Eggs

[yolande]

Are eggs unfertilised? Do chickens lay eggs whether they have a cockerel there or not? Are all chickens we eat in supermarkets female? Thanks!

[brachiopod]

1. Generally, yes.
2. If they are hens, yes.
3. Mostly, yes.

Eggs are the product of the hen's ovulation cycle, and will occur whether there is a c�ck present or not. Fertilisation of the egg occurs internally before the shell develops.

All but an extremely tiny percentage of commercial egg production will be unfertilised eggs. Occasionally, a male chick will be incorrectly sexed and, instead of ending up as 'hatchery waste' (ie. being gassed and ground up into fertiliser / animal feed within hours of hatching) - it will end up with hens in a barn / deep litter / or battery unit. In these cases, there is a chance that eggs can become fertilised.

[brachiopod]

Sorry, mis-read the last part of your question.

Chicken raised for meat ('broilers') can be of either sex.

These are a different strain from that used in egg production, having been selectively bred to gain weight quickly. (Hence why the male chicks bred from egg-laying strains, being 'useless' for meat production, are killed.)

Weight gain is so rapid in modern broiler strains, that birds are ready for slaughter at around 42-45 days - (since sexual maturity is not reached until around 18 weeks, it ensures egg-laying in broiler flocks is not a problem.)

Broiler flocks can be mixed or single-sexed, so the chickens you see in the supermarket can be of either sex.

[McNoodle]

brachiopod - if the shell occurs as a result of fertilisation, how can it be, as you say, that eggs we eat our 'generally' unfertilised?

[drchasuble]

The shell develops at a later stage whether the egg has been fertilised or not.

The egg is just a sort of yolk around which the shell grows.

[drchasuble]

http://www.enchantedlearning.com/subjects/bird s/info/chicken/egg.shtml

[brachiopod]

Sorry, just to clarify;

Fertilisation (if it happens at all) occurs way before the shell is formed, when the egg is little more than the ovum cell and a sac of yolk, known as an oocyte.

As the oocyte passes down the hen's reproductive system, the albumen, egg membrane and finally the shell are formed around it.

This process will proceed whether the oocyte was initially fertilised or not, forming the shelled 'egg' we are familiar with.

It is not dependent on fertilisation.

[brachiopod]

Sorry, drchasuble, you posts weren't there when I started typing!