Yep. I don't believe in giving "vitamin supplements" for any reason other than medical ones (I give Visa Nutri-Cal because it is high calorie amd helps her keep on weight). Other than vitamins though, I see no reason why you can't supplement the food with other things.

I give Visa seal and fish oil. I also give her "Wonder Pet" which is a mixture of shark cartilage, glucosamine, and chondroitin. I give her Mega-Min which is a liquid variety of herbs that help to prevent a number of problems and boost the immune system. She gets kelp and alfalpha and occasionally I give her a mixture of powdered herbs from Bone Appetit. She always gets her Biological Vet Skin&Coat and Sport.