Feeding for health and longevity: Raw vs. kibble vs. calories

In May last year I changed the dogs' teatime meal to a commercially prepared, 'ready-made' raw food diet.  At the time and for a long time beforehand, I believed that raw was the best way to feed a dog, but six months down the line, the diet wasn't working out well for Tilly.  I had to stop and re-evaluate my thoughts about raw feeding being the healthy option, and question what the domestic dog's 'species-appropriate' diet really should be. 

Dogs are carnivores, there is no doubting this, but carnivores fall into different types.  There are true or ‘obligate carnivores’ – animals that depend solely on the nutrients found in animal matter for their survival.  While they may consume small amounts of plant matter, they lack the physiology required for the efficient digestion of plants.  All felids including the domestic cat are obligate carnivores, requiring a diet consisting of primarily animal flesh, bones and organs. 

Dogs and other canids are ‘facultative carnivores’.  ‘Facultative’ means contingent, optional, or not required – in other words, while the primary diet of dogs is meat, dogs are actually capable of surviving without it.  Studies of the wolves of Yellowstone National Park in the USA reveal that even when prey animals are in plentiful supply, on average, the wolves only eat fresh prey every 2-3 days.  This can drop to only a few times per month during the winter, with the rest of the diet being made up of carrion (sometimes only frozen hide and bones) and whatever pickable, edible vegetation happens to be available.  In the wild, wolves don’t eat much, not even much of their primary food – fresh, raw prey – and they will go for days without eating anything at all. 

Dogs are also scavenger carnivores, meaning that although the meat that they would naturally consume may well be raw, it may not necessarily be fresh.  The decomposing flesh of carrion is in essence partly digested, with bacteria having already done some of the ‘eating’.

Being a carnivore, the dog’s dentition is geared towards a diet of flesh and bone.  Each side of an adult dog's upper jaw has 3 incisor teeth, 1 large canine tooth, 4 premolars and 2 molar teeth, and the lower jaw has 3 incisors, 1 canine tooth, 4 premolar and 3 molar teeth. 

The number and types of teeth reflect those of a ‘mesocarnivore’.  The earliest Carnivora family of Miacidae, of which Miacis, the earliest known ancestor of the domestic dog was a member, were mesocarnivores.  Modern day mesocarnivores include wolves, coyotes, foxes, civets and skunks, as well as dogs. 

Beyond the teeth, the dog’s gastro-intestinal system is that of a carnivore, being much shorter in proportion and in comparison with the GI tracts of herbivores.  The overall length of the canine GI tract (from mouth to anus) is about 5 times the dog’s total body length, whereas the length of the herbivorous equine GI tract is about 15 times the horse’s total body length.  The human GI tract is 10 times longer than the length of the body. 

The natural diet of a mesocarnivore would ideally consist of 50-70% animal and 30-50% plant matter.  In comparison, the diet of ‘hypercarnivores’ (e.g. cats, eagles, sharks, salmon) consists of more than 70% animal, and that of ‘hyopcarnivores’ (e.g. Black bear, raccoon) less than 30% animal.  While virtually all animals display omnivorous feeding behaviour according to conditions such as food supply, etc, animals generally prefer one class of food or another, for which their digestive processes are optimised accordingly.  The classification ‘omnivore’ refers to the adaptations and main food source of a species in general.  The main food source of an omnivore is variety in itself – pigs for example are true omnivores – but a plant-eating carnivore or a meat-eating herbivore is neither individually nor as a whole species omnivorous.  It may surprise you to learn that humans are not omnivores either, and neither are we carnivores or herbivores.  Like all of our primate ‘cousins’ we actually belong to a class of plant-eaters called ‘frugivores’, or fruit-eaters.  Just as carnivores can and do eat plant matter, frugivores (also herbivores, nectarivores, florivores and granivores) can and do eat meat.  The dog is a facultative carnivore, a scavenger carnivore and a mesocarnivore, NOT an omnivore. 

