A sense of smell is one of the most useful things that a horse has, besides eyesight and instinct.
This is Ace getting to know her foal. Allowing the little one to breathe on her nose gives both of them the information needed to create a bond.
If you want to make friends with a horse, put your nose close to its nose and inhale the breath the horse breathes out.
The air you then release is enough like horse breath that the horse accepts you as a friend.
Believe it or not!