After reading on the World Health Organization's warning that processed meat is carcinogenic (in humans), even in small daily doses, I went on to investigate if this finding also applies to pets, and found this study: "Twenty-five commercial pet foods were analyzed for mutagenicactivity using the Ames/Salmonella test with strain TA98 and added metabolic activation. All but one gave a positive mutagenic response. Fourteen of these samples were analyzed for heterocyclicaminemutagens/carcinogens and all but one contained 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 10 of 14 contained 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) as analyzed by HPLC and confirmed by photodiode array peak matching. From these findings it is hypothesized that there is a connection between dietary heterocyclicamines and cancer in animals consuming these foods." http://www.ncbi.nlm.nih.gov/pubmed/?term=Mark+G.+Knize+MG,+Salmon+CP,+Felton+JS.+Mutagenic+activity+and+heterocyclic+amine++carcinogens+in+commercial+pet+foods.+Mutation+Research.+2003;539:195–201 Unfortunately I can't access the full paper, but I presume they tested with dogs and cats. If you find anything else about this topic I'd be glad to read it, I'm considering switching my cat's diet to a raw diet.