Being a mesocarnivore, the dog’s diet would ideally consist of 30-50% plant matter, but unlike herbivores, dogs lack the bacteria in their gut that produce the enzyme ‘cellulase’ and therefore the ability to break down cellulose – the major component in the rigid cell walls in plants.  Certainly, when some cellulose-rich foods are fed, they are still intact and recognisable within the dog’s faeces, for example, sweetcorn kernels, and grass (as anyone who has had the displeasure of removing grass-dangley-poops from their dog’s bottom will know).  For herbivores, the result of the digestion of cellulose is glucose, which is how they obtain their energy.

Dogs also lack the salivary enzyme ‘amylase’ needed to digest starchy plant matter found in cereals, grains and fibrous vegetables.  Coupled with the fact that dogs also lack grinding molars, the lack of salivary amylase is often used to uphold the theory that dogs are carnivores and therefore should not be fed plant matter at all, however, grinding molars and amylase are not needed for the digestion of ‘softer’ plant material composed mainly of water and simple sugars, such as fruit.  What is also often omitted in the ‘Prey Model’ of feeding is that although dogs lack salivary amylase, amylase is produced in the pancreas, so the digestion of starch-rich plant matter is possible once this has passed into the dog’s small intestine.

Contrary to popular belief, wolves do not eat the stomach contents of large, herbivorous prey animals.  Stomach acid is highly corrosive and would burn the mouth and oesophagus if eaten (and also corrode tooth enamel).  Occasionally, wolves will eat the stomach wall of large herbivorous prey animals, but only after shaking out the stomach contents.  The stomach contents of smaller prey animals such as rabbits, mice and birds is eaten, but only as a result of the entire animal being consumed – claws, fur, beak, feathers and all.

So … based on the domestic dog’s carnivore types (facultative, scavenger and mesocarnivore) and given its likely evolutionary route and self-domestication from the small Asiatic (Arabian) wolf, it could be concluded that the most ideal, most natural, most appropriate doggy diet ideally should consist of 50-70% small, raw, whole prey (flesh, bones, organs, fur, feathers, etc) including mammals, birds (and their eggs), reptiles and invertebrates such as worms and insects, and scavenged carrion (this could include fish and large animals), and a 30-50% mix of the stomach/intestinal contents of small herbivorous and omnivorous prey (e.g. rabbits, squirrels, mice, birds), ripe fruits and berries and various other ‘pickable’ plants and botanicals.  However, the latest DNA evidence suggests that the dog began to branch away from the wolf between 100,000 and 135,000 years ago.  We also know that around 15,000 years ago, at the end of the last ice-age, dogs became the domesticated canines that we know and love today.  During this time, and particularly so during the past 3,000 years of intentional, selective breeding, numerous anatomical and behavioural changes have taken place as a direct result of the domestic dog’s strategy of life, to stay near humans for the best chance of survival (which includes eating our food). 

The dog has not been a wolf for many thousands of years, and numerous features of the dog’s anatomy including skull, teeth, skeleton and GI tract differ significantly from those of wolves both of the past, and of the present.  This means that according to the domestic dog’s strategy of life – to stay near humans for the best chance of survival – the 50-70% animal part of the ‘dog as mesocarnivore’ diet should also include table scraps such as cooked meat and dairy (milk, yoghurt, cheese, etc) and the non-animal part, raw, cooked and partially cooked vegetables, cereals and grains, as well as a smorgasbord of excreted poop from humans and the local domestic and wild animal populations.  This gives a whole new perspective on ‘natural feeding’, and one that implies that popular raw diet formulae such as Prey Model, Natural Raw Diet, Raw Meaty Bones and BARF (Bones and Raw Food, Biologically Appropriate Raw Food) are all flawed in some way or another. 

