If one visits pro raw pet diet websites or reads the posts by raw diet advocates on forums and the like, a number of arguments for the superiority of raw diets for cats (and dogs) are repeated over and over. While some of these arguments superficially seem reasonable, a more critical consideration reveals that they are at best unproven and at worst false. None at all are definitively true. None!
Here are the most common myths put forth by raw cat food advocates:
Let's now consider each of these arguments, and see why they simply are not true:
There is no doubt that the wild ancestors of domestic cats, African Wildcats, eat raw meat diets (i.e., the prey they catch). However, for this to imply that a raw meat diet is best for domestic cats would require two additional premises be true: (1) domestic cats are essentially identical in physiology to African Wildcats, and (2) raw meat is the best diet for African Wildcats.
So are domestic cats essentially identical in physiology to African Wildcats? No! In fact, they differ in a manner that is extremely significant to the diet debate: domestics cats intestine length (and width) is different from that of wild cats. This fact was noted by Charles Darwin in his book The Variation of Animals and Plants Under Domestication (1890):
A much more important difference, according to Daubenton, is that the intestines of domestic cats are wider, and a third longer than in wild cats of the same size; and this apparently has been by their less strictly carnivorous diet.Cat genetics researchers Driscoll, et. al., in The Evolution of House Cats (Scientific American) and From wild animals to domestic pets, an evolutionary view of domestication (PNAS), say:
The domestic cat varies little morphologically from the wildcat body plan, although, as Darwin noted, domestic cats have longer intestines than wildcats, a trait he attributed to a “less strictly carnivorous diet” as a result of feeding on kitchen scraps. So an argument can be made that cat domestication is <200 years old and may yet be incomplete.Researchers studying the Scottish Wildcat make even more extreme claims:
Dr Hetherington points out that there are also a number of significant internal differences between domestic and Wildcats. “For example,” he said, “Wildcats have a gut length half that of a domestic cat. The cranial capacity, the size of the brain case, is much larger in a Wildcat and there are also significant differences in the limb bones.[http://www.usscots.com/article/detail/Scottish-Wildcat/
So, domestic cats have evolved as a result of eating food supplied by humans and/or available around humans, during the 10,000 years they have been in human company. They no longer have the same digestive systems as their wild ancestors. That this fact is nowhere to be found on any pro raw website we have found demonstrates just how incompetent--or downright deceitful--most raw cat diet advocates are. This indisputable fact of differing intestine length by itself invalidates the raw "evolution argument" that can be found on virtually 100% of pro raw websites. Since domestic cats are not the same physiologically as their wild ancestors, it is unclear whether what is best for domestic cats to eat should be exactly what is best for their wild ancestors to eat.
But wait, we said there were two assumptions needed for the evolution argument to be valid, and we have debunked only one so far. Let's now consider what evidence there is that raw food is the best diet for Wildcats:
To be able to conclude that evolution shows that a raw meat diet is "better" than a cooked meat diet for Wildcats because that is what they evolved to eat, a cooked meat diet would have had to have been an available option while Wildcats were evolving. Of course, it was not. Wildcats--like every single non-human animal--have no choice but to eat raw diets because they lack the intellectual and physical capabilities to control fire and cook their food. While one may be justified in concluding that evolution shows that almost exclusively meat diets are better for Wildcats than those including the plants that were available to them, evolution had no chance to "consider" cooked diets for Wildcats, so no conclusions about the relative merits of cooked vs. raw meat diets can be drawn from Wildcat evolution.
What about from domestic cat evolution? One might argue that Wildcats did have a chance to get access to cooked meat: by hanging around the one animal that is able to cook its food, us! And some Wildcats did do exactly that. Most cat history researchers (e.g., Driscoll, et. al. in articles mentioned earlier) argue that cats self domesticated rather than being domesticated by humans. While this might have given them access to rodents around grain stores and the like, it also gave them access to the remnants of human meals, which were largely cooked (and we know they ate human food because their intestines adapted over time). So how did this self domestication work out for the subset of African Wildcats that took this path? Quite well, as they are now by far the most numerous type of Felid (cat) in the world. Thus, we might argue that if Wildcat evolution tells us anything at all about raw vs. cooked foods, it is that a cooked diet offers advantages. (This paragraph is somewhat tongue-in-cheek, as there were obviously other advantages for Wildcats from living with humans than access to our cooked food--though because eating our food caused their intestines to adapt, it seems likely that this was not an insignificant factor.)
