Raw feeding has increased in popularity in recent years. While still a small portion of the pet food market, raw foods are definitely here to stay. Perhaps more so than any other type of feeding regimen, dog owners who feed raw are highly dedicated to this form of feeding.
To test this premise, try separating a dedicated raw feeder from his or her favorite food.
There are several options for owners who choose to feed raw. These include using a homemade recipe, purchasing a base mix that can be added to raw meat, or buying a frozen or freeze-dried complete and balanced product. For all of these forms, many health and wellness claims are being made:
Okay, the last one may be an exaggeration. Everyone knows that most dogs prefer Match.
Is there Evidence? Despite strong belief in these benefits (and the belief that believing strongly [and in all CAPS] makes the benefits more likely to be true), there has been a distinct lack of scientific evidence to support (or refute) them.
Until now. Last month, a group of researchers at the University of Illinois, led by Dr. Kelly Swanson, published research comparing the effects of feeding three types of food to dogs – raw, moderately cooked (also referred to as “fresh cooked”), and extruded (dry).
The Study: A group of eight adult dogs were fed four different diets on a rotating basis (1). Each food was fed for a 28-day period that included an adaptation phase (i.e. gradually switching to the new food), a phase to measure voluntary physical activity level, and a phase to collect total feces and urine output for digestibility calculations. The researchers also measured food intake and collected blood samples for serum chemistry measurements. The four foods that were studied were:
- Dry (extruded) food (Purina Dog Chow)
- Raw food (Freshpet Vital Raw)
- Moderately cooked, fresh food (Freshpet Roasted Meal)
- Moderately cooked, fresh food, grain-free (Freshpet Vital Roasted Grain-free)
Results: All of the foods were well-accepted by the dogs and the dogs remained healthy throughout the study period. Food comparisons showed the following:
- Food Digestibility: There were no significant differences in dry matter digestibility among the foods. The four products had coefficients ranging between 82.6 % [dry food] and 85.1 % [moderately cooked, grain-free]. The digestibility coefficient for the raw food was 83.6 %. It was not more digestible than either the extruded food or the moderately cooked foods. These digestibility values are considered to be moderate – not rock stars, but not poor quality, either.
- Protein Digestibility: There were significant differences in protein digestibility among the four foods. Protein in the moderately cooked, grain-free food was significantly higher (94.6 %) than the protein digestibility of the raw food (88.3 %) or the extruded food (85.1 %). The coefficient for the raw food was a bit lower than the researchers expected based upon previous work. However, a value of 88 % is still a respectable value and considered to be highly digestible.
- Poop quantity: Total fecal output (yes, researchers measure these things) was highest when the dogs were being fed the raw diet and lowest when the dogs were consuming the roasted, grain-free food. This difference was substantial – more than 100 grams per day when fed raw compared with 52 grams per day when fed the roasted, grain-free food. These differences became less dramatic (and not statistically significant) when expressed as either dry matter or a proportion of intake. However, the raw food continued to produce more fecal matter than the other products.
- Poop quality: All of the diets resulted in acceptable fecal quality. However, when fed the raw product, dogs produced feces that were softer than those produced when being fed any of the other three foods. These feces were still considered within the normal range of “firmness” however. Feeding the mildly cooked food resulted significantly higher fecal concentrations of two by-products of large intestinal protein fermentation – indole and phenol. The cause or health significance of this is not completely understood, but these two compounds are one source of “stinky poops” that owners may complain about.
- Gut microbes: All four of the products caused modifications in the intestinal microbiota. When dogs were consuming the raw or the moderately cooked, grain-free diets, overall microbial population diversity was reduced compared to when they were consuming the extruded food. Fecal microbial shifts that occurred in response to the raw or moderately cooked foods, which were high in protein and fat, were similar to the shifts that have been reported in human subjects consuming high-protein/high-fat diets. The researchers noted that these shifts – reduced species diversity, increased Fusobacteria and Proteobacteria, and decreased Actinobacteria – are in agreement with other recent reports of the effect of a raw diet on the dog’s gut microbiome (2,3,4). While this shift is generally considered to be negative in terms of health, all of the dogs in this study and others remained healthy while consuming the test diets. Therefore, the long-term effects of these changes are not known and require further study.
