Don't feed for 2 - 3 days! After that you could throw rusty nails & hot coals in there and they will be gobbled greedily... OK, substitute collard and turnip greens for the nails and coals - or whatever other readily available reasonable fare.
You guys should check out this site:
http://www.thetortoisetable.org.uk/site/plants_19.asp
I use this still to see what my tortoise can and can't eat, and why. I really love that they include the explanations. Hope this helps everyone.