Theory:Horses are from MLP
This is my theory that all the horses that are present in the show might have been the My little pony franchise
This is a cheesy thing to point out but these horses can talk just like MLP. Though we never see pegasi (multiple pegasus) in the show we can see earth ponies and unicorns and the illuminati magic stuff that goes on this show even in the intro It's been SOOO long since I watched this show but I've never seen trinket use her horn before so,the magic from MLP might have transferred to NTPK and the horses here have no magic.
Keep in mind that this is a theory!