i also recently found this (posted by another member SUPER HUGE THANKS TO YOU!!) to be VERY informative.
http://www.catinfo.org/zorans_article.pdf
if you can give your cat to eat raw meaty chicken bones NOT COOKED!! along with a bit of chicken meat (to balance the phos and cal) that will help out hugely with the tartar. also getting grain products out of their food. Cats are obligate carnivores. as in NOTHING but meat. personally... i dont feed horses salmon... why would i feed my kitty grass?
-ashley