There is a great deal of confusion (and opinion) today regarding how to classify the domestic dog. Those who identify dogs as carnivores (meat-eating) animals tend to focus on the predatory nature of the dog’s closest cousin, the wolf. Conversely, those who are inclined to classify the dog as an omnivore (consumes both plants and meat) rely upon the dog’s scavenging nature and ability to consume and digest a wide variety of food types. So, which is it? And, perhaps more importantly why does what we call the dog, carnivore or omnivore, seem to matter so much to us? (And why do discussions about this issue seem to quickly escalate into shrillness, name-calling and spamming?)
First, let’s all just calm down. From a scientific viewpoint, it appears that some confusion may arise from the dual use of the term “carnivore”. This term is used as both a taxonomic classification and as a description of a species’ feeding behavior and nutrient needs. Both dogs and cats are classified within the taxonomic order of “Carnivora”, a diverse group of mammals that includes over 280 different species.
Some eat meat…..some don’t: While many of the species within Carnivora hunt and consume meat, not all are predatory or nutritionally carnivorous. The species within the order Carnivora vary considerably in the degree of dependency that they have upon a meat-based diet. For example, all of the cat species, including our domestic cat, Felis catus, are obligate carnivores. In contrast, bears and raccoons consume both plant and animal foods, while the Giant Panda subsists on a vegetarian diet. Therefore, while all of the species within the order called Carnivora can eat meat, their typical feeding behaviors exist along a broader spectrum, ranging from the obligate carnivores at one end to animals that are almost completely herbivorous at the other end.
So, where does the dog fall along this spectrum?
Cats vs Dogs: Let’s consider this question by comparing our two best animal friends, the dog and the cat. The label “obligate carnivore” (sometimes called true carnivore) means that the cat is incapable of surviving on a vegetarian diet and must have at least some meat (animal tissue) in its diet. This means that a diet that is composed of all plant materials cannot meet all of the cat’s essential nutrient needs. Specific nutrients that are problematic if Fluffy is fed a vegetarian diet include Vitamin A, a type of amino acid called taurine, and an essential fatty acid called arachidonic acid. All three of these nutrients are found in a form that cats can use in meat products and but are not found in plant foods. During evolution, cats either lost or never developed the ability to produce these nutrients in the body from the precursor forms that are found in plant foods.
The Adaptable Canine: In contrast, most of the canid species, including the domestic dog, are more generalist in their eating habits and subsequently in their nutrient needs. In the wild, wolves and coyotes exist as opportunistic predators, hunting and eating the type of prey that happens to be available. In addition to the flesh of their prey, wild canids readily consume viscera (stomach, intestines) which contain partially digested plant matter. Canid species also scavenge carrion and garbage and regularly consume fruits, berries, mushrooms, and a variety of other plant materials. Similar to its wild cousins, the domestic dog is a predatory species that also consumes plant foods and scavenges, and is capable of consuming and obtaining nutrition from a wide variety of food types.
Not only does the dog naturally choose a wider variety of foods to eat than do cats; the dog is capable of deriving needed nutrients from plant foods more efficiently than do cats. Let’s look at the three nutrients that we mentioned earlier; Vitamin A, taurine and arachidonic acid:
Finally, anatomically, dogs’ gastrointestinal tracts, from their mouths to their intestines, are consistent with other predatory species (i.e. meat-eating) that consume a varied diet. They have some ability to grind food (molars), and possess a small intestine that is longer in length (relative to body size) than that of obligate carnivores, but that is shorter in length than that of herbivorous species.
Altogether, the nutrient, metabolic, and anatomical characteristics of dogs place them on the omnivorous side of the spectrum within the wide range of species who hunt prey, scavenge, and consume plant foods
When we look at the evidence, we see that both nutritionally and taxonomically, the dog is best classified as an omnivore, an animal that consumes and derives nutrition from both animal and plant food sources. More specifically, the dog evolved from a species that made its living primarily through hunting and consuming prey but that also consumed whatever was available through scavenging. (Anyone who lives with a Golden Retriever is well acquainted with the scavenging part).
Time to drag out the box.
