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.
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