Knox is good stuff. It is not made of hooves, you can't make glue out of hooves. Knox is a combo of bones, connective tissue. and rawhide.
^^ you're right, i was just popping off animal body parts that we don't consume. my bad 
but you can make glue out of hooves: https://en.wikipedia.org/wiki/Hoof_glue
I was going by TBB1 page 203 where Tim Baker says,
"Two other non-sources of glue are hooves and horn. Despite common belief, dictionary definitions, encyclopedia entries, and other literature, glue cannot be made from hooves."
Now I'm stuck between Tim and Wikipedia

I'm inclined to believe Tim. I think horses feet would be an excellent source of glue because there is a lot of connective tissue, ligaments and stuff that have a lot of collagen in it, but the hoof itself is just keratin. It's not important, just interesting.