- Overall health: The dogs in this study remained healthy, had blood chemistry values within normal ranges, and showed normal activity levels. All of the products were well accepted and readily consumed. It is worth noting that more calories (kcal) per day were consumed when dogs were fed the raw food compared with then they were fed the extruded diet (1202 kcal/day vs. 806 kcal/day). This difference probably reflects the high palatability of the raw diet but also suggests that overconsumption of calories may have developed over long-term feeding of the raw food.
Take Away for Dog Folks: This study found that dogs accepted all three types of foods – extruded dry, moderately cooked, and raw – and remained healthy. Contrary to expectations (and claims), the raw food that was tested in this study was not significantly more digestible and did not result in less defecation or produce better quality feces. Although all four foods altered gut microbial populations, the shifts caused by the raw food are generally considered to be negative changes rather than positive. However, the complexity of the gut microbiome coupled with numerous factors that affect gut health prevent any conclusions about these changes.
So, where do we now stand with the claims box, above? Here you go:
Before the raw feeders come out in droves……..let me add a few points……
- This study tested four commercial foods. The dry, extruded product was Purina Dog Chow; the two moderately cooked foods and the raw food were Freshpet diets. All of these products are mass-marketed pet foods that are sold in supermarkets and are generally considered to be low to moderate in price point.
- We can only make conclusions about these foods – this is why the chart above states “no support” rather than “disproven”. The results of this study are based upon the foods that were compared and suggest that, given the information that we now have, certain blanket claims about raw foods are not supported. Clearly, this cannot and should not be extrapolated to all raw diets or all dry foods.
- Still……these results ARE important because they show that a dry food performed similarly to a raw and a moderately cooked food. My two cents? This probably has more to do with the type and quality of the starting ingredients that were used in these products much more than it has to do with raw versus cooked. By AAFCO definition, the term “chicken” can (and usually does) refer to chicken carcasses that remain after the removal of chicken meat for human consumption. These carcasses may either be processed into chicken meal for use in extruded foods or ground up and used in raw or moderately cooked foods. Same stuff, different processing.
- Last – The moderately cooked foods performed every bit as well as the raw food in most measures and a bit better on some. These data suggest that perceived benefits of feeding a raw diet over a diet that has been cooked at moderate temperatures are not supported. These data also suggest that there is nothing magical about making sure that a food is RAW. Rather, it is more important to consider the source and quality of the starting ingredients, the degree and severity of processing, and the nutrient content of the food.
(Note: Kudos to the research team for reporting brands. This is highly unusual with pet food studies – the vast majority of published papers do not identify either company or brand of the foods that they are testing).
- Algya KM, Cross T-WL, Leuck KN, Kastner ME, Baba T, Lye L, de Godoy MRC, Swanson KS. Apparent total-tract macronutrient digestibility, serum chemistry, urinalysis, and fecal characteristics, metabolites and microbiota of adult dogs fed extruded, mildly cooked, and raw diets. Journal of Animal Science 2018; 96:3670-3683.
- Beloshapka An, Dowd SE, Duclos L, Swanson KS. Comparison of fecal microbial communities of healthy adult dogs fed raw meat-based or extruded diets using 454 pyrosequencing. Journal of Animal Science 2011; 89; 89(E-suppl):284.
- Sandri MS, Dal Monego G, Conte S, Sgorlon B, Stefon B. Raw meat based diet influences faecal microbiome and end products of fermentation in healthy dogs. BMC Veterinary Research 2017; 13:65.
