There seems to have been something shady going on here. I won't comment on that, but the government tracking this isn't per-se strange or unwarranted.
We should keep in mind not to trust the connotations of any translated phrase. Heck, we can barely trust the overt meaning.
That doesn't mean the government is planning to round them up and put them to work.
Besides, in the US the census collects the same kind of data, it just probably hasn't used with an agenda. Among EU members, on the other hand, data protection laws often disallow the collection of such information.
EDIT: to your point however, being married would not preclude a woman from being "breed ready" as we understand the phrase. So clearly there is some missing context needed to really understand what that column represents.