What to feed is a personal choice that we make for our dogs based on what we believe to be the best.  There is no scientific research to support the claimed, nutritional benefits of raw feeding, only anecdotes and testimonials, however, there is scientific evidence to the contrary both in nutritional analysis studies of raw food diets for dogs and in veterinary case studies of cats and adult dogs and puppies fed various raw diet formulae.  Certainly in six months of feeding a commercially prepared, 'ready made' raw food diet to my dogs, both of whom were in great, general health to begin with anyway, I have seen no obvious beneficial health changes but instead the opposite, when throughout October and November Tilly began to suffer worsening, nightly abdominal discomfort that upon switching her back to her breakfast kibble (Acana) for her teatime meal, ceased completely.  Wanting to ensure that she was back to good health I had her blood tested, and although symptom-free at the time of these tests, she tested positive for pancreatitis.  Two months on since stopping the raw food and her blood lipase level is still double the norm, but I'm hoping that this will continue to drop now that I have switched her onto a bland, low-fat wet food (Chappie).  I am very thankful that my dogs sleep next to my bed, otherwise I would be none-the-wiser to her nightly discomfort and the seriousness of what was developing.  I am also thankful that I am not so far up my own bottom not to be able to change my long-held belief that raw just has to best, or to delude myself that Tilly's symptoms of digestive upset after 6 months of raw feeding must either be normal, or due to something other than the food.  However, I have seen the apparent health benefits of raw feeding in a client dog who had a multitude of infected tick bites on its head that despite several months of antibiotic treatment had failed to clear up.  After only four days on a raw food diet, the tick bites were no longer infected, and a fortnight later there was no evidence that the bites had ever been there.  I don’t think that this was coincidence and I do think that the healing was directly connected to nutrition.  Protein is needed for cell development and repair.  Amino acids are the building blocks of proteins.  Amino acids are critical to life and have many functions in metabolism.  Some protein sources contain higher levels of certain amino acids than do others, and some protein sources contain a broader range of amino acids than do others.  Cooking alters the molecular structure of protein, which may make assimilation difficult, and the cheaper commercial kibbles use lower quality protein sources in their formulae.  Before switching to a raw food diet the dog was being fed what I consider to be a low quality kibble (high in cereal, low in meat, and a minimum level of vitamin D).  I think that the raw food gave him a much needed protein and vitamin D super-boost, which finally enabled his body to repair the damage, and quickly too.  Many of the raw feeding anecdotes are along similar lines – "dog with chronic illness gets well when fed a raw food diet".  Maybe it would be more appropriate to use raw feeding as medicine for dogs, not as the primary diet, and like any course of medicine to stop giving it once the illness has been cured.  

And perhaps there is nothing wrong with long-term raw feeding if the nutrition truly is balanced, complete, and doesn't contain excessive amounts of fat, however, laboratory analyses of five raw diets including two that are commercially produced have shown up nutritional shortfalls in a wide range of minerals including iron, zinc, potassium, manganese, calcium and phosphorous, as well as vitamin E, and nutritional excesses including vitamin D and magnesium.  Similarly, whether homemade, canned or kibbled, there is nothing wrong with feeding a cooked diet that is nutritionally balanced and complete (according to AAFCO) and includes a small proportion of cereal or grain.  But whatever the diet, quality of the ingredients is important, and by quality I mean ‘additive free’.  Many raw-fed dogs are fed fatty, domestically raised animals that have been pumped full antibiotics, hormones and vaccines, and while raw animal flesh, bone and organs are worthy of inclusion into the dog’s diet, feeding fatty, ‘adulterated’ raw meat really is not the healthy option.  Feeding a raw diet that does not consist of between 30-50% digestible plant matter is, in my opinion, not dog-appropriate, and the practise of supplementing a raw or home-cooked diet with probiotic bacteria, digestive enzymes and/or vitamin/mineral/amino-acid rich ‘super-foods’ when the nutritional content of the diet itself has not been thoroughly analysed, is questionable both in benefit and ‘appropriateness’.

