Once you have a horse, it should work pretty much like any domesticated animal. Stallions and mares can mate, and they have another quality meter in their "character sheet" that determines the maximum speed at which they can travel. Its initial setting will be at the quality of the wheat and carrots you offered to the aurochs.
Maybe even later Jorb and Loftar could expand on them with saddles and even armor, and, of course, the ability to turn them into delicious hamburgers.

Seriously guys, I want horses and so do a lot of people.