So, why is it that we read multiple websites, listen to certain “experts” and talk to Joe next door (who happens to know a lot about dogs) and they insist that the dog is an (obligate) carnivore? Why are some folks so incredibly (and one might venture, obsessively) invested in this belief? Not to put too fine a point on it, many proponents of the “dog as carnivore” hold on to this conviction like a dog with a meaty bone. One may wonder, why is this distinction even important, except perhaps for academic interest?
My own opinion is that the keen interest that we see in recent years is caused by an unusual and somewhat unprecedented focus on a desire to “feed dogs naturally.” Oddly enough, prior to the development of commercially prepared dog foods in the early 1900’s, domestic dogs were fed naturally – they were fed scraps of human food…..in other words, they scavenged. So, we appear to have come full circle, with the only difference being that the fervent adherence to a mantra of “feeding dogs naturally” now focuses on the dog’s hunting and meat-eating history rather than on its equally significant existence as a proficient scavenger.
Do dogs thrive on diets that include animal-based ingredients (i.e. meat, poultry, fish) – Yes, definitely (and especially if those ingredients are of high quality). Do dogs enjoy (and probably prefer) meat in their diets. Probably. Do dogs have a nutritional requirement for animal-based ingredients in their diets? No, they do not.
EXCERPTED FROM: Dog Food Logic: Making Smart Decisions for Your Dog in an Age of Too Many Choices, by Linda P. Case (click below for purchasing in formation).
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Another great article – they always make me think and reevaluate my personal biases! I am curious, in your opinion, can a dog, or a wolf, eat a completely herbivorous diet and meet all of its nutrient requirements without any synthetic supplementation? Could such a diet be high enough in protein?
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Thanks for sharing
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Great summary! and I’d add this link from the great James O’Heare for the ones who want to try even a vegan routine 🙂 (I didnt yet) http://www.behavetech.com/vegandogs.pdf
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Ah, a rare instance of good sense and science applied to the question of dog food! Feeling grateful!
One other aspect that fits in here is dogs’ ability to digest starch better than, say, wolves.
I’m a vegan and feed my dogs 90% plant matter (which I cook myself: lentils, sweet potatoes, brown rice, carrots, green leafy veggies, broccoli etc) and 10% green bison tripe and mussels. I’ve never dared to go 100% plant-based, even with supplementation of DHA/EPA, calcium etc. But I have offered the usual plant mix I feed to my dogs without the tripe on occasion. To my amazement, they eat that just as happily as with the tripe!
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Thanks for your response Linda. Now I know where all those good articles are hiding 🙂 I’m looking forward to reading Beware the Straw Man!
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HI Linda-
Great post. Being vegan, I like to reduce my dogs consumption of farm animals and it’s good to know I need not feel guilty about this as long as I’m providing them all the nutrients they need.
Question for you…is there a search feature on your blog? I have tried searching for your previous articles but have had a hard time locating them.
Thanks,
Julie
Julie Posluns Rover Achiever Pet Care Inc. 416.476.6846 • http://www.roverachiever.com
M.Sc. Candidate, Cognitive and Behavioural Ecology Program Memorial University of Newfoundland
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Hi Julie! Thanks for your comment. Dogs can be fed a vegetarian diet. There is some evidence in giant breed dogs (specifically only Newfoundlands and Irish Wolfhounds have been studied, to my knowledge) for a dietary requirement for taurine, a type of amino acid that cats definitely require in the diet and dogs do not (with some exceptions, possibly). To be safe, if you are feeding a vegan or vegetarian diet, I would suggest making certain that the diet is fortified with taurine. Regarding Science Dog essays – if you are interested in reading most of the first 18 months essays, which focused on behavior and training, your best bet is to buy “Beware the Straw Man”. It is available both as print and on Kindle and there is a link on this site. If you are interested in learning more about nutrition and feeding, my book “Dog Food Logic’ (which is not part of the blog, with the exception of several excerpts) is available through Dog Wise. I keep a lot of the Science Dog essays up for a period of time and then “retire” them when they go into a book to encourage readers to get the books! 🙂 (Some, I leave up on the site for longer than others). Thanks for reading! And, BTW – Love your Rover Achiever site! What a great service you provide! Linda
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I am confused. In the last paragraph you say, “Do dogs thrive on diets that include animal based ingredients? Yes definitely…….Do dogs have a nutritional requirement for animal based ingredients in their diet? No, they do not.” How can they thrive on a diet that is not nutritionally required? I feed mine a commercial raw that is around 70% animal based and 30% plant based. I also supplement with additional plant matter. I’m by no means a raw purist, but I’ve certainly seen quantifiable evidence through appearance and blood work that two of mine have benefitted from this diet. The other was weaned to this diet as a pup so I’ve no idea as to benefit for her.
