Fermenting feed: How big are holes in bucket??

[mphsgal]

I don't have time to read all of the FF thread right now (I've read the first 30 or so pages), plus the other threads, plus a search isn't telling me what I need to know, LOL. So forgive, please, if asked & answered.

1. Using the double-5 gal. bucket method, how big are the holes in the top bucket?
2. Do I need to switch to different-sized holes when I switch from chick crumbles to broiler feed?

25 babies coming this week. Answers GREATLY appreciated, LOL!
L.