I added horses to way too many households, lol. A few houses where it feels wrong for the sims living there having a horse, sometimes got an empty stable (used to park their bicycles?) to indicate that the former owner had a horse :)
I put together an overview showing (me) what horse breeds would be more likely in certain worlds, based on real life and climate etc, although I learned these borders are no longer as true as before.
You can see the overview here.
I also keep an online
household index here, and horses are naturally included as household members (click their icon to see what breed they are) :)
