A single female is a cow
A single male is a bull
A castrated male is a steer
An unbred female is a heifer
A juvenile is a calf
All of those terms can be pluralized according to normal conventions.
There is also the collective cattle
But what I don't know, is if there is a word for a single individual of the species that can be applied regardless of sex. Something like "pig" which can be applied to any individual swine.