Human evolution provides yet another lesson in why the lack of access to a cooked diet means that the evolution of Wildcats to eat raw is meaningless for deciding between raw and cooked for domestic cats. What did our ancestors eat prior to learning to control fire and cook food? That's right, raw meats and other foods--because just as with Wildcats and all other animals, they had no alternative. According to the "logic" of the pro raw "evolution argument," we humans should all still be eating raw meat today: when cooking became possible, we had evolved to eat raw, so that should have been the best for us. Of course what actually happened was that the humans that ate cooked foods became dominant, and from what we have read, every human culture in the world cooks some of its food. In fact, it has been argued by some resarchers that it was the invention of cooking that made us the dominant animal that we are today (E.g., "Catching Fire: How Cooking Made Us Human," by Richard Wrangham, see review here: http://www.nytimes.com/2009/05/27/books/27garn.html?pagewanted=all ). So our own evolution provides yet another reason why the raw "evolution argument" is invalid.
In fact, there are other important reasons to be cautious about applying supposed lessons from Wildcat evolution to our modern domestic cats. The average lifespan for African Wildcats living in the wild is significantly less than their potential lifespan, and significantly less than that of modern (non-feral) domestic cats. Estimates vary, but most sources state African Wildcats have an expected lifespan of about 7 years in the wild (though they can live to 15 years in captivity). Because of this, there likely was little if any evolutionary pressure to select a diet that optimized health in old age. The "best" diet for an African Wildcat that must hunt for all its food and will live only 7 years, may not be the best diet for domestic cats that live in less physically active environments and that we want to live for 15 years or more. This is similar to our own situation: an appropriate diet for a human in the 1800's that did manual labor and would live to be only 50 or so is not the best diet for a sedentary office worker of today who wants to live to be 80.
Finally, while African Wildcats do eat a raw diet, they also eat particular raw diets, and those diets are quite different from what is in the raw diets commonly fed to domestic cats. African Wildcats consume mainly small rodents such as mice, rats and gerbils, but also insects, birds and small reptiles. While rabbit may be fairly similar to this diet, domesticated poultry and beef certainly are not. The superiority of any "raw meat" diet is definitely not what evolution teaches us.
So let's be clear on what have we shown and why it was important to do this. Virtually every pro raw website will include an argument in support of raw diets for cats along the lines of: "raw meat is what they evolved to eat so obviously a raw meat diet is best for cats." This is generally put forth as one of the primary arguments in support of the pro raw diet position. What we have shown, however, is that this is an invalid argument because it implicitly relies on premises that are false. Thus, the "evolution argument" does not provide logically valid support for raw diets being best for cats. It may be that they are best or it may be that they are not. However even if they are best, the "evolution argument" will have had nothing to do with proving this. At best we might excuse someone who makes this argument as simply not having fully thought it through, but at worst, anyone who uses the "evolution argument" to support raw cat diets demonstrates a profound lack of knowledge about logic, cat physiology, and evolution.
The feeding experiments run by a physician, Dr. Francis Pottenger, during the 1930's are another staple of pro raw advocates and their websites. The Wikipedia page summarizes very briefly the experiments that were run and their basic outcomes. From the perspective of raw advocates, what is so important about these studies is that the cats fed a raw meat diet were healthier than those fed the cooked meat diet. Then there is the veneer of science to these experiments, with this basically the only "science" that can be cited in support of the superiority of raw diets.