Adding supplements also suggests that the dog can’t get enough nutrition from a raw-food diet.  ‘Ah but …’ say many raw-feeders, ‘… in the wild, dogs and wolves would eat all of the carcass, so the nutrition would be balanced and complete.’  So disregarding the fact that dogs are not wolves and have not been living ‘in the wild’ for a very long time, let me get this right – the eating of the ‘non-meat’ parts of a raw carcass makes a meal balanced and complete, but commercially produced pet foods that may contain these ‘derivative’ parts (e.g. hair, hooves, feathers, beaks, sinews, tracheae, guts, eyes, snouts, bum-holes, etc) should be avoided like the plague because they are inferior, junk ingredients?  The fact is that predators will selectively eat for nutritional value, for the best balance of protein, fat and other nutrients, but this has nothing to do with eating an entire carcass, it has to do with having a much, much wider menu from which to self-select.  Self-selection as well as a huge variety of different foods is what today's feeding practices lack, regardless of whether or not the food given is raw or whole.  The dog's choice of what to eat, how much to eat, and when to eat it, is limited.  We decide for them.  The dog's natural feeding practice is 'buffet-style', but we take away this choice to feed naturally.  We prohibit the dog's natural inclination to self-select for balanced nutrition.    

I’m not suggesting that all kibbles are nutritionally 'complete'.  They may be complete as per AAFCO standards and balanced in the nutritients that they actually contain as in there are no excesses or no deficiencies of those ingredients, but some may be lacking in certain vitamins, protein amino-acids and nutrients essential for optimum health simply because there is no legal requirement for pet food manufacturers to include them, or they are included at minimum levels that aren’t sufficient for some dogs to remain in gleaming health (e.g. those with digestion or assimilation problems or chronic illness).  But at least the commercial kibbles aren’t pretending to be something that they are not, and supplementing a commercial kibble diet with a weekly portion of oily fish, the occasional whole, raw egg, a raw, lean, meaty lamb rib (as a meal replacement), a carrot, a broccoli stalk, a handful of blueberries or a few mg of ‘super-greens’ now and again is more likely to enhance overall nutrition than unbalance it.  Incidentally, the past and present feeding practices of captive wolves show that they live longer and remain healthier when fed commercial dog food.  No word of a lie.  According to the leading specialists in wolf husbandry and medicine, feeding commercial dog food, not raw prey, is the recommended practice.  To provide enrichment for the wolves and bait for husbandry purposes raw meat and bones are fed, but not as the main diet. 

But whatever diet choice we make for our dogs, whether that be raw or cooked, commercially produced or home prepared, fresh on the bone, canned, pouched or kibbled, expensive or cheap, one thing is absolutely certain - overfeeding reduces lifespan.  Overfeeding is perhaps the biggest error that pet owners make – even those who feed to manufacturers’ recommended guidelines and according to ‘ideal’ breed weight.  More than 60 years of scientific research shows us that calorie restriction is the only nutritional intervention that consistently extends the lifespan of animals.  For example, in a controlled study of 48 Labradors, feeding 25% less food than the calorie requirement for ideal body weight saw an average lifespan increase of around 2 years.  In addition, compared to the control dogs who were fed to maintain ‘ideal’ body weight, the food restricted dogs weighed less, had lower body fat content, lower serum triglycerides, triiodothyronine, insulin and glucose concentrations, and the onset of the signs of chronic disease was delayed.

Calculating the ideal daily energy requirement for a dog is a little complicated, but not difficult.  First, we need to know the dog’s ‘ideal’ weight.  The standard guideline is to be able to easily feel the ribs beneath the coat, see a definite waist when viewed from above, and an abdominal tuck when viewed from the side.  We also need to know the Metabolic Energy value (kcal/kg) of the food that we feed.  This information is usually easy to find on the packet label of commercially produced, complete kibbles and some canned and pouched foods.  The final piece of information that we need to calculate daily energy requirement is the dog’s age, sexual status and activity level.  Tilly’s ‘ideal’ weight by eye and feel is around 14 kg.  She is between 5 and 7 years old, spayed, and typically active. 

