Raw Food Diet for Dogs: What You Need to Know

By February 3, 2022 Dog Diet, Dog Health, Dog Nutrition 0 Comments

Raw Food Diet for Dogs: What You Need to Know

Raw food diets for dogs have become a hugely popular trend amongst pet owners. People who want to provide the best diet for their pets often look for veterinary opinions about food options.

Fortunately, vets can now provide pet owners with well-informed guidance. They are benefiting from a sizeable accumulation of scientific literature over the past few years, which looks into the nutritional benefits and risks, including those of infectious disease, as well as public health implications, of raw meat diet for dogs.

Table of Content:

What Is Raw Food Diet for Dogs

Raw meat-based diets (RMBDs) for dogs are comprised of uncooked ingredients, derived from either domesticated or wild-caught food animals. These ingredients can include everything from skeletal muscles, internal organs, bones from mammals, fish or poultry and unpasteurized milk and uncooked eggs.

Raw meat diet for dogs can be crudely divided into two separate categories: commercial and home-made.

Commercial Raw Meat Diet for Dogs

The most typical forms of commercial raw meat diet for dogs are fresh, frozen and freeze-dried diets, which are supposed to be nutritionally complete and balanced. Such diets are typically formulated to comply with values specified in the AAFCO Dog Food Nutrient Profiles, and some of them may meet values specified for adult maintenance, growth, gestation-lactation or all life stages.

Yet, some of these diets may be intended for intermittent or supplemental feeding only, which is to say that they are not necessarily nutritionally complete and balanced. Commercial RMBDs are often based on recipes developed by or for a company, which sells them under a specific brand of pet food. Such raw dog food brands are produced in large quantities in industrial food manufacturing facilities and then packaged into smaller volumes, to be then sold to consumers.

Then there is a plethora of raw dried or freeze-dried dog treats, which carry bacterial risks similar to those for RMBDs. Such treats include rawhide chews, pig ears and cattle hooves, which have all been commercially available for a number of years, though have now been expanded to include hearts, tracheas and even bull or steer penises (marketed as bully or pizzle sticks).

Most freeze-dried treats (e.g. liver treats) are raw. Multiple studies have found that there is a high risk for contamination of these products with Salmonella spp and other bacteria and outbreaks of salmonellosis in humans have also been reported (as we will see below).

Quite apart from the fresh, frozen, and freeze-dried commercial raw food diet for dogs, a less common form of RMBD is a carbohydrate mix of grains, vitamins and minerals, which is intended to deliver a raw meat protein source, to be added to the pet’s regular food, for a more complete diet.

Home-Made Raw Meat Diet for Dogs

Home-made raw dog food, in contrast, features a number of different feeding regimens, such as BARF (originally designating a bones and raw food diet, though now it may mean different things to different people), the Ultimate Diet and the Volhard Diet.

Apart from the more popular ones, and as might be expected, a great variety of other home-made RMBD recipes have been developed by general practice veterinarians, trainers, breeders, as well as pet owners. Many of them include byproducts (such as bones and organ meat), though such ingredients are avoided by some owners because of personal preferences or misperceptions about what these are. Such misperceptions have led some producers of commercial foods to market brands specifically as containing no byproducts.

Some commercial raw meat diet for dogs are often intended to meet AAFCO nutrient guidelines and are marketed to provide the exclusive nutrition source for a specific stage of a dog’s life. Home-made RMBDs, in comparison, are often based on a rotation of ingredients — a strategy based on the belief that such a rotational variety may provide dogs, over a given period, with a balanced diet of essential amino acids, fatty acids, vitamins and minerals.

What’s Behind the Rise of Raw Food Diets for Dogs?

A survey of dog owners found that only 9 percent of those feeding a raw meat-based diet consulted with a veterinarian, before starting their pets on it, and most did not trust veterinary advice with respect to nutrition anyway. Of the same group of respondents, 20 percent relied on online resources to determine what or how much raw meat to feed.

Over the past couple of decades, a growing number of dog owners have parted ways with conventional, veterinary recommended, commercial diets in favor of more “natural” and “homemade” options. This trend has been partly driven by a similar movement in the human food marketplace for natural and organic products.