For cat owners considering what is best to feed their cats in the twenty-first century, however, Pottenger's study is irrelevant. First, the cooked diet Pottenger used has nothing whatsoever to do with modern commercial cat food--unless you believe that cooking of meat automatically turns it into some kind of "poinson" for cats. Of course, feeding studies with modern commercial diets show that this is not true, just as they show that the health results Pottenger saw with his cooked diet do not occur. Second, even if Pottenger proved that some raw diet was better than some cooked meat diet, so what? It is easy to prove that nutritionally incomplete raw diets can kill cats in mere months (UC Davis study). The nutritional needs of cats were almost completely unknown in the 1930's, and the nutritional completeness of any of Pottenger's diets are largely unknown (since they varied as he used whatever meat scraps were cheaply available and were not assayed--since this is the 1930's were are talking about).
As for Pottenger's studies being "scientific," even that is not correct. It is extremely unlikely this work could be published in a reputable journal today, as the diets were poorly controlled, of completely unknown nutritional composition, the cats were donated from various sources so had variable/unknown health backgrounds, and so forth. While Pottenger's experiments may have been fine for his purposes and for the 1930's, they do not come close to meeting the scientific standards of today. So one of the main reasons pro raw advocates cite a 70 year old study (because it is "scientific") is not really true; it is only very poor science.
Probably the best debunking of Pottenger can be found at the Beyond Vegetarianism website: Pottenger's Cats experiment. While this website is primarily concerned with human diets, the above linked page clearly lays out the reasons why Pottenger's study is of no value now for making decisions about human diets or cat diets.
About the only thing Pottenger's study might be useful for is as a cautionary tale for people contemplating making their own cat diets--particularly if they plan to cook the food. For pet owners looking for information to help them choose between modern commercial diets and raw diets, though, it is utterly worthless. The fact that it invariably features prominently in the arguments of pro raw pet diet advocates once again demonstrates how ill informed and misleading their advice is!
The precise claims made vary somewhat among sites and people--and they tend to be a moving target as one repeatedly shows each particular claim to be false--but the basic idea is that there is no need to be concerned about any pathogens that may be in the uncooked meat that you feed your cat, as it won't (or probably won't) make them sick (or at least it won't kill them)--at least not if they are "healthy" adult cats.
While it is possible to find discussion of some experiments done 30-40 years ago showing that cats could tolerate higher numbers of salmonella bacteria than humans before becoming clinically ill, most of the time this conjecture about cats being relatively immune to pathogens is supported by nothing more than descriptions of features of the cat's digestive system that aim to protect them from pathogens in their food. This can sound very impressive to somebody that knows nothing about the physiology of mammals. "Cats have highly acidic hydrochloric acid in their stomachs, with a ph of 1, which kills off any bacteria they ingest." Wow, hydrochloric acid, that sure sounds like it would kill any bacteria. Oh, yeah, except human gastric acid is hydrchloric acid: "The pH of gastric acid is 1.35 to 3.5  in the human stomach lumen,.... In addition, many microorganisms have their growth inhibited by such an acidic environment, which is helpful to prevent infection." [Wikipedia]. So humans (and all other mammals!) employ the exact same mechanisms. Now some pro raw sites claim that cats' stomachs are maintained at a ph of 1 while human stomachs are at a much less acidic ph of 4-5. As far as we can determine, this is pure fiction, designed to mislead the ill informed or simply repeated by the misinformed. The human stomach ph typically varies from 1.5 to 3, with a nominal value of just over 2. What about cats? According to Nutrient Requirements of Dogs and Cats by National Research Council Ad Hoc Committee on Dog and Cat Nutrition: "The average ph of the cat stomach is 2.5 +/- 0.07 (Brosey et. al., 2000)." So cats and humans in fact maintain just about the same level of acidity in their stomachs. When a pro raw advocate tells you cats can ingest bacteria and bones with no problems due to their "highly acidic stomach acid," they are feeding you a bunch of pure rubbish.
But there are typically more (false) claims than just stomach acid.... [more coming soon!]
And what does the available science say? Can cats get sick from typical foodborne pathogens? YES! [more coming soon]