Old OLD argument... Hatching females..

[lemurchaser]

So in chickens the hen is ZW and the rooster is ZZ (instead of XX or XY in humans). So the hen determines the sex of the offspring, by producing an egg with a Z or W gene. That Z or W is fertilized by a Z from the rooster, and the rooster can only "donate" Z genes. So a hen determines the sex genetically.

While looking that up I found this article saying that organically raised chickens have different gene expression than factory farmed ones. Interesting!
http://www.popsci.com/science/artic...-how-chickens-process-organic-vs-regular-feed