Furthermore, and quite apart from concerns about commercial foods, there are many additional factors that influence this change in pet owners’ dog food preferences.

To begin with, and unlike veterinarians and researchers, most dog owners look at feeding their pets in much the same way they approach feeding their families. While nutrition is important in food selection, there are also social and cultural aspects to food choices and feeding practices.

Ingredients included in commercial dog food are often byproducts of the human food industry. Though typically quite nutritional and healthy, dog owners would not choose to eat these types of foods themselves. But some dog owners would then go a step further and question feeding these items to their pets.

Then there is the question of food’s social significance to humans. As dogs become more closely associated with the family unit, the desire to prepare home food for them as well becomes greater.

Moreover, feeding dogs is a means by which people can exert some level of control and feel empowered in influencing the health and well-being of their four-legged companions.

All these trends, and perhaps other factors as well, have combined to give rise to some increasingly popular trends in unconventional pet food and the raw meat diet for dogs is possibly the most prominent among them.

Pet owners and veterinarians are deluged with information and opinions regarding raw dog food. But how is all of this information evaluated? And what criteria can be used to make rational, safe decisions?

How Did the Raw Dog Food Trend Start?

Many pet owners have gradually come to believe that providing an ancestral type of diet, one that mimics that of wild animals, such as a raw-meat based diet, is nutritionally superior to commercial pet diets. So, the diet of wolves or wild cats is based on what is available to support the animals’ survival, as well as their ability to pass along their genes.

The diet of our domesticated cats and dogs, in contrast, should not only support their survival, but optimize health and well-being for a long, fulfilling life.

It is important to realize that, while dogs are members of the order Carnivora, their metabolism and nutritional needs resemble those of omnivores. Furthermore, domesticated dogs are not like wolves in that they are adapted to thrive on a starch-rich diet. This is likely a result of their scavenger-like behavior, following their integration with human populations.

Genes that play a role in starch digestion, including pancreatic amylase, maltaseglucoamylase, and the sodium / glucose cotransporter show changes, such as expression and activity, which favor starch digestion in the dog when compared to wolves.

See, over the millennia dogs have lived among humans, they have adapted to an omnivorous diet and as a result can consume a variety of plant and animal products to meet their essential nutritional requirements. Moreover, dogs have gone through a variety of external pressures resulting in huge phenotypic differences from their ancestors, as well as among current breeds.

In fact, researchers have found that there are 36 regions of the genome, which differ between dogs and wolves, 10 of which play a crucial role in starch digestion and fat metabolism. The study concluded that these genetic differences between dogs and wolves were a crucial step in the early domestication of dogs.

The important thing to understand here is that, even as the wolf’s diet may be optimal for the reproduction and survival of a species whose lifespan is usually quite short, such a diet is not necessarily optimal for domestic dogs whose owners are doing everything possible to ensure that their pets will lead long, healthy and stress-free lives.

What Attracts Dog Owners to Raw Diets for Dogs?

Proponents of raw dog food diets, either commercial or home-made, often claim that they are both nutritionally superior and healthier. Many claims of potential benefits, however, are neither proven nor based on scientific evidence. Yet, they seem plausible enough to well-meaning pet owners, who do want to feed the best available diet that will prove most beneficial to their pets.

Some of the benefits ascribed to raw food diets for dogs include better palatability, cleaner teeth from chewing bones, a shinier coat and, as we have already seen, an owner perception that such diets are more natural.

Moreover, it is often difficult for owners to fully understand the effects of medical procedures, treatments, and disease processes, even as their pets’ food is among the most important factors, which exerts direct influence over the well-being of their pets.

In a way, what dog owners feed their pets can be every bit as important, and sometimes even more so, as what owners themselves eat. They would care for their pet as they would for a human family member, and the act of feeding sometimes becomes a way of strengthening the human-pet bond.

Owners naturally want to do what is best for their dogs and feeding is among the most important ways can they show their commitment. Yet, the pet food segment is hugely complicated and generates many, and often passionately expressed, opposing viewpoints. Some of the most emotional arguments concerning dog health and well-being involve the feeding of raw dog food.

Are Raw Dog Food Diets Healthier?

