“Cow” includes bulls, heifers and steer.
In the usage I'm familiar with, "cow" specifically means a female who has given birth. As opposed to heifers, who haven't. The general term for any member of the species would be cattle (both singular and plural). You might use "cows" to more generally mean any female cattle, but using it to include males of the species, too, would be understood as humorous.
EDIT: Even googling "beef cows" provides a wealth of contradictions to your statement.