According to the dog food calculator (picture left), this gives me two category choices – ‘typical’ and ‘senior, neutered, inactive’.  She is neutered, but she is neither senior nor inactive, so ‘typical’ more accurately describes her. 

I feed her Chappie original canned, which has a Metabolic Energy value of 850 kcal/kg.  The resulting calculation is that she requires 796 calories per day and I should be feeding her 940 grams of Chappie per day, however, to follow the 25% food restriction diet to increase lifespan, a further calculation is needed. 

To calculate 25% of 796, we need to divide 796 by 100 (7.96) and then multiply this by 25 (199).  This gives a reduced daily calorie intake of 597 (796 – 199). 

We know that 940 grams contains 796 calories, so to reduce this by 25% we divide 940 grams by 100, which gives 9.4 grams (1% of 940 grams), and then multiply 9.4 grams by 25 to give 235 grams.  940 grams minus 235 grams is 705 grams.  So actually, Tilly requires 705 grams of Chappie per day. 

Beau’s ‘ideal’ weight by eye and feel is 32 kg.  He’s 3 years old, neutered, and very lazy, so even though he’s a young dog, I place him in the ‘senior, neutered, inactive’ category.  I feed him Acana Grasslands kibble, which has a Metabolic Energy value of 3750 kcal/kg.  According to the dog food calculator, this works out at 1211 calories and 320 grams of Acana Grasslands per day.  To feed for increased lifespan, this is reduced to 908 calories and 240 grams of Acana Grasslands per day.  If I went by Acana’s daily recommendation for an inactive, 32 kg dog, I would be feeding him 320 grams per day – 80 grams more than is needed.  Beau’s ‘feeding for increased lifespan’ weight is around 31 kg.  Feeding for increased lifespan drops the ‘ideal’ weight by 1 kilo – that’s a whole kilo of excess fat!  Visually, the difference in my dogs between ‘ideal’ and ‘increased lifespan’ weights is that the ribcage is more defined, with the outline of the last three ribs visible beneath the coat (picture right).

  

It is much, much harder to calculate how much raw food to feed because meats, vegetables, plants, etc, differ greatly in their individual Metabolic Energy values.  The general guide to feeding raw food is around 2% of the dog’s ideal body weight per day.  For Tilly this works out at 300 grams per day in which to pack 796 calories (her ‘ideal’ weight calorie count).  To feed for increased lifespan, we need to reduce the calories to 597, but to feed for variety, the quantity of food fed per day will fluctuate greatly in order to provide the correct calorie count per meal.  For example, there are around 85 calories in 100 g of raw tripe, which means that an all tripe day for Tilly weighs in at 705 g, but if fed according to the 2% rule would provide her with a meagre 238 calories.  Raw lamb ribs are around 284 kcal per 100g, so an all lamb rib day for Tilly weighs in at 210 g, but feeding lamb ribs according to the 2% rule would provide her with 796 calories (and a huge quantity of fat).  Because the Metabolic Energy values of different foods is so inconsistent, realistically, the best way to feed a raw food or home-cooked diet is by calorie content, not by weight, whilst trying to keep the overall quantity of the meal at around 2% of the dog’s bodyweight.  That way, meals that combine meat, bone, offal, fish, egg, dairy and veg, fruit, grain, cereal, herbs based on the mesocarnivore 50-70:30-50 animal:plant ratio of the human-food-eating domestic dog could be made without overloading or starving the body with such wildly fluctuating daily calorie intakes and meal weights, although the ratios per meal would need to differ from dog to dog to accommodate individual calorie needs.      