Proponents of raw meat diet for dogs report numerous benefits, but, at this time, there are no scientific studies showing any health benefits from raw meat diets. There have been studies, which have shown a small increase in digestibility from raw meat diet for dogs compared to regular commercial dry diets.

However, this result may be due to the ingredients, rather than the fact the diet was raw (these studies did not compare the raw diet for dogs to a diet that was cooked). While the effects of the small difference in digestibility necessitate further research, they do not seem to provide sufficient evidence to counterbalance the potential risks for raw meat diets.

An increasing number of studies are demonstrating valid concerns for nutritional imbalances and various health risks to the pets, as well as to their human owners. As of now, there is no conclusive proof of any health benefits beyond a few anecdotes. What we do have is proof that there are real risks, as we will see below, so pet owners should examine their options very carefully, before initiating raw meat diet for dogs.

Does Cooking Reduce Dog Food’s Digestibility?

Boosters often claim that one of the benefits of raw meat diets for dogs is increased digestibility because enzymes are not destroyed by cooking. While most dogs do not require exogenous enzymes, researchers have found improvements of food digestibility in pets fed raw meat diets.

Researchers have found that, among wild cats, RMBDs had substantially higher digestibility for crude protein, though not for fat, energy or dry matter. Another study, this one among sand cats, found higher amounts of dry matter, energy and protein in raw meat-based diets, however a statistical comparison was not performed.

Lower digestibility of cooked foods is thought to be the result of heat processing’s effects on proteins and amino acids. One study of domestic cats found substantially higher levels of both energy (8.0 percent higher) and macronutrient (4.6 percent to 14.3 percent higher) digestibility of an RMBD, compared to dry extruded diet.

Improvements in digestibility may be the result of the positive effects of the RMBD on digestibility, as well as of negative effects of extruded diets in general or the specific negative effects of the extruded diet used in this particular study.

Proteins and amino acids are significantly changed during the manufacturing process of pet foods. Processing conditions, most importantly heat application, but also pressure and water content, can have substantial effects on the digestibility of proteins and the bioavailability of amino acids.

The complete effects are dependent on the ingredients, temperature and type of processing (e.g. canning, extrusion used in the production of most commercial dry pet foods and freezing or freeze-drying that would be performed with commercial RMBDs).

Moreover, food proteins can react with other food components, including sugars, fats, oxidizing agents, acids, alkalies, polyphenols and food additives. The application of heat during the processing of dry extruded or moist pet foods usually results in the denaturing of proteins and the loss of secondary and tertiary protein structure.

While bioavailability of proteins may increase through collagen breakdown and a higher exposure to an animal’s digestive enzymes, it can also have a negative effect on amino acids through proteolysis, protein cross-linking, amino acid racemization, protein-polyphenol reactions, oxidative reactions and browning or Maillard reactions. The most significant losses of amino acids occur during the Maillard reaction.

Though heat processing may have certain negative effects on animal tissue proteins, it can also improve the bioavailability of some plant proteins, secondary to denaturing of antinutritional factors. Legumes, for instance, contain trypsin and chymotrypsin inhibitors that reduce both protein digestion and bioavailability. These inhibitors are denatured during heat processing, increasing protein bioavailability.

Improved digestibility leads to less digesta in the colon, with less fecal matter. Decreased fecal output, perceived as a benefit by some owners, has been found in a study of feral cats and in experiments.

While non-digestible carbohydrates, such as fiber, are beneficial to the host, undigested dietary protein leads to higher amounts of colonic compounds, including ammonia, phenols, indoles and amines, which have a role in diseases, such as colorectal cancer.

Heterocyclic amines are formed when muscle meat is cooked under high temperature. High concentrations (e.g. milligram / gram of food) of these compounds in the animal’s food has been associated with cancer in research animals. Concentrations in both pet and human foods have been found to be much lower (nanograms / gram of food), yet they still may have mutagenic activity.

Improved immune function is another frequently cited benefit of raw meat diets for dogs. In some experiments domestic cats fed a raw meat diet for 10 weeks showed a significant increase in lymphocyte and immunoglobulin production, while cats fed a cooked commercial moist diet showed no significant changes.

