I don't feel that my cats need any extra vitamins. Too many of some vitamins can be harmful, so I stick with feeding higher quality foods and rotating them. That way, they get their nutrition from food alone, which is better absorbed, and from different meat sources to provide the most balance in their diets. Odo gets a rotation of several canned foods, including three flavors of Natural Balance, Innova, Innova EVO, occasionally some Merrick's and Evanger's when I can find it. Willow, who won't eat a full meal of canned food, gets California Natural dry and some canned snacks on occasion (usually the fishy stuff, since that's what she likes to eat). She also takes a few bites of Odo's food on occasion.