- Bermingham EN, Maclean P, Thaoma DG, Cave NJ, Young W. Key bacterial families (Clostridiaceae, Erysipelotrichaceae and Bacteroidaceae) are related to the digestion of protein and energy in dogs. PeerJ 5:e3019 https://doi.org/10.7717/peerj.3019
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44 thoughts on “A Few Raw Facts”
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Hey Linda! I enjoyed reading this. It’s very difficult these times to choose a good food for your pet. So many options but so little information for pet owners! I am a raw feeder myself, but I do use – I think – higher quality raw dog food than the ones mentioned above (also European dog food since I live there, no idea if there’s a lot of difference). I try to supplement with omega 3 and leftover veggies. Personally I saw a significant decrease in fecal matter with our dog. Before that the dog had a lot of diarrhea.
Do you know of any more scientifical studies on raw pet foods? I have an animal science background myself and am very interested in learning more about this subject and of course I would like to make the best possible choice for my dog.
Very interesting that Dog Chow, a dog food more often associated with low quality, held its own with the raw and cooked diets. I use Kirkland dry food myself. Can you point me to any studies comparing the quality of various commercial dog foods in terms of quality and health benefit?
Thanks for reporting on this study, Linda. It is very welcome, and I too hope that more studies like this one will be produced in the coming months and years. My own dogs were fed a commercial raw diet (Stella & Chewy, and Bravo brands), until one of them got diagnosed with hyperthyroidism recently. My vet immediately advised me to stop feeding raw, and I was wondering if you had reviewed those studies warning of that possible link? The studies seem to suggest that, in the slaughtering process, some thyroid tissue gets chopped up and ground into the raw meat, thus artificially raising the dog’s thyroid levels. At any rate, we found that the raw diet did NOT contribute to my dog’s hyperthyroidism, but I am still wary of going back to raw. I now feed my pups a combination of Honest Kitchen base, with home cooked ground beef or turkey (thank you, Instant Pot!), vegetables, rice, and some canned dog food. The diagnosis of my hyperthyroid chap is still unclear (but it’s not cancer), and he eats 3.5 lbs of food a day, and is still losing weight (he should weigh 90 lbs, but currently weighs 80 lbs)! Having calculated the costs, I find that this mixture of home cooked/HK/canned is costing me a very similar amount to what a raw diet would cost. By the way, I don’t feed my dogs any bones, as they always get runny tummies from them. I wish we knew more than we do!
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Hi Karen, Thanks for your note. I am sorry to hear about the hyperthyroidism in one of your dogs. Kudos to your vet for being up on this literature, as the possible connection between hyperthyroidism and raw feeding (or feeding tracheas as snacks) is pretty recent. I did write about these studies in The Science Dog, in a blog entitled “Got Gullet””. Here is the link: https://thesciencedog.wordpress.com/2015/10/29/got-gullet/ I think that a raw diet can be fine as far as hyperthyroidism goes, provided one has assurance from the manufacturer that the thyroid gland has been dissected from the meat sources that they are using. And, it goes without saying, that chicken or turkey necks are not being fed (as is common with some raw feeders). If you go with a company that guarantees “human grade” this would ensure this because foods intended for human consumption must have the thyroid gland removed and this is not required of foods intended for pet foods or other uses. Honest Kitchen is one of these companies (great company!), so you are in good stead there. If you are feeding HK plus homemade ingredients, it is pretty likely that the elevated thyroxine levels are not caused by diet for your pup. It sounds like you are in good hands with your vet – so hope you find out the underlying cause, as I know this can be both frightening and frustrating. Best wishes, Linda
I was excited to see your article, but I think the study was flawed by their choice of raw food product. As far as I can tell, Freshpet Vital Raw has been discontinued; there is no mention of it on their website and a link from one of their blog posts is broken. The only information I was able to find about this product was on another blog post on an unrelated site, entitled, “My Biased Review of Freshpet Vital Raw Patties.”