Raw Dog Food Nutritional Concerns

A 2001 study tested three home-made and two commercial raw meat diets for dogs and found they all had multiple nutritional imbalances, some of which may have important adverse effects on the health of the animals. These included a calcium-to-phosphorus ratio of 0.20, concentrations of vitamins A and E below the minimum detectable value, as well as a vitamin D concentration almost twice the AAFCO maximum amount.

A study in Europe calculated amounts of 12 nutrients (including calcium, phosphorus and vitamin A) for 95 homemade raw meat diets for dogs, as reported by the dog owners. It found that 57 (60 percent) diets had major nutritional imbalances.

Moreover, even when the raw food diets for dogs meet the minimum nutrient amounts and do not exceed maximum amounts, they may still not deliver the optimal nutrient amounts. To take one example, many raw meat diets for dogs are high in fat, compared with typical dry extruded or moist pet foods. This may make the pet’s coat seem shinier, but it may also cause mild to severe gastrointestinal issues in some pets or raise the risk for obesity in others, as it is easy to overfeed high-fat diets.

How to Evaluate the Raw Dog Food Evidence?

The goal of any recommendation of a given diet should be to first “do no harm.” Then the goal should be to help the subject live a longer, higher-quality life and ideally, a diet should be chosen based on sound clinical reasoning, scientific evidence and a good understanding of risk management.

Medical evidence that is available should be graded before making such decisions. To grade medical evidence, we need first to understand the different types of studies that are published on the topic of raw food diet for dogs.

Case Control Study

Firstly, a case control study identifies patients that have:

  • An outcome of interest (cases) to the study and
  • Patients without the same outcome (controls).

Then the researchers look back to check if these patients had the exposure of interest.

Case Series Study

Next we have a case series study, which consists of the examination of a series of patients with a given outcome of interest. In this type of study, there is no control group.

Cohort Study

Then there is a cohort study, which identifies two groups of patients: one that received the exposure of interest to the study and another which did not. It then follows these patient groups forward to the outcome of interest.

Randomized Controlled Clinical Trial

Then we have a randomized controlled clinical trial, which involves participants that are randomly allocated to either an experimental group or a control group. The study then follows both groups over time to examine the outcome of interest.

Meta Analysis

Finally, a meta analysis (i.e. a systematic review), develops a summary of the medical literature, using explicit methods to perform a comprehensive search of the available research and critical evaluation of individual studies. This systematic review then uses certain statistical techniques to combine the results from these studies, before grading them as evidence levels 1 to 5.

Grading Research Studies

Level 1 studies consist of systematic reviews of multiple studies, which have limited variation in their results, randomized controlled clinical trials (multiple), or a single randomized trial with narrow confidence interval (i.e. very little if any overlap between groups).

Also included in level 1 studies is the “all or none” study, in which all patients died before treatment was available, however some now survive or some died before and now all survive with the treatment.

Level 2 studies are systematic reviews of cohort studies with consistent results or individual cohort studies, including some lower-quality randomized clinical trials.

Level 3 studies consist of systematic reviews of case control studies with consistent results or individual case-control studies.

Level 4 studies are a case series or lower-quality cohort and case-control studies.

Level 5 studies include expert opinion, either without explicit critical appraisal or the conclusions are based on physiological research or principles.

Now that we have the definitions straight, let’s take a better informed look at the available scientific literature dealing with the possible benefits and risks of diets consisting of raw dog food.

Raw Dog Food’s Nutritional Benefits or Risks

There have been no published level 1, 2, or 3 studies examining the nutritional risks or benefits of raw meat feeding to dogs.

Level 4 Evidence of Nutritional Benefits

A survey study on feeding practices in the United States and Australia found that 98.7 percent of dog owners deemed their pet healthy. Among those owners, bones or raw food were provided as part of the main meal to 16.2 percent of dogs.

Less than 3 percent of owners fed their dogs exclusively home-made diets. The study did not attempt to correlate the owner’s views of health with diet, however the bone and raw food feeders would have been among the group that considered their pets to be healthy.

Level 4 Evidence of Nutritional Risks

There have been some case reports that could be classified as level 4 evidence of risk. Nutritional osteodystrophy (i.e. abnormal changes in the growth and formation of bone) was reported in two litters of six-week-old large breed puppies, which were fed a bones and raw food (BARF) diet from about three weeks of age.

