I don't live day to day in this part of the business, but in the commercial egg world we need 1 rooster for every 8 - 12 hens to "get the job done". More than that and the roosters will compete with each other for dominance. Less than that and the fertilization rate is not good. For every 100 eggs that come from the parent facility we will end up with 43 female chicks for egg production after 22 days of incubation and hatching. It is also very breed specific as to how often it happens, but not uncommon for the female parents to get upset with the roosters and kill them. The work of the genetics companies that supply commercial producers is fascinating and is rather intricate. They keep "pure" lines that are selected for general performance and can be traced all the way back to jungle fowl. They select from the best performers from a myriad of selectable traits and those become the great great grandparents. From those very few birds they create great grandparent, grand parent, and parent flocks and each step also multiplies the size of the flock to get to commercial production levels which commonly see the largest hatcheries set 1 million eggs per week. The commercial egg laying industry needs about 250,000,000 day old female chicks/year to keep production going for US needs. Put another way(and I think I did the math right), there are approximately 250,000 commercial roosters in the US getting the work done so that all of us can enjoy the approximately 280 eggs/capita each year we consume. It is substantially larger number for the meat bird industry, and the turkey industry is quite different as they use artificial insemination.