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Hi Laura, Because they are omnivores – they consume a variety of foods, including both animal and plant foods, and , like humans and other omnivores, can meet all of their essential nutrient requirements through consuming plants. So, while dogs can thrive on a diet containing animal-based ingredients, so too can they thrive (and develop no nutrient deficiencies) when fed a vegetarian diet. It is in this way that dogs differ from cats, who are obligate carnivores. Because dogs also evolved as a hunting (some say opportunistic) species, they do show a definite preference for meat in their diet. However, having a preference for certain dietary ingredients is not the same as having an essential nutrient requirement. In fact, preferences for certain foods can easily lead to nutrient imbalances and deficiencies. (I have a strong preference for Ben & Jerry’s Cookies and Cream ice cream, but if I consumed excessive amounts, this would certainly not be a balanced diet for me). In the case of dogs, we see this confusion between preference for certain ingredients/foods and poor diet choice when dogs are fed a diet that is composed almost exclusively of muscle meat, which leads to, among other problems, calcium deficiency and an imbalanced Ca:P ratio. If you read the previous essay, “Got Gullet”, you will know that there is also evidence that feeding dogs a large amount of certain beef animal body parts can lead to health problems. It is without question that dogs are nutritionally omnivorous, because they do not have to eat animal flesh to obtain all of their essential nutrients. Just like humans can eat a variety of different types of diets and be healthy, so too can dogs. While I am sure that your dogs are very healthy on the diet that you feed, your experience does not mean that other diets for dogs are nutritionally inferior or that dogs do not thrive when fed other types of foods. Rather diets that dogs are fed must be evaluated in terms of their nutrient balance, the quality of their ingredients, the availability of nutrients to the dog, and in this day and age, food safety. Conversely, simply classifying a food as “appropriate or inappropriate” based upon the amount of animal flesh it contains or whether or not it is fed raw or cooked does not adequately assess a diet. Linda Case
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I am only speaking in terms of my own dogs and the way they’ve thrived on their current diet, not all dogs in general. I was unsure how a body could thrive on non essential nutrients. I haven’t read the essay Got Gullet yet, but I will. I am interested in doing the best I can, nutritionally for my dogs. I rotate through about 5 different proteins and one of my dogs can not tolerate beef but, neither can I.
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Hi Laura, Sure, I understand completely (and it sounds like you are doing a great job with your dogs). And, to reiterate, all that being omnivore means is that dogs are capable of consuming both plants and animals in their diet and can obtain all of the essential nutrients that they need from plant sources. Cats, as obligate carnivores need at least some animal source ingredients in their diets. (The table shown in the essay reports three of the most important nutrients that this pertains to). Thanks for reading and for participating – glad to have you here! Linda
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On a related note, this article from 2010 popped up in my FB feed this morning. Some similar content regarding the evolutionary history and domestication of dogs and how that relates to diet.
https://www.sciencebasedmedicine.org/raw-meat-and-bone-diets-for-dogs-its-enough-to-make-you-barf/
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Hi Tom! Love Brenden McKenzie (He is “The SkepVet, btw)! Thanks for posting his article!
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Hi Linda, great article. I recently met with someone who is saying he’s a dog expert and that dogs only need meat and that that the AAFCO standard is rubbish. I think he’s combined a passion for a raw diet with his feelings of anti-AAFCO and gone off-base. I recommend and also feed my dog an omnivorous diet. As I right this, she’s got a home-cooked portion being prepared on the stove which is lambs liver and broccoli (which will serve as a topper to a commercial food).
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Hi DoggyMom – Yikes. Only need meat. Dangerous advice. Good to hear that you did not listen (and recommended another approach). Thanks for writing in!
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great article Linda! I have been thinking about this topic alot lately since I have two dogs that seem to really need and seek out grass, berries, and other plant materials. It made me wonder if my dog food is too high in meat. I know dogs have evolved alongside humans for longer than most believe. I really need to read your book. Thanks for sharing. Your writing is so refreshingly full of scientific evidence!
