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Omnivore or Carnivore?

Does your dog need fruits and veggies?

By: Emily Hendren

As you begin your raw feeding journey and research you may end up reaching a few forks in the road. One of those being feeding fruit and veggies is a necessity and the other that they’re not needed in the diet at all.  Being a Prey Model site we lean towards the latter and this article will explain why.

First, let’s discuss the anatomy and physiology of a domestic dog. What we know to date is that dogs evolved from wolves and to this day share 99.9% DNA with them. According to the physiology experts all that time and evolution did not change who they are on the inside.(1,2,3,4,5) 

The Head & Mouth:

Look at their mouth, they don’t have large flat molars needed to grind plant matter like an omnivore or an herbivore does, instead they have pointed and jagged teeth meant to rip and tear flesh and crunch bones as well(1,5,6,7,8). Dogs have no salivary amylase(2,4,9) either which is an enzyme that aids in breaking down the cellular wall of plants and without that enzyme it’s left up to the enzymes in the pancreas to break those cells walls down.

Dogs have a taste system that is predominantly that of a carnivore. The presence of both amino acids and nucleotides sensitive receptors indicates they’re able to detect compounds found only in raw meat and carcass(6,10). They also have salt specific taste buds which reflects the carnivorous diet that is salt balanced(6). All of this pointing to them having the smell and taste for meat above other things.(11,12,13,14)

The Digestive System:

 Unlike omnivores, dogs have highly elastic, highly acidic stomachs with short and fast intestinal tracts and undeveloped caecum(2,3,4). They have dominant bacteria found within their gut (Bacteroides, Clostridium, Lactobacillus, Bifidobacterium and Enterobacteriaceae) which are adapted to meat digestion(15). During digestion a dogs stomach acid can reach a pH below 1.0 (equivalent to battery acid) and will hold a meal longer in order to pulverize it more. However, once the stomach is emptied the transit time is rapid. On average a dog's gut contracts around 5.2 times per minute. They’re literal pulverising machines! All of this combined, a dog's gut is ill-equipped and unprepared for raw plant digestion.(16,17,18,19,) 

What about the recent studies that show dogs have developed more copies of the AMY2B gene than wolves? This is a fact. However, the number of these genes is still small and differs between breeds ranging between only 3 copies to 32 all depending on their exposure to carbs and humans over time. But, this gene doesn’t just differ in dogs. Interestingly enough the AMY gene differs in humans and other mammals as well. (20.21)

More Interesting Facts

It was once believed that wolves and even wild dogs would eat the stomach contents of their prey. This assumption that they need fruits and veggies because of the stomach contents has been debunked by many sources. 

In the book ‘Wolves: Behavior, Ecology, and Conservation’ by L. David Mech states: “Wolves usually tear into the body cavity of large prey and … consume the larger internal organs, such as lungs, heart, and liver. The large rumen is usually punctured during removal and its contents spilled. The vegetation in the intestinal tract is of no interest to the wolves, but the stomach lining and intestinal wall are consumed, and their contents further strewn about the kill site.”(22)

 “To grow and maintain their own bodies, wolves need to ingest all the major parts of their herbivorous prey, except the plants in the digestive system.”(22)

 ​​Over a thirty year period Fleming et al. 2001 gathered an impressive amount of stomach samples of some 13,000 dingo hybrids (dog and dingo mixes) and feral domestic dogs spanning the six regions of the Australian continent. Although not ethically sound what they discovered is quite intriguing. Their results concluded that 97% of their diet was made up of animal protein. 72% of that was of mammals such as rabbits and kangaroos, 25% was that of insects, birds, fish, crabs, frogs and reptiles. The remaining 3% consisted of seeds and stomach contents of small birds which would have been too difficult to shake free. (23) 

Another large review performed by the British Journal of Nutrition studies some 31,276 wolf scat and stomach contents revealed there’s a “negligible amount of vegetable matter” being consumed. Much like the dingo hybrids and feral dogs above one or two studies concluded there was only around 2%-3% plant matter found. This brings to light that not all wolves gorge on things like berries as some think. Only a few packs have been observed gorging on berries in the summer months. (24)

 

When it comes to carbohydrates which includes fruit, veggies, and grains there is no nutritional requirement for them in the diet. Even the AAFCO and the NRC state this:

“Thus, there appears to be no requirement for carbohydrate in dogs provided enough protein is given to supply the precursors for gluconeogenesis.”-Nutrient Requirements for Dogs and Cats (4)

 

“Dogs have no requirement for plant carbohydrate” - Association of American Feed Control Officials (AAFCO 2016)(25)

 

Along with there being no nutritional requirement, most carbohydrates don’t have a complete amino acid profile, they lack some essential vitamins and minerals such as Vitamin D, Taurine, and Vitamin B12. They don’t produce the proper gastrin release in the stomach in order for proper digestion. They don’t have the right form of Omega 3 fatty acids. Plants contain the omega 3 fatty acid ALA. Dogs and cats require Omega 3s EPA and DHA. When an herbivore eats plants it can convert ALA to EPA and DHA. Your dog or cat cannot and therefore it must be provided in the diet by feeding oily fish, grass-fed and finished meat, whole prey, or by means of approved fish/krill oils.

 

Some veggies like spinach and kale contain Oxalate Acid which studies have shown can exacerbate stone and urolith formation(26). Sugary carbs like carrots, berries, etc can be the reason for yeast overgrowth.  They don’t contain the right form of Vitamin A but a precursor to it (beta-Carotene). Humans and carnivores need the retinol form of Vitamin A, not the carotenoid forms. Retinol Vitamin A is found in fish oil, eggs, meat, liver and animal fats. It cannot be found in plant products. The body needs to convert carotene to retinol, a form of vitamin A that it can use.


