Wait till you get into the other agricultural practices like raising sheep for wool or selecting your herd bulls.

Sheep get castrated, ears notched and tail docked. Then they get set out to pasture.

A bull is selected to be your herd bull and any cows either get milked as you described or pastured to be mama cows for building a herd. Any bull calves either get sold off to be someone else's herd bulls if the genetics are good enough or they get castrated, notched ears and in at least one herd I have seen, their tails are docked.

As the old ag teacher in high school explained, you castrate them to keep their minds off of the ass and put 'em on the grass.