Updated: Jun 28
Weighing up the pros and cons of raw feeding to achieve the best outcome in your pets - while keeping everyone safe
We often hear of the ‘natural is best’ – the reason many chose ‘raw feeding’ is often based on this idea of back to nature and is one of the reasons for an extensively and fast-growing market in the pet food industry.
Some dogs do great on a raw meat based diet, is has numerous claimed health benefits – however actually at present there is not a huge amount of evidence to fully support this. We also need to be careful of the possible dangers and wider implications of raw feeding. If you wish to embark on this you need to be fully informed - this article aims to investigate this more.
Social media and the internet have undoubtedly played a role in the spread of misinformation. As veterinary professionals it has become increasingly obvious in recent years that many people are becoming interested in feeding raw meat based or Bone and Raw Food (BARF) style diets for their animals – so weighting up the pros and cons are required.
A sad and unavoidable corollary to this mantra is that processed diets harm pets’ health. Many proponents of the diet use a number of reasons for it being superior to commercial processed diets, some of them unsubstantiated. One common theme is the idea of reverting back to our dogs’ ancestral diet as wolves would have eaten. Investigations into this theory are necessary to ensure we remain objective in our assessment of the appropriateness of these diets when used in a companion animal setting.
Are dogs’ wolves?
A survey on motivation behind raw feeding found that 26% of respondents said ‘to respect the dog’s carnivorous nature’ when asked to indicate the main reason they chose to provide raw meat-based diets.
The domestication of the dog we know and love today started some 27,000 and 40,000 years ago with genetic evidence suggesting that dogs split from their wolf ancestors between these periods. Theories of domestication still vary however it has been suggested that it was originally due to food surplus encouraging wolves to move closer to human settlements and become accustomed to the close contact whereas other theories suggest they were encouraged and utilised as hunting aids.
Dogs’ ancestor, the grey wolf, is not an obligate carnivore and some wolf populations eat much plant matter when seasonally available. Over many thousands of generations dogs evolved away from the wolf’s ‘top predator’ ecological niche and adapted to the niche of omnivorous scavenger commensal on humans as a mutually beneficial relationship. Dogs, including the worlds’ free-roaming 'village dogs', similar to the ancestral dogs from which modern breeds were derived, have a very different phenotype to wolves; differing in anatomy, physiology, reproductive strategy, cognition, behaviour including food acquisition strategies, gut microbiota and diet.
Our pet dogs are not actually direct descendents of the grey wolf we have today; they are distant cousins sharing that common ancestor. In the process of domestication gene expression has changed. The original wolf (and grey wolves today) have a limited (but not negative) ability to digest grains, whereas the domestic dog produces the digestive enzyme amylase in more than adequate qualities to fully break down carbohydrate sources and extract the nutrition they contain. Specifically interesting is dogs’ ability to digest starch. A team of Swedish researchers compared the genomes of wolves and dogs and found a big difference between the two is a dog's ability to easily digest starch.
Even after removing obviously harmful natural factors, e.g., parasites and other pathogens, it is unlikely that a species’ evolutionary diet will be the optimal diet we want for our pets. Many wild species have sub-optimal diets due to issues in supply, acquisition or predation of their plant or prey diet. Numerous examples exist of species’ evolutionary diets being sub-optimal for example, the high rate of tooth fractures in wild carnivorans. A wild species’ evolutionary diet is adequate for each species to produce as many offspring as they do, by definition sufficient for survival of the species, but not optimal for individual animals’ welfare and lifespan – but it is the latter we want for our pets: most wild carnivores die before they get old.
Anecdotal benefits for the diet include improvement in coat and skin; elimination of breath, body, and faecal odour; improvement in energy, behaviour, and immunity; and a reduction in medical conditions including allergies, arthritis, pancreatitis, dental disease, and parasitism: these potential health benefits have not undergone thorough scientific evaluation yet (Freeman et al. 2013).
Possible benefit for uroliths
Investigators in a study found indications of lower calcium excretion in urine of dogs eating a commercial raw diet, compared with excretion in dogs eating a commercial dry extruded diet. This could indicate it may be beneficial for dogs prone to calcium oxalate urolithiasis. However, the raw diet contained considerably more water than the dry extruded diet, so it is difficult to interpret the importance of these results - it did not compare against a veterinary ‘prescription’ urinary diet or wet diet: further research is required in this area.
A common benefit stated by proponents of raw food feeding is in reference to digestibility and bioavailability of raw feeding. Studies have documented high digestibility of raw meat diets fed to exotic and domestic carnivores. This increase in digestibility could result in decreased feed intake and faecal output aiding in overall management and husbandry which is very positive.