But calories are only a part of the story.  Even if increased lifespan calorie counts for an individual dog can be achieved at around 2% of bodyweight per meal formula per day, the levels of protein, fat, vitamins and minerals will continue to remain inconsistent across each meal.  This could have three possible outcomes:

1. over time the inconsistencies balance themselves out
2. over time the inconsistencies saturate the body’s organs and tissues with excess waste (toxaemia)
3. over time the inconsistencies leave the body deficient in some way (malnourishment)

It’s tricky enough even with all the right information to get the long-term balance right with a home-prepared diet, and while it may be safe to assume that the producers of commercial ‘complete’ raw food diets have taken care of this for us, the full nutritional content with nutrient levels, along with Metabolic Energy values, are unavailable.  Some list the % values for moisture, protein, fat, ash and fibre.  Some also list vitamin, mineral and amino-acid content, but none list the levels of these nutrients and so do not provide enough information to know for sure that according to the 2% rule (or thereabouts) the food contains a complete and balanced compliment of vitamins, minerals and other essential nutrients.  If feeding only one meal variety that contains just one meat source (e.g. chicken only) and the same vegetable/fruit/‘other’ combination and meat:plant ratio as other meal varieties, this WILL give rise to nutritional deficiency or excess over time, unless the formula has been adjusted accordingly for balance (which to my knowledge, none have).  Even feeding a range of meal varieties is no guarantee of balance because they each tend to be made to the same meat:plant ratio and the same combination of 'plant', with the type of meat being the only element that changes.

My own journey into raw feeding has turned out to be nothing more than a detour, and even though I truly believed that raw was the best way to feed my dogs and to some extent still do, somewhat of a learning curve too.  I’m neither for raw nor against it, but until the commercial, ready-made raw food diet producers can supply complete and balanced nutrition along with full analyses and Metabolic Energy values of their meals and they can achieve this with a fat content of 4% or lower, I will continue to feed Chappie (Tilly) and Acana (Beau) as the primary diet – with the occasional added extra (fish fillet, handful of blueberries, chunk of apple, etc) for variety and to boost basic nutrition. 

I want my dogs to remain healthy and to live as long as possible, and the scientific evidence shows that reducing the daily calories of a commercially produced, complete and balanced kibble by 25%  allows for an average increased lifespan of two years.  Quality and appropriateness of ingredients is important.  Complete and balanced nutrition is also important – but ultimately, it’s reducing the calories that counts in the longevity stakes. 

Less really does mean more – more years, and better health for longer. 

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Bibliography & Resources

Wolves: Behavior, Ecology, and Conservation.
L. David Mech and Luigi Boitani.

Canine Behavior: A Guide for Veterinarians.
Bonnie V. Beaver.

The domestic dog: Its evolution, behaviour and interactions with people.
J Serpell.

Dog Food Calculator
Mike Sagman.

Dog Food Advisor: Saving Good Dogs from Bad Food.

Nutritional analysis of 5 types of “Raw Food Diets.”

L. Freeman, K. Michel.

Journal of the American Veterinary Medical Association 2001;218(5):705. 

Raw food diets in companion animals: A critical review.

Daniel P. Schlesinger, Daniel J. Joffe.

Effects of diet restriction on life span and age-related changes in dogs.

Richard D. Kealy, PhD; Dennis F. Lawler, DVM; Joan M. Ballam, MS; Sandra L. Mantz; Darryl N. Biery, DVM, DACVR; Elizabeth H. Greeley, PhD; George Lust, PhD; Mariangela Segre, DSc; Gail K. Smith, DVM, PhD, DACVS; Howard D. Stowe, DVM, PhD.

Science-based medicine ~ “Raw Meat and Bone Diets for Dogs: It’s Enough to Make You BARF”. 

Dr Brennan McKenzie, MA, VMD.

Predators Hunt for a Balanced Diet
Science Daily

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Tilly update, 10th February ~ Re-test for cPL has confirmed that finally, this has decreased to a normal level again.  The bad news is that proximal inflammation/damage to her small intestine as a result of the pancreatitis has left her with a folate (vitamin B9) deficiency, so I am working to increase this via dietary supplementation.  I will be re-testing cPL and folate levels again in a month's time to see whether we have continued, normal cPL, and an increase in folate.