Minecraft wiki entry for Horse, associated text: A player who picks up leather dropped by an adult horse receives the “Cow Tipper" achievement. This is due to the achievement being given when a player picks up any piece of leather instead of being given when one kills a cow.
A horse with a rider can be pulled by a lead, and can even be lifted into the air.
Horses eating golden foods comes from the Greek myth of Arion, a superfast horse which only ate precious minerals like gold.