- Nutrition by Betty Lewis, RVT, Dr. A. N. Nutrition for Companion Carnivores (Note; this discussion specifically talks about dogs, but is applicable to cats as well.) Introduction Until recently zoologists classified dogs and wolves as separate species; now scientists have proclaimed that there is no differences between the two species. This change was formalized in the 1993 publication: Mammal ...home.earthlink.net/~pawsreflect/nutrition.html