Vegetarian Diets for Dogs & Cats

Pet owners frequently project their beliefs about human health onto their companion animals. Anxieties about purported harms from vaccines in children, for example, have spurred an anti-vaccination movement among vets and pet owners.1–4Beliefs in alternative medical therapies for people, such as herbal medicine and acupuncture, may motivate pet owners to seek such treatments for their animals. But perhaps the most common example of this phenomenon is the translation of dietary beliefs and fads from human nutrition to animal feeding practices.5

This projection of human dietary practices onto pets takes many forms. On the heels of a wave of hysteria about gluten and the health effects of grains in humans, we saw the rise in popularity of grain-free pet foods, which now make up close to half of commercial diets for dogs and cats.6Organic ingredients are often marketed to pet owners as having health benefits based on the belief that this is true for people, despite the lack of real evidence for this in humans or in other animals.7And among those who minimize or avoid animal products in their own diet, there is significant interest in feeding such vegetarian or vegan diets to their pets.8

People may avoid meat or other animal products in their diet for a variety of reasons, including concerns about food animal welfare, beliefs about the health effects of plant-based and animal-based foods, and religious dietary restrictions. Surveys of pet owners indicate that those who follow a vegan diet (eating no animal-based foods) or other vegetarian diets (limited consumption of some types of animal-based foods) sometimes feel discomfort at violating their own dietary rules in the feeding of their dogs and cats, especially if their own food choices are driven by religious or ethical concerns.8–11They have a clear interest and motivation to feed vegetarian or vegan diets to their pets, but many do not because of concerns about the health effects of such diets on their pets.8

Beliefs about the nutritional requirements of dogs and cats are often based on the notion that whatever wild canids and felids eat must be a “natural,” and thus a healthy diet for our pets. However, wild carnivores often suffer from malnutrition, parasitism, and other ills associated with their diet, so it is a mistake to imagine that the diet available to them in the wild is perfectly suited to optimize their health.12–23Natural history does have an influence the nutritional requirements of a species, but these requirements are not always best met by feeding a diet identical to that eaten by the wild ancestors of modern animals. This is especially true for animals that have been domesticated, a process which induces significant changes to the anatomy and physiology of domestic species.

Dogs have been dramatically impacted by their long association with humans. Some of these changes are obvious, and their relevance to the concept of a “natural” diet like that of wolves and wild dogs is clear. It is unlikely that a pack of feral pugs or French bulldogs will even be seen running down and savaging an elk or antelope, and the idea that this would be an optimal diet for them is clearly ridiculous. However, even breeds with a more typically canine anatomy have undergone changes in morphology and physiology that reflect their adaptation to human foods. From their dentition to their ability to digest starches and taste sweetness, dogs have been shaped by domestication, and they are well-suited to an omnivorous diet.24–27

In theory, then, dogs should be able to thrive on vegetarian or vegan diets. However, there have been few studies demonstrating this, and such diets can still be problematic. A vegan diet must be properly and carefully formulated to meet the nutritional needs of dogs, and there is less room for error than with diets containing animal ingredients. Numerous studies of commercial vegan and vegetarian pet foods have found formulation errors and inadequacies in essential nutrients.9,28Some studies have also found mammalian DNA in such diets, suggesting they may not even be accurately labeled as vegetarian or vegan.29

Even diets which appear adequate on paper or in laboratory testing, however, may not support normal health under real-world conditions. Most commercial grain-free diets, for example, should be nutritionally complete for dogs, yet recent reports of cardiomyopathy in dogs eating such diets suggest a serious health risk for some individuals fed these diets.30–32At present, there are only short-term studies and uncontrolled, low-quality case series evaluating the health of dogs fed vegan or vegetarian diets.9,33Such limited evidence leaves significant uncertainty about the risks and benefits of such diets for domestic dogs.