Processing meats, with use of heat for example, can actually increase bioavailability of proteins through collagen breakdown and an increase in exposure to an animal's digestive enzymes, but it also can negatively affect amino acids in some instances. One study concluded that ‘although there is evidence for improved digestibility of proteins in raw meat-based diets, compared with digestibility of proteins in extruded diets, the clinical effects of this difference are unclear and require further study.’
It is also suggested that digestive enzymes in fresh food enhance biological availability and that heating (either by cooking or in the processing of commercial diets) depletes these enzymes and therefore the reduces the nutritional quality of the ingested food e.g., cooking or processing in anyway reduces the nutritional value. The theory in one human study hypothesised that vital enzymes in ingested food interact synergistically with enzymes within the human body and more specifically with enzymes in the digestive tract. It was suggested that alterations in food enzymes induced by processing such as heating, irradiation and the addition of chemical additives have been proposed to create a decrease in metabolic availability of nutrients, with the long-term consequence being disease. Along the same line as this hypothesis, upsettingly some claim that commercial dry/wet diets cause illnesses, and believe that vets are promoting these diets to make more money - this is unsubstantiated. It was concluded in this particular study that there is no direct evidence that lack of enzyme synergy leads to any disease processes and that the role of enzyme synergy has not been studied in sufficient detail to predict its biological significance.
So, while digestibility may be a positive in raw diets – this does not mean that commercial cooked / processed are bad.
Another demonstrated health benefit is that raw bones given as chews reduce calculus – as do other hard/abrasive chews. This is a positive finding as many dogs in the UK suffer from dental disease. Chewing is also very stimulating behaviour for many dogs and is really positive behaviour for them.
However, this study has not yet been followed by an assessment of dental health at sub gingival (below the gum line) level, which is more appropriate when examining true dental health in dogs such as the use of dental X-Rays and examination under general anaesthesia. Furthermore, many commercial raw diets do not include intact bone - these may be given by people feeding a raw diet as additional supplement. There is concern that chewing bones, particularly weight-bearing bones such as knuckle bones, increases painful tooth fractures - veterinary dentists do not recommend using them for this reason. If bones of inappropriate shape and size are given we also have a risk of gastrointestinal issues such as foreign body obstruction or GI perforation .
The reduction of calculus does not translate into reduced periodontal disease – indeed, wild canids and felids, and feral cats, eating wild prey have high rates of tooth fractures and periodontal disease. Wild carnivorans have a high rate of tooth fractures that, across species, correlates with the amount of hard material, e.g., bone, in their diet. A study in foxhounds fed raw carcasses, including raw bones, showed that they had a high prevalence of tooth fractures, the skulls of African wild dogs eating a “natural diet”, also showed evidence of teeth wearing (83%) and fractured teeth (48%) and free-ranging maned wolves in Brazil on oral examination revealed crown fractures.
It has been concluded that considering the weak evidence on raw bones and lack of evidence on other types of raw treats, veterinarians and veterinary nurses should be cautious when recommending raw treats to support periodontal health in dogs.
Overall, one review by Davies et al (2019) stated:
Claims for improved oral health in diets with raw bones find support in studies showing less calculus among feral or wild dogs and cats yet, on balance, the limited published evidence does not support claims of reduced periodontal disease with raw feeding.
Concerningly in a survey about raw feeding only 1% of owners acknowledged the possibility of health risks associated with this kind of diet. Any diet, whether raw or dry, has both beneficial and harmful effects. The important consideration is weighting up the benefits against the risks and analysing the evidence to ensure we are not putting our pet or ourselves and others at risk.
Health risks associated with raw diets include various diseases resulting from nutritional deficiencies or toxicities; as afore mentioned the vast majority of home prepared raw diets fail to meet nutritional standards. This is why it is essential to use a board-certified veterinary nutritionist to guide your recipes if you choose to home prepare.
Moreover, dogs and cats, raw-fed or not, carry zoonotic (germs which can spread from animals to humans) pathogens, and raw feeding increases carriage of zoonotic and potentially antibiotic-resistant bacteria. Importantly, freezing raw meat may not kill all of these bacteria, and the risk is not fully mitigated by food-preparation hygiene measures because some bacteria colonise raw-fed pets, which shed them around the home. These organisms do not always make pets ill, they may become "asymptomatic carriers", meaning they can spread bacteria which are harmful to humans without showing any signs. There are published reports of bacterial illness and fatality in pets and humans associated with raw-fed pets. Studies have not yet been done to determine to what extent raw feeding pets increases human or pet morbidity, disease and mortality however so we do need more evidence of this in future to determine significance.