Nutritional secondary hyperparathyroidism (when your parathyroid glands create too much parathyroid hormone in the bloodstream) has also been reported in a litter of German shepherd puppies, which were fed a diet of 80 percent rice with 20 percent raw meat. The diet contained excessive amounts of phosphorus. Not all puppies fed the diet exhibited problems, suggesting individual or genetic susceptibility.

A nutritional analysis of five raw food diets (two of them commercially produced and three home-made) found low levels of calcium and phosphorus in three of the five diets. The two commercial diets were high in vitamin D. Two of the diets were found to be deficient in potassium, magnesium, and zinc.

Supporters of raw diet for dogs will argue that feeding a variety of foods will lessen the risk of nutritional imbalance.

Level 5 Evidence of Nutritional Benefits

Proponents of raw food feeding have referred to a scientific article by Prochaska and Piekutowski, which supports their contention that digestive enzymes in fresh food increase biological availability and that heating depletes these enzymes, decreasing the nutritional quality of the ingested food.

The paper reviews the medical literature in support of the hypothesis that natural enzymes in food act synergistically with those in the human digestive tract, in order to release maximum thermodynamic free energy from food.

The report examines the literature, which supports the idea that the enzymes can survive the digestive process in humans and may improve the nutritional value of food. The paper then concludes that there is no direct evidence that lack of enzyme synergy leads to any disease processes.

Moreover, the paper concludes that the role of enzyme synergy has not been sufficiently studied to predict its biological significance.

Another paper looks into the long-term consumption of raw foods (not meat) in humans to assess the impact on cardiovascular disease. Raw fruit and vegetables made up 70 percent to 100 percent of the diet and it was concluded that there was a decreased risk of heart disease based on improvement in LDL cholesterol and triglyceride concentrations. However, there was possibly an increased risk of coronary artery disease because of deficiency of vitamin B12 (linked to elevated plasma homocysteine and lower HDL concentrations).

Risk of Infectious Disease to Dogs or Humans in the Same Environment

There are several studies that examine the presence of infectious agents in raw foods and the risk for contaminating or shedding these agents in the dog’s environment. One study analyzed 240 samples from 20 commercially prepared raw meat diet for dogs (beef, lamb, chicken or turkey), 24 samples from two commercial dry dog foods and 24 samples from two commercial canned foods.

The commercial foods were taken on four different dates, two months apart. Three samples were gathered from each product at each sampling point and were examined by culture for Escherichia coli, Salmonella enterica, Campylobacter and by polymerase chain reaction (PCR) for Cryptosporidium, Neospora, and Toxoplasma.

The PCR was performed only during the third and final sampling period. Close to six percent of the raw food diets were positive for Salmonella, whereas none of the conventional diets were positive.

Escherichia coli were observed in all types of diets. It was found in almost half of the raw dog food diets, but in only a third dry and eight percent canned diets. No significant association was observed between the kind of raw meat and the agents that were isolated.

In a single small study of dogs, 80 percent of raw chicken diets were culture positive for Salmonella serovars, whereas none of the commercial dry foods tested positive. Thirty percent of the stool samples of the raw chicken eaters were also positive; the commercial diet dogs’ stools were negative.

Another study looked at research dogs on a diet of frozen commercial raw food. The diet was tested for Salmonella before feeding and was divided into contaminated and non-contaminated. The contaminated diet was fed to 16 dogs and the non-contaminated one was fed to 12 dogs.

No clinical signs of disease were observed in any of the dogs, however seven of the ones fed the contaminated diet shed Salmonella serovars in their stool for 1 – 7 days after consumption. Five of the seven dogs shed the same S. serovars that was recovered from the food sample. All dogs had tested negative before the trial.

In a cohort study examining the shedding of Salmonella and other pathogens in a sample of healthy pet therapy dogs, 0.61 case / dog year of Salmonella shedding was observed in dogs consuming raw food, while 0.08 case / dog year was observed in non-raw food dogs. There was also an increased risk of shedding extended spectrum cephalosporinase producing E. coli.

Raw diet feeding is particularly prevalent in Greyhound facilities. One study examined the Salmonella serovars isolated from feces taken from greyhounds with gastroenteritis, as opposed to those isolated from the diet fed prior to the onset of diarrhea.