According to what I see in that blog post, this food is (was) very, very different from all other commercial raw products. It is refrigerated rather than frozen with some sort of undisclosed preservation process that is supposed to make it last six months unopened in the fridge, and there is no mention of it containing bone, which is one of the hallmarks of most raw diets, both commercial and homemade. As such, it simply doesn’t represent the type of raw diet that people are feeding, and so the results are not directly applicable. Many of the findings may be related to these differences rather than to the product being raw.
I hope they continue to do more studies with a better choice of products. Thanks for letting us know about this study, and for your insightful analysis.
Thank you for this! I, too, hope there will be more studies like this and ideally with larger sample sizes. But it’s just great to see something vs nothing, especially the details about poop and gut microbes! The ‘great debate’ that happens online doesn’t serve our dogs, it mostly just overwhelms dog guardians who genuinely want to do better but get pulled around in circles.
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Thanks for the nice review of the article. I do disagree, however, with this statement: “the vast majority of published papers do not identify either company or brand of the foods that they are testing.” That is not true. In reputable, peer-reviewed journals, the authors are required to disclose their affiliations and all potential conflicts of interest. And many, if not most, of them do disclose the brands – but often as footnotes. The ones that don’t disclose brands usually involve a new ‘test food’ (new nutrient blend, etc.) that isn’t yet on the market. Your remark may have been true in previous years, but it’s not the case now.
Hi Kim, Thanks for your note. Disclosing funding and conflicts of interest are not the same as disclosing brand names in test diets. The first is required by all peer reviewed journals; the latter is not. All of the studies that I report in The Science Dog are published in peer reviewed journals and this is one of the first that identifies the commercial pet food brand. Please feel welcome to read through other Science Dog articles and find the original papers (I always cite them). If they identified the brand name, I included it in the piece. Most do not, not even in footnotes. (And, if you find a paper that did and I missed it – please do pass it along as I would be more than happy to revise the piece and include these). Best, Linda Case
See Pottenger’s Cats: A study in Nutrition by Francis M Pottenger, M.D. A book about the 10 year study of cats fed raw and cooked food. Done from 1932-1942 this was the original research into the effects of diet on health. Very different conclusions from the above study and done over a much longer period and with several generations of cats. I also like to know who has funded any research. Do you know who funded the research you have cited above?
Seriously, you’re claiming a study done more than 50 years ago is more accurate? The quality of research back then was poor, as was attention to animal welfare, and there is no way that those results should be taken as valid while these are dismissed simply because you don’t like the results. If you read the article described above, it was performed by FreshPet. I suspect they were doing research to back up claims that their food was better. Kudos to them for publishing anyway. I agree with you that longer-term studies would be great. But those studies are quite expensive and labor-intensive, so they’re not often done.
I don’t think how long ago a study was done is significant. What would be significant is the design of the study. What was left out and who funded it. Wo did it, and where the results were published.
Personally I will go by my personal experience and absolutely pass on ANY food sold as ‘complete and balanced’ — for humans, dogs or cats! I like to know what is IN my food. I am unamused by needing to read the tiny, tiny print in a hard to find spot on the packaging to discover that the stuff that is sold as “Made with Kangaroo” has more meat from other sources than kangaroo. I was very, very distressed to “discover” that the Australian Made and owned food manufacturer had been bought out by ‘Uncle Ben (or notoriety) and had its ingredients totally — I would have preferred to have been informed BEFORE my dogs’ condition went off!
Hi Joy, Thanks for sharing this. Interestingly, the team of researchers who conducted the study that I review in this essay had two graduate students who did a series of studies with both domestic cats and exotic cat species (in zoos) and their responses to feeding a raw diet. They found that the cats did very well on the raw foods (similar to what you noted from the early studies), and that the foods had very high dry matter and protein digestibility coefficients (higher than what was found in this current study, but again, this was probably caused by the quality of the initial ingredients). If you are interested in the newer studies with cats, just search Google Scholar with Dr. Swanson’s name or the last names of the grad students. Kerr and Vester Boler. These are really cool studies – I just have not reported on them here because I stick to dog studies for this blog. Thanks for the information and for reading! Best, Linda
Cats are very different than dogs. They have very different nutritional needs. Cats can eat raw where dogs cannot.
