome on top of the white. The chalazae can be seen. A not-fresh egg will appear to have only one type of white, no chalazae and will be flat when viewed from the side. Sometimes there may be a small brown mark in the white – this is a tiny amount of blood (known as a meat spot) and is not harmful, it just doesn’t look nice. Commercial eggs are candled (looked at in a dark room with a bright torch held to the egg) to remove any with meat spots. Fertile eggs are candled to check on the development of the embryo. The colour of the yolk depends on feeding and commercial feed has additives to enhance yolk colour. Carotenoids in green plants are the basis of yolk colour, so outdoor birds usually have darker yolks in the summer and paler in the winter.

The laying process is hormonal, and very much influenced by light levels, which is why you can hear me moaning when I have so few eggs during the Winter, for so many birds.. If I had Ducks I might have a good deal more eggs as they are less influenced by the light and light breeds do lay in the darker months.

What a cock! 

No comments:

Post a Comment