Cats have been more lightly touched by domestication and artificial selection than dogs, and they are clearly still obligate carnivores.34,35This does not mean they are healthiest when fed only raw birds and small mammals, and in fact the evidence indicates this is not the safest or healthiest diet for domestic cats.36,37However, domestication has had limited effects on the physiology of cats, and their dietary requirements are unlikely to be effectively met by plant-only diets. The need for preformed vitamin A, taurine and other specific amino acids lacking in plant-based foods, and other specific and known dietary requirements of cats makes it unlikely that long-term feeding of vegan diets will support good health in this species.35,38

There are few studies evaluating the health effects of plant-based diets on cats. Some research on cats fed commercial vegetarian diets by their owners have found deficiencies in some nutrients in some cats, but the evidence is limited and of low quality, so no robust conclusions can be drawn.9,39–41

Bottom Line

There is no evidence that vegetarian diets have health benefits for dogs and cats, and no real reason to believe they should based on the physiology and nutritional requirements of these species. Pet owners may choose to feed such diets due to their philosophical or religious beliefs, but veterinarians should make it clear that any potential health benefits of vegetarianism for humans likely do not apply to our dogs and cats.

Dogs are omnivores shaped by domestication to be able to eat both plant and animal foods, and in theory they should be able to thrive on vegetarian or vegan diets. However, these diets must be carefully formulated, and many commercial vegetarian dog foods do not appear to be nutritionally adequate. There is also little reliable research evidence showing that dogs can remain healthy fed only a vegan diet. Given the unexpected health problems seen with theoretically adequate grain-free diets, we should be cautious about the potential risks of vegetarian diets for dogs until there is better evidence showing their long-term health effects.

Cats are clearly obligate carnivores with nutritional requirements that are unlikely to be effectively met by vegan diets. Such diets offer only risks and no benefits for cats and should be avoided.

References

1.        Clifton J. Stop the Shots!?: Are Vaccinations Killing Our Pets?New York, NY: Foley Square Books; 2007.

2.        Duan N. Inside the World of Pet Anti-Vaxxers. The Awl.com. January 2018.

3.        Kluger J. Some Anti-Vaxxers Aren’t Getting Their Pets Vaccinated. Here’s Why That’s So Dangerous. Time.com. March 2019.

4.        Ducharme J. Veterinary Group: Dogs Can’t Get Autism, So Please Keep Vaccinating Them. Time.com. 2018.

5.        Walet E. Are trends in Human Food reflected in Pet Food Purchase? 2015. https://dspace.ou.nl/bitstream/1820/6538/1/Walet E scriptie.pdf. Accessed December 20, 2018.

6.        Phillips-Donaldson D. Are grain-free pet foods truly healthy and sustainable? Pet Food Ind. 2017.

7.        Smith-Spangler C, Brandeau ML, Hunter GE, et al. Are Organic Foods Safer or Healthier Than Conventional Alternatives? Ann Intern Med. 2012;157(5):348. doi:10.7326/0003-4819-157-5-201209040-00007

8.        Dodd SAS, Cave NJ, Adolphe JL, Shoveller AK, Verbrugghe A. Plant-based (vegan) diets for pets: A survey of pet owner attitudes and feeding practices. Suchodolski JS, ed. PLoS One. 2019;14(1):e0210806. doi:10.1371/journal.pone.0210806

9.        Knight A, Leitsberger M, Knight A, Leitsberger M. Vegetarian versus Meat-Based Diets for Companion Animals. Animals. 2016;6(9):57. doi:10.3390/ani6090057

10.      Rothgerber H. A meaty matter. Pet diet and the vegetarian’s dilemma. Appetite. 2013;68:76-82. doi:10.1016/j.appet.2013.04.012

11.      Wakefield LA, Shofer FS, Michel KE. Evaluation of cats fed vegetarian diets and attitudes of their caregivers. J Am Vet Med Assoc. 2006;229(1):70-73. doi:10.2460/javma.229.1.70

12.      Tidière M, Gaillard J-M, Berger V, et al. Comparative analyses of longevity and senescence reveal variable survival benefits of living in zoos across mammals. Sci Rep. 2016;6:36361. doi:10.1038/srep36361

13.      Mukherjee S, Heithaus MR. Dangerous prey and daring predators: a review. Biol Rev. 2013;88(3):550-563. doi:10.1111/brv.12014