Dogs can CERTAINLY ear raw! Before the days of commercial dry food, just about all dogs were fed on raw meat and raw bones. Mine still are!
Starchy food should be cooked and unless leafy veggies are juiced, then they are better fed cooked too,
Excellent review of the research – thank you. I am another who looks to the quality of ingredients, and one reason I cook for my dogs is so that I know precisely what they are getting (and because it is significantly cheaper than the high quality commercial stuff, of course!). The faecal results are particularly interesting – I have to say they are the opposite of what I see in my own animals. I must take a look at the ingredients of the foods used in the research, and see how they compare to my own dogs’ diet of meat, bone, offal, fish and vegetables.
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“one reason I cook for my dogs is so that I know precisely what they are getting”
It is super simple to know precisely what is in dog commercial food by reading the labels. It lists exactly what ingredients are there, what quantity and the content. The process is exactly the same as for human food: the ingredients, the quantity and the nutritional value.
I should laugh! But I am more sorry — this is why ‘manufacturers’ get away with murder! Do you read the ingredient on he packaging EVERY time you buy it?? And that goes for ‘human food’ too!
Of course! All the time if it is a new product and I want to know more. Why not?
In the UK ingredient labels typically say things like “meat and animal derivatives” or “derivatives of vegetable origin”. High quality foods may say which animal, but very few actually say which part of the animal – perhaps it is different where you live.
Jackie Phillips said “All the time if it is a new product and I want to know more.”
But the problem IS that companies change the ingredients in their foods without changing the packaging. When I discovered the ‘truth’ about “Bonnie” the bloke at the Produce store told me not only that it had been bought out by ‘Uncle Ben’, but that they had changed the ingredients many times over the period they owned it!
Hi Frances – Thanks for your note. I agree with the feces results being unexpected and puzzling and suspect that the most important factor was in the starting ingredients. Best wishes, Linda
Interesting study. I would have expected more differences between the diets. We feed a mostly dry diet and our guy get some of whatever we are having for dinner. We periodically rotate through several different high quality dry foods. He is now our 4th Great Dane we have fed this way. While we lost one guy at 8 the others all reached at least 13 and our current guy turns 15 in 2 weeks.
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Hi Frederick, Thanks for your note. So wonderful that you have had Danes who live to such great ages – and 15 – wow! That is just tremendous and such a gift. Hope your boy continues to do well – whatever you are doing, certainly keep on doing it! Best, Linda
Fantastic reporting on this study. I am so grateful I heard you on a podcast recently. And from that, found your blog. You are so good at accurately presenting the details of a study and doing so without bias. I’ve been struggling to sort out the science from the passion when it comes to feeding my dog. Like everyone, I want to do what is nutritionally best for her. I appreciate your work. Carol
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Hi Carol, Thanks for your note and kind words. “Sorting out the science from the passion” is a great and very apropos expression! Thanks for reading and for commenting! Best, Linda
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I see, though, that ALL these foods were ‘commercial mixes’. It seems to me that the problems are with ‘commercial pre-prepared food, rather than way versus cooked.
And it is not so much what is missing in the commercial food, but what is there that isn’t good.
Having worked, as a girl in a ‘food factory’ and seen the quality of foods going into HUMAN grade food, I am very wary of any factory produced dog foods 😦
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When exactly did you work in these factories and what country and what brands of food?
1960. A ‘Pickle’ factory.
The spoiled stuff/unsold stuff from the ‘markets’ were ‘pickle, The spoiled pickles were turned into mustard pickles. It put me off pickles for life 😦
I also have younger friends who have worked in canning factories and heard their repots of the stuff that goes into the cans.
A current friend used to work at a pet food factory. He told us that you could SMELL the meat coming in from the abattoir as soon as it had started to thaw. (No they do NOT use ‘fresh’!)
