Learn English – n adjective for deer-like

There are three terms used for this purpose. Here's a description of all three from Wikipedia.

1. Boar or hog, male pig of breeding age.
2. Barrow, male pig castrated before puberty.
3. Stag, male pig castrated later in life (an older boar after castration).

From my experience working on a cattle farm, it gets too pedantic to keep on saying "cattle," so we just said "cow" when the context made it fairly obvious that there was no specific reference to gender. However, one tends to avoid the use of that word by simply using the correct gender form, as in "bull" or "cow."