Well, it works because by some common usages, a calf is a cow.

Many people use cow to mean all bovines, even if technically not correct.

Not trying to steer this but do people really use cow to mean bull?

	▲	aaronbaugher 2 days ago \| parent [-]
		No one who knows anything about cattle does, but that leaves out a lot of people these days. Polls have found people who think chocolate milk comes from brown cows, and I've heard people say they've successfully gone "cow tipping," so there's a lot of cluelessness out there.