Although many believe that good hygiene practices will mitigate these issues this may be hard to achieve. A study found that standard methods of cleaning and disinfecting food bowls were minimally effective at eliminating Salmonella: this included soaking with bleach and cleaning in a dishwasher.
Several government and veterinary agencies have issued statements regarding raw food and concerns over public health citing:
Feeding pets raw foods is not in agreement with their goal of protecting the public from significant health risks
That they discourage feeding raw foods to dogs and cats because of salmonellosis risk and other infections to both pets and owners
Cautioned regarding the health risks associated with raw feeding and recommended clients work with their veterinary surgeon to determine if feeding a raw diet is the most appropriate choice
Microbial contamination, by either bacteria or viruses, is the most frequently documented disadvantage of feeding raw feeding. Specifically, Salmonella spp has received the most attention; however, other pathogenic bacterial contaminants include Escherichia coli, Listeria, Clostridium, and Campylobacter spp. Other worrying contaminants include tuberculosis infections in cats.
Dogs possess some physiological adaptations that may allow them to tolerate relatively high levels of microorganisms in their diet and may not frequently exhibit clinical illness when colonised by potentially pathogenic bacteria. However, it has been documented that dogs have experienced clinical illness with raw food associated pathogenic infection. Concerns also lie in the zoonotic risk to people, most notably children, elderly or the immuno-compromised members of society who may be at increased risk. Owners should consider this risk carefully if their raw-fed pet ever has contact with anyone in these groups, even if the animal appears healthy.
Parasites and Protozoa
Another zoonotic concern includes Echinococcus (hopefully not in the UK!); a Hydatid tape worm dogs can pick up if they are fed raw carcass meat and offal. Concerningly, it has been attributed to a rise in human alveolar echinococcosis cases in Canada. Alveolar echinococcosis is a zoonotic cestode infection which is usually fatal in the absence of treatment. In one small study of human alveolar echinococcosis, 82% had kept dogs. Although no link has yet been proven it is thought the rise is due to the urbanisation of coyotes in the area and is an area we need more studies into.
Other parasites and protozoa associated with raw carcass includes taenia, neospora caninum, sarcocystis and toxoplasma gondii. These parasites and protozoa have implications for our food chain and livestock – so vigilantly picking up faeces and rigorous and regular worming with prescription worming products is of vital importance. These are mainly caught via carcass ingestion, so if your dog is a scavenger on walks - whether raw fed or not - we must follow these recommendations.
According to the Centers for Disease Control and Prevention (CDC) “antibiotic resistance is one of the biggest public health challenges of our time.” This is concurred by the World Health Organization (WHO) that describes antibiotic resistance as “one of the biggest threats to global health, food security, and development today.”
Concerningly in on study looking into raw-frozen samples they found that they all carried bacteria that are resistant to many antibiotics, including standard antibiotics that healthcare professionals prescribe regularly.
The authors of the study stated that, “the close contact of pets with humans and the commercialization of the studied brands in different EU countries pose an international public health risk if transmission of such strains occurs between dogs and humans.”
Homemade V Commercial
Interestingly a study into homemade diets in dogs found them to be rarely balanced leading veterinary professionals to worry about the short and long-term implications this diet may have on companion animals’ health. Although ‘home-made’ doesn’t necessary correlate with ‘raw feeding’ as there are commercial brands available a percentage of raw feeders do make their own formulations at home – so using a board-certified veterinary nutritionist to support you is essential. Many online recipes are not balanced. Once study by Pedrinelli et al stated:
A large percentage of nutritional imbalances was verified in the recipes investigated in the present study, exposing dogs and cats fed them to nutritional problems, compromising health and longevity.
Many dogs do well – but care must be taken
Although of course it is possible to create a raw diet for dogs that is nutritionally balanced for their needs it should be based on modern nutritional science and knowledge and the optimal diet might actually be surprisingly far-removed from the ‘natural’ diet of the forebears. Risks exist, and it's important that they aren't understated, or dismissed without proper consideration. As with any dog diet – not all commercial raw foods are made equal so talking to a board-certified veterinary nutritionist, veterinary professional or looking into a Pet Food Manufacturers Association (PFMA) registered brands can help to guide your decision.
Many dogs do well on raw – but this does not mean we should dismiss the wider issues associated with it. If raw feeding is undertaken lightly, it can not only have implications for your pets but also for your family, the public and the food chain too.
There are many benefits perceived by advocates, and some dogs do exceptionally well on raw feeding, experiencing minimal issues – this is really positive. However, feeding raw diet does carry risks – we really must take care. Weighing up the benefits against the risks should be part of choosing any pet's diet, because the health of our animals and our human families is of the utmost importance.
Author: Robyn J Lowe BSc Hons, Dip AVN (Small Animal), Dip HE CVN, RVN
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