14.      Woodroffe R, Davies-Mostert H, Ginsberg J, et al. Rates and causes of mortality in Endangered African wild dogs Lycaon pictus: lessons for management and monitoring. Oryx. 2007;41(02):215. doi:10.1017/S0030605307001809

15.      Mech LD. Productivity, Mortality, and Population Trends of Wolves in Northeastern Minnesota. J Mammal. 1977;58(4):559-574. doi:10.2307/1380004

16.      Young TP. Natural Die-Offs of Large Mammals: Implications for Conservation. Conserv Biol. 1994;8(2):410-418. doi:10.1046/j.1523-1739.1994.08020410.x

17.      Holmes JC, Podesta R. The helminths of wolves and coyotes from the forested regions of Alberta. Can J Zool. 1968;46(6):1193-1204. doi:10.1139/z68-169

18.      Bosch G, Hagen-Plantinga EA, Hendriks WH. Dietary nutrient profiles of wild wolves: insights for optimal dog nutrition? Br J Nutr. 2015;113(S1):S40-S54. doi:10.1017/S0007114514002311

19.      Choquette LPE, Gibson GG, Kuyt E, Pearson AM. Helminths of wolves, Canis lupusL., in the Yukon and Northwest Territories. Can J Zool. 1973;51(10):1087-1091. doi:10.1139/z73-158

20.      Amanda A. Parasites of the African painted dog (Lycaon pictus) in captive and wild populations: Implications for conservation. 2011. http://researchrepository.murdoch.edu.au/id/eprint/10519/2/02Whole.pdf.

21.      Berentsen AR, Becker MS, Stockdale-Walden H, Matandiko W, McRobb R, Dunbar MR. Survey of gastrointestinal parasite infection in African lion ( Panthera leo), African wild dog ( Lycaon pictus) and spotted hyaena ( Crocuta crocuta) in the Luangwa Valley, Zambia. African Zool. 2012;47(2):363-368. doi:10.1080/15627020.2012.11407561

22.      Fuchs B. Sarcoptic mange in the Scandinavian wolf population. 2014. https://brage.bibsys.no/xmlui/bitstream/handle/11250/222199/Boris Fuchs.pdf?sequence=1. Accessed December 28, 2018.

23.      Benson JF, Mills KJ, Loveless KM, Patterson BR. Genetic and environmental influences on pup mortality risk for wolves and coyotes within a Canis hybrid zone. Biol Conserv. 2013;166:133-141. doi:10.1016/J.BIOCON.2013.06.018

24.      Vilà C, Maldonado JE, Wayne RK. Phylogenetic relationships, evolution, and genetic diversity of the domestic dog. J Hered. 90(1):71-77. http://www.ncbi.nlm.nih.gov/pubmed/9987908. Accessed October 27, 2018.

25.      Serpell J, Barrett P. The Domestic Dog?: Its Evolution, Behavior and Interactions with People. Second edition.; 2017. https://www.worldcat.org/title/domestic-dog-its-evolution-behavior-and-interactions-with-people/oclc/987274028&referer=brief_results. Accessed October 27, 2018.

26.      Axelsson E, Ratnakumar A, Arendt M-L, et al. The genomic signature of dog domestication reveals adaptation to a starch-rich diet. Nature. 2013;495(7441):360-364. doi:10.1038/nature11837

27.      Reiter T, Jagoda E, Capellini TD. Dietary Variation and Evolution of Gene Copy Number among Dog Breeds. 2016. doi:10.1371/journal.pone.0148899

28.      Kanakubo K, Fascetti AJ, Larsen JA. Assessment of protein and amino acid concentrations and labeling adequacy of commercial vegetarian diets formulated for dogs and cats. J Am Vet Med Assoc. 2015;247(4):385-392. doi:10.2460/javma.247.4.385

29.      Kanakubo K, Fascetti AJ, Larsen JA. Determination of mammalian deoxyribonucleic acid (DNA) in commercial vegetarian and vegan diets for dogs and cats. J Anim Physiol Anim Nutr (Berl). 2017;101(1):70-74. doi:10.1111/jpn.12506

30.      Adin D, DeFrancesco TC, Keene B, et al. Echocardiographic phenotype of canine dilated cardiomyopathy differs based on diet type. J Vet Cardiol. 2019;21:1-9. doi:10.1016/J.JVC.2018.11.002