Out of 41 fecal samples, which were assessed, 31 tested positive for Salmonella, while 16 were the same serovar as found in the diet. For control, 35 “normal” fecal samples were obtained, of which four were positive for Salmonella.

Another observed risk is the occurrence of antimicrobial resistance in many of the isolates. A study looked into 166 commercially available raw food diets for dogs, bought randomly from local pet stores in three Canadian cities. It found a prevalence of 21 percent for Salmonella, with chicken being an ingredient in 67 percent of the positive diets. Eighteen serovars were observed with resistance present to 12 of the 16 tested antibiotics.

Few studies have observed that Salmonella shedding by dogs can result in illness in humans. A disease outbreak due to multi-drug resistant Salmonella Typhimurium has been reported in four animal facilities. Illness occurred in employees, clients, as well as animals that were present in three different companion animal facilities and one animal shelter.

Eighteen humans and 36 animals were found fecal culture-positive for Salmonella and some of the animals died. Moreover, some animals in the facilities and in the homes of clients or employees were cultured positive, but were asymptomatic.

Those affected clinically included veterinary staff, pet owners, children, as well as other pets. Although the diet fed to the pets was not discussed, the study documented that Salmonella can cause disease in pets and that humans in contact are also at risk.

Other studies have observed risk of Salmonella infections in humans linked to pig ear treats. Another paper reports a multistate outbreak of human salmonellosis linked to contaminated commercial dry dog food. This case shows that Salmonella present in a pet’s food can affect the humans in the household, with young children being at the highest risk for exposure.

Level 4 Evidence of Risk for Infectious Diseases

One paper examined 25 commercial raw food diets for dogs and cats. Coliforms were found in all diets and Salmonella in 20 percent of them.

Another study evaluated the link between feeding raw meat and Salmonella enterica infections in a greyhound breeding facility. The bacteria were isolated from 93 percent of fecal samples and 66 percent of all samples (environment, feces, food).

The examination was prompted by an outbreak of illness in the dogs associated with the feeding of raw meat that was classified as unfit for human consumption. In the ten months before the investigation, 27 puppies from eight litters had been affected, with 37 percent mortality.

Another study cultured 112 samples of commercial raw meat used in greyhound diets. Almost 45 percent of the samples were positive for Salmonella serovars and there was widespread antimicrobial resistance. However, the findings are not restricted to meat fed to greyhounds.

Salmonella serovars were isolated from 3.5 percent of the fresh ground beef samples collected from retail stores in the United States. Salmonella serovars were isolated from 20 percent of broilers, 8.7 percent of market hogs, 7.5 percent of ground beef, 44.6 percent of ground chicken and 49.9 percent of ground turkey samples from federally inspected facilities in the United States.

In a group of racing sled dogs, where diarrhea is common during racing and raw meat feeding is prevalent, Salmonella was isolated from about 63 percent of fecal samples. No significant difference was observed between dogs with diarrhea and those with normal stool.

Another paper, which examined pet dogs consuming mostly commercial foods, found an isolation rate of about 1 percent.

As the evidence strongly indicates that raw food can contain Salmonella, it is of great importance to maintain hygiene of the food preparation area and the feeding bowls. However, one study found that standard methods of cleaning and disinfecting food bowls, including soaking with bleach and cleaning in a dishwasher, were at best minimally effective at eliminating Salmonella.

Level 5 Evidence of Risk for Infectious Diseases

Raw meat diet for dogs has been cited as a human risk factor in several public health reviews. Yet, no study has conclusively documented the risk to either pets or their owners. There have been isolated case reports of illness in humans associated with Salmonella in household pets, however raw food has not been identified in these cases.

There is clearly some compelling evidence to suggest that raw food diets may be a nutritional risk. Additionally, raw food poses a substantial risk of infectious disease to the dogs, their environment, as well as the humans in the household.

It should be noted that there is no level 1 evidence from randomized controlled trials or strong level 2 evidence from sufficiently large cohort studies to examine the risks or benefits of raw meat diet for dogs. Yet, there is sufficient evidence to inform veterinarians when they discuss the human health implications of a raw diet for dogs.

Image source: Wikimedia / Sebastian Hoyer.

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