 

On top of that, carbohydrates have other antinutrients as well. Antinutrients are plant compounds that reduce the body's ability to absorb essential nutrients. This can lead to health issues in both humans and in companion animals. These anti-nutrients include Goitrogens which disrupt the production of thyroid hormones. Lectins which in large amounts can inhibit the body’s ability to absorb nutrients. Phytate (phytic acid), Tannins, Solanine the list goes on.

 

In conclusion your dog IS a carnivore….

“...carnivores such as dogs and cats….” Akers and Denbow 2008(5)

“...dogs are carnivores..” NRC 2006(4)

“...dogs have the internal anatomy and physiology of a carnivore…” Feldhamer 2003(2)

And thus they have no need for fruits and vegetables in their diet. As long as you are providing a variety of meat protein, animal fat, edible bones, organs, fish and eggs they will be getting everything they need. 

 Keeping in mind that when not feeding a fully wild prey diet some farm raised (non grass fed/finished) meats can be lacking in certain nutrients due to soil depletion. In this case adding in supplemental ingredients such as kelp(seaweed)& mussels can be beneficial for added nutrients. 

 

 

 

 

References:

  1. Stevens, C.E. and Hume, I.D. (1995). Comparative physiology of the vertebrate digestive system (2nd edition). New York: Cambridge University Press

  2. Feldhamer, G.A. (2003). Mammalogy: Adaptation, diversity, and ecology, 2nd Ed. New York: McGraw-Hill

  3. O’Reece, W. (2004). Dukes’ physiology of domestic animals (12th ed.) Ithaca, NY: Comstock Publishing

  4. National Research Council (NRC) (2006). Nutrient Requirements of dogs and cats. Washington, D.C.: National Academies Press  

  5. Akers, R.M. and Denbow, D.M. (2008). Anatomy and Physiology of domestic animals. Oxford: Blackwell

  6. Serpell, J. (1995). The domestic dog: Its evolution, behaviour, and interactions with people. Cambridge, UK: Cambridge University Press 

  7. Bradshaw, J.W.S. (2006). The Evolutionary Basis of Feeding Behavior of Domestic Dogs (Canis Familiaris) and Cats ( Felis catus). Journal of Nutrition 2006, 136(7): 1927S-1931S

  8. Coppinger, R. and Coppinger, L. (2001). Dogs: A new understanding of canine origin, behavior and evolution. Chicago, IL: University Chicago Press

  9. Pasquini, C., Spurgeon, T. and Pasquini, S. (1989). Anatomy of domestic animals: Systemic and regional approach (10th ed). Pilot Point, TX: Sudz Publishing 

  10. Boudreau, J.C. (1989). Neurophysiology and Stimulus chemistry of mammalian taste systems. In: Teranishi R, Buttery RG, Shahadi F, editors. Flavor chemistry trends and developments, p122-137. American Chemical Society Symposium Series no 67; Washington, D.C.: American Chemical Society

  11. Houpt, K.A., Hintz, H.F. and Shepherd, P. (1978). The role of olfaction in canine food preferences Chemical Senses, 3(3): 281-290

  12. Beaver, B.V., Fischer, M. and Atkinson, C.E. (1992). Determination of favorite components of garbage by dogs. Applied Animal Behavior Science, 34(1-2): 129-136

  13. Kitchell, R.L. (1972). Dogs know what they like. Friskies Research Digest 8: 1-42 

  14. Houpt, K.A. and Smith, S.L. (1981). Taste preferences and their relation to obesity in dogs and cats. Canadian Veterinary Journal, 22(4): 77-81

  15. Suchodolski, J.S. (2005). Assessment of the canine intestinal microflora using molecular methods and serum markers. PhD Thesis Texas A&M University

  16. Itoh, Z., Honda, R., Aizawa, I..(1980). Diurnal pH changes in duodenum of conscious dogs. American Journal of Physiology, 238(2): 91-96

  17. Youngberg, C.A., Wlodyga, J., Schmaltz, S., Dressman, J.B. (1985). Radiotelemetric determination of gastrointestinal pH in four healthy beagles. American Journal of Veterinary Research, 46(7): 1516-1521

  18. Sagawa, K., Li, F., Liese, R. and Sutton, S.C. (2009). Fed and fasted gastric pH and gastric residence time in conscious beagle dogs. Journal of Pharmacological Science, 98(7): 2494-2500

  19. Meyer, J.H., Thomson, J.B. And Cohen, B. (1979). Sieving a solid food by the normal and ulcer-operated canine stomach. Gastroenterology 76: 804-813

  20. Inchley, C.E., Larbey, C.D.A., Shwan, N.A. et al. (2016)Selective sweep on human amylase genes postdates the split with Neanderthals. Scientific Reports, (6): 37198

  21. Pajic, P., Pavlidis, P., Dean, K. et al. (2019). Independent amylase gene copy number bursts correlate with dietary preferences in mammals. eLife, 8: e44628

  22. Mech L.D. and Biotani L. (Eds) (2003). Wolves: Behavior, Ecology, and Conservation. University of Chicago Press

  23. Fleming, F., Corbett, L., Harden, R. and Thomson, P. (2001). Managing the impacts of dingoes and other wild dogs. Canberra, Australia: National Heritage Trust, Bureau of Rural Sciences 

  24. Bosch, G., Hagen-Plantinga, E.A. and Hendriks, W.H. (2015). Dietary nutrient profiles of wild wolves: insights for optimal dog nutrition? British Journal of Nutrition (2015), 113, S40-S54

  25. AAFCO (Association of American Feed Control Officials) 2016. Official Publication, See AAFCO.org

  26. Asia Pac Clin Nutr. 1999 Mar;8(1):64-74.

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