Yes, it does mean only females:
1.a fully grown female animal of a domesticated breed of ox, used as a source of milk or beef: See cattle.
"a dairy cow"
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BUT, in informal language, we often refer to any cattle, male or female, as cows. It is not proper English, but we use it to mean just "cattle". It would be best to say, "He raises cattle in the country" if we mean male and female, bulls and cows.
NOTE: A cow is also a mature female of elephant, moose, and a few other mammals, too, not just cattle.