How Turkeys Breed
Slate runs a piece on how farmers produce so many birds for Thanksgiving:
With a little help from their human friends. The vast majority of turkeys sold in the United States are of the white broad-breasted variety. These birds have been bred to produce as much white breast meat as possible, resulting in males so large and unwieldy that they can't properly mount the females. Toms therefore have to be manually stimulated and "milked" for their semen, which is then inserted into a hen using a syringe.