(Unless you are Australian the brands would mean nothing to you
Super interesting study! I am a raw feeder of several years now – started when my old guy began going off his super-premium kibble (this a dog who LOVES his food). He was having some health issues at the time (auto immune disease – SLO). I won’t say raw cured him, but he loved it from the start and still eats with gusto, now 13 years old. His SLO has been in remission for many years, and vet visits are rare. I did kibble/raw with my other two for several years before finally switching to a DIY raw (grind) for all meals about 2 years ago. They all love it. I will agree with the stool observations – the old guy’s poop is pretty economical, but my Rottweiler, not so much. I would have expected better digestibility with raw, and even wonder if a better quality dry/extruded would have outperformed raw. But I’ll stick with the raw for now (frankly don’t have time to cook for three large dogs!). It’s working, and I’m constantly learning and fine tuning ingredients and nutrients. I like knowing what they’re eating – this is huge for me, given all the food recalls. Plus, did I mention they love it? Thanks for a great post.
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Hi mcfwriter – Thanks for your note. I agree about the quality issue. No reason at all for you to change of course – imho, this research provides some needed information about commercial foods (both raw and cooked and extruded) that is helpful. One study should never mean that someone should stop feeding in a way that works for them and is keeping their dog healthy and happy! Thanks for reading and for posting! Linda
The study lasted 28 days. Impossible to draw conclusions about the most important benefits of a high quality diet – overall health and longevity. Not a very useful study, IMO.
Hello Rex the Wonder Dog, Yes, point taken. However, 28 days is plenty long enough to evaluate a foods nutrient content, digestibility, effects on the gut microbiome (which is of great interest to both human and companion animal nutritionists), and fecal quality. These studies are tremendously expensive to run and remember that these are actual dogs who are being studied so there are ethical and animal care/welfare considerations as well. So, for the objectives that the researchers presented (they did not profess to speak to long-term health or longevity effects), imho, it is a pretty nice study that provides us with some helpful and interesting information. Thanks for posting and for reading! Linda
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It’s my understanding that pet food that has an AAFCO label only has to have something like 6 months of being fed to dogs to get the label, providing that they meet nutritional guidelines. I don’t think any particular brand of dog food does any longevity studies before going on the market or being certified. The only way that you can absolutely control their meals their entire lives is by making sure they live in cages in a laboratory. So by insisting on longevity trials you’re pretty much saying you want more animals in labs. Some food companies do feeding trials for pets at home but it’s far different doing a few months at home vs 15 years and also controlling for health problems the animal is genetically predisposed to. Most lab dogs are specifically bred with specific traits and health so they test a very similar population. It’s just a lot more complicated than saying “I want to see how long animals live when eating this food”
To blargh, if you are replying to my comment: I’m definitely not saying I “want more animals in labs!” I’m not “insisting on longevity trials.” I also didn’t say “I want to see how long animals live when eating this food.” I am saying that I didn’t find the results of this study very useful. No information that would convince me to change the way I feed my dogs. I do think there may be plenty of anecdotal evidence that could be analyzed to draw conclusions about the effects of diet on overall health and longevity. In fact, I’d be surprised if this hasn’t been done. That’s the kind of information I would find useful. Not sure why you felt the need to jump on me with your comment; hope it was a misunderstanding.🙂
Cool. Thanks for sharing. Hope we see more of these type of studies. I’m more and more in the camp of quality ingredients vs the dogma of raw feeding. This type of study will only help us all to make good decisions. Now if we could just get companies to disclose product sourcing information…
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Hi April – You are welcome! I too hope that we see more of these. We are totally on the same page regarding quality ingredients…..and needing to get the correct information into the hands of owners so that they can make informed decisions for their dogs……Ahhh…..in a perfect world…..
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Try to pull my high quality kibble from my hands.
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🙂 🙂 🙂
What about commercial canned “wet” diets?
Hi David – This particular study did not examine retorted (wet/canned) products. Will keep my eyes open for any that do, though! Linda