When aiming a NEWLY-TAMED horse, mule or donkey with an apple in your hand, it shows feed, right? But when you click the button, it will let you ride the horse instead. Apparently, when you feed the horse WHILE RIDING it and when you get off of it and aim at it again, the button changes to "Ride".

I'm sorry if this is confusing, comment below the problem/confusion and I'll try to reply.