Thank you for responding to all this!

Yep, it can be a little overwhelming to make sure they are getting what they need.
So, chicken and turkey neck/back bones aren't worth feeding? Are the wings any better?
I am reading different things about pork - some for and some against. I know pork chops are not good - what other kind of pork would be good for them? The riblets are ok from what I've read, but those bones are pretty small - they're still ok?
Thanks for your info.. I'm sure I'll have more questions.