31.      Kaplan JL, Stern JA, Fascetti AJ, et al. Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets. Loor JJ, ed. PLoS One. 2018;13(12):e0209112. doi:10.1371/journal.pone.0209112

32.      Freeman LM, Stern JA, Fries R, Adin DB, Rush JE. Diet-associated dilated cardiomyopathy in dogs: what do we know? J Am Vet Med Assoc. 2018;253(11):1390-1394. doi:10.2460/javma.253.11.1390

33.      Brown WY, Vanselow BA, Redman AJ, Pluske JR. An experimental meat-free diet maintained haematological characteristics in sprint-racing sled dogs. Br J Nutr. 2009;102(09):1318. doi:10.1017/S0007114509389254

34.      MacDonald ML, Rogers QR, Morris JG. Nutrition of the Domestic Cat, a Mammalian Carnivore. Annu Rev Nutr. 1984;4(1):521-562. doi:10.1146/annurev.nu.04.070184.002513

35.      Morris JG. Idiosyncratic nutrient requirements of cats appear to be diet-induced evolutionary adaptations. Nutr Res Rev. 2002;15(01):153. doi:10.1079/NRR200238

36.      Glasgow A, Caver N, Marks S, Pedersen N. Role of Diet in the Health of the Feline Intestinal Tract and in Inflammatory Bowel Disease.; 2002. http://www.vetmed.ucdavis.edu/ccah/530-752-7295. Accessed December 28, 2018.

37.      Schlesinger DP, Joffe DJ. Raw food diets in companion animals: a critical review. Can Vet J = La Rev Vet Can. 2011;52(1):50-54. http://www.ncbi.nlm.nih.gov/pubmed/21461207. Accessed October 27, 2018.

38.      Weeth L, Chandler M. Vegetarian Diets. Clin Br. 2015;(January):61-63. https://www.cliniciansbrief.com/article/vegetarian-diets. Accessed April 29, 2019.

39.      Leon A, Bain SA, Levick WR. Hypokalaemic episodic polymyopathy in cats fed a vegetarian diet. Aust Vet J. 1992;69(10):249-254. http://www.ncbi.nlm.nih.gov/pubmed/1359869. Accessed April 29, 2019.

40.      Wakefield L, Michel KE. Taurine And Cobalamin Status of Cats Fed Vegetarian Diets. J Anim Physiol Anim Nutr (Berl). 2005;89(11-12):427-428. doi:10.1111/j.1439-0396.2005.00611_2.x

41.      Gray CM, Sellon RK, Freeman LM. Nutritional adequacy of two vegan diets for cats. J Am Vet Med Assoc. 2004;225(11):1670-1675. http://www.ncbi.nlm.nih.gov/pubmed/15626215. Accessed April 29, 2019.

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2 Responses to Vegetarian Diets for Dogs & Cats

  1. Jen Robinson says:

    As I read it, this and your previous post both suggest a scarcity of long-term feeding trial data.
    Am I correct in the understanding that the basis for labeling a food as ‘nutritionally complete’ is a few months of trials, often with a single breed, with intensive monitoring of blood and urine chemistry and other measurable indices? Is that really adequate?

  2. skeptvet says:

    You are correct that “complete and balanced” is a designation that can be met without feeding trials (by showing adherence to established nutrient requirements for dogs or cats and recommended formulation methods) or with short-term feeding trials (usually < 6 months). Whether this is "adequate" is open for debate. We would certainly have better information if every food marketed were fed to various breeds of dogs for their lifetime, or at least for a reasonable proportion of their lifetime, but that is not a realistic standard since it would require the use of a lot of dogs as lifelong lab subjects (ethically questionable), would be extremely slow and expensive (making many foods unavailable or unaffordable) and would need to be repeated for any change in formulation (which is common as the availability of commodities and nutrient sources changes). The real question is what could we realistically and ethically do that would be better than the current system? I would think a structured and robust post-marketing surveillance system capturing data in owned pets would be more useful and practical than long-term pre-marketing feeding trials.

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