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Thanks Kathleen! Loved the video that you posted on FB – thanks for sharing that!
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One way to avoid this confusion is that a lot of taxonomists use the term “Carnivoran” for members of the order Carnivora, which includes giant pandas, which don’t eat very much meat at all.
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I also find the broader ecological/economic picture interesting.
Modern dogs remain scavengers in an industrial sort of way. What would society do with all its meat by-products and unmarketable cuts if it couldn’t dry and grind and mix them to make dog food? It’s no surprise that chicken byproduct creep into so many dry dogfoods . . . unlike beef, sheep, and pigs, you can’t use chicken leather, and chicken bone is much easier to process than the bones of other meat animals. Kinda looks like fish is following chicken: heads, skins and bones are now being diverted for dog food . . . along with being made into fertilizer.
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Excellent points, JenR and totally agree that the industrial age has presented us with, if you will, highly processed scavenging opportunities for dogs. I was at a gathering recently of a bunch of dog folks, many who are academics here at the U of IL. One person, an economist, made the point that putting all of the animal by-products into pet foods is a sustainable and highly economical approach to using all parts of food animals. (Marion Nestle makes the same point in one of her books). While factually true, I would counter that argument with the observation that we humans are keeping all of the high quality parts of these food animals for our own consumption, while putting only the parts that we do not want, or cannot consume or that are tarnished in some way into pet foods. IMHO, while these by-products can produce foods that are anywhere from very low to moderate/high quality, pet owners deserve to have more choices that are truly choice – i.e. foods made for dogs that come from human grade ingredients. While there are a handful of companies doing this (kudos to them all!), the selection is very small and limited to certain types of foods. While this is a bit off-topic, I think your observations about chicken and fish are spot-on in showing that we really continue to feed our dogs as scavengers )(with little choice of anything else for owners who do not wish to home prepare meals, but would like to feed a food made with higher quality ingredients).
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Actually high quality meat the way you describe it is a matter of culture and marketing. We now for example, consider white breast meat the best part of chicken and turkey, in first world America, but in fact, red meat and organs and blood contain far greater concentrations of nutrients than plain, lowfat white breast meat.
As do bones to some degree.
What we consider by products is what a lot of canids, wild and domestic, would choose!
And it’s also what a lot of old world people still choose to cook with. And live on for a long time, often without the heart disease, diabetes and obesity we have in the USA.
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No, pets are not fed the by-products to which you refer. The difference is that the way in which by-products are used in pet foods is almost exclusively in the form of processed animal meals and by-product meals. These contain the organ meats to which you refer (and which are of high quality protein), and they also include chicken heads, feet and “frames”. Because the consumer cannot know the proportions of these different components in a given meal, the range in protein quality of these meals is very wide. This is fact, not supposition, as there are numerous published academic studies comparing meals. Moreover, quality information is never available to consumers. Therein lies the problem – while certain by-products (organ meats, for example) can be of high quality if they are handled in the same commodity stream as human-grade meats (and, in fact, they are never handled in this way if they are on their way to a rendering plant) and if they are not processed into a meal, then perhaps your argument has merit. However, the way in which by-products are actually fed to dogs and cats is definitely not the same as those that “old world people chose to work with”. If you would like to learn more about this, see the essay entitled, “What’s the Deal with Meals”. Linda Case
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You are right – there has been an inordinate amount of conclusion-based evidence making in this area, and as soon as anyone’s profits depend on a disseminating a particular point of view then balanced discussion goes out through the window.
One minor point of fact; not all canids are omnivores – African wild dogs (Lycaon pictus) are pure carnivores specialising on hunted prey. They scavenge very rarely, and when they do it is on the carcases of other predators’ kills.
And a more significant point of fact; you write “taxonomically, the dog is best classified as an omnivore” but in fact they are, as you say early on, members of the order Carnivora. No animal is taxonomically classified as an omnivore, – there is no taxonomic category of “Omnivora”.
Should dogs’ diets be described as “vegetarian” or as “vegetable”, as in plant ?. “Vegetarian(ism)” is a lifestyle choice for humans, a dog that lives on a plant diet is a herbivore, not a vegetarian. It sounds picky, I know, but “vegetarian” has its own considerable load of baggage that clouds any argument about what is best (from the dogs’ point of view) for dogs to eat.
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