I hear lots of talk about mealworms and scratch and also see it sold next to other general chicken supplies at the feed stores. For starters, what exactly is "scratch"? Is mealworms and/or scratch imperative to a laying chicken's diet? Is it just a treat? If it's just a treat, is there a reason to buy them instead of using veggie scraps? Thanks for any help on clarifying this, obviously a newbie here!