Schnauzer's Foul Eating Habits

Our 7-month old mini schnauzer keeps his muzzle to the ground when going for a walk and loves to pick up anything and everything into his mouth...deer poop, insects, stink bugs, etc.
Is this something they grow out of? We've tried distracting him with treats along the way, but he is so sneaky that many times it's too late--the thing was already swallowed!

Can anyone help?