Here's a breakdown:
* Heifer: A female cow that has not yet given birth to a calf.
* Cow: A female bovine that has given birth to a calf.
* Steer: A male bovine castrated before sexual maturity.
* Bull: An intact (un-castrated) male bovine.
What is cow called when it has not produced a calf?
A cow that has not produced a calf is called a heifer.