Updated: Dec 16, 2021
Whether cat or dog domesticated or wild, these creates are carnivores (1). Despite what the pet food industry and conglomerate companies tell you, there is no escaping the fact, cats and dogs are carnivores through and through. Some claim our companions have adapted to a dry cereal-based diet but while the first dog food biscuit made its debut in 1860’s, it wasn’t widely available and fed in pet owning homes until 1941, 77 years ago around World War II when materials and meat products were being rationed and were sparse (2). We humans may have bred these creatures so much resulting in now hundreds of different breeds, but this is not enough time for a species to completely evolve an entirely different physiological and anatomical system (3). This is not only evident in the ailments that are all too common in our companions like digestive issues, kidney failure and dental diseases, but in their present-day anatomy.
Starting at the mouth, if you look at the teeth of a carnivore they are sharp, pointy and jagged meant for holding, tearing, shearing, and crushing. The jaw moves vertically, and the mouth also opens wide so that large pieces of meat can be consumed. All indicative of a meat-based diet. Herbivores on the other hand typically have teeth that are flat with a jaw that breaks down plant material by moving side to side (4,5).
Enzymatically cats and dogs do not have the enzyme, amylase (6) responsible for breaking down carbohydrates which include grains, fruits and vegetables or cellulase for breaking down cellulose which is about 33% of a plant’s make up and the main component of the plant cell wall (7). Canines and felines do however have the enzyme, trypsin, which is made in the small intestine after an enzyme from the pancreas activates trypsinogen, specifically for breaking down meats. (8,9) The pancreas can make amylase but in order for this organ to do so, a lot of stain must be put on it for this to happen (10, 11, 12, 13).
Systematically, the stomach is the first stop after the mouth, to digest protein. It has the capability to produce extremely strong hydrochloric acid at around 1-2 pH which can not only break down protein but, annihilate bacteria in meat. Herbivores and omnivores like humans in comparison have a stomach pH closer to 4-5 pH (14).
Next food stuff travels through the intestines. Unlike humans, felines and canines have a very short digestive tract (15) so food passes very fast and must be readily absorbable to be useful. Fat and protein are easily digested (16, 17, 18) but plant material takes much longer (15) to be digested and broken down, so more times than not it is passed through the system almost untouched. While human’s intestines are about 30 feet long, canine and felines are only about 3 times it’s body length. (15) A short digestive tract is important to note as it can process rancid or even bacteria ridden meat quickly without being to affected by it (14).
Finally, it comes out of the body as fecal matter. When our companions are on dry kibble diets we notice the smell of all the fillers that were not properly digested present in stinky waste. When our companions are on a diet consisting of meat, their waste have little to no smell, the size is three quarters that of a kibble fed companion (19) and they frequent the yard or litter box with feces half as much.
As one can see nothing about a canine or feline is meant to consume a plant based or dry cereal-based diet no matter what we see advertised or heard about from professionals. From the teeth down to the fecal matter it is evident that these creatures should consume and thrive on meat. Through and through they are CARNIVORES.
Ann Wortinger, BIS, LVT, VTS, "Cats: Obligate Carnivore," CVC in Kansas City Proceedings, Aug 1, 2010.
Canine Nutrition: Choosing the Best Food for Your Breed
Wang, Xiaoming; Tedford, Richard H.; Dogs: Their Fossil Relatives and Evolutionary History. New York: Columbia University Press, 2008. ISBN 0231135289, p
d e Muizon, Christian; Lange-Badré, Brigitte (1997). "Carnivorous dental adaptations in tribosphenic mammals and phylogenetic reconstruction". Lethaia. 30(4): 353–366. doi:10.1111/j.1502-3931.1997.tb00481.x
Kienzle E. 1993. “Carbohydrate metabolism of the cat. 1. Activity of amylase in the gastrointestinal tract of the cat.” J. Anim. Physiol. Anim. Nutr. (Berl.) 69:92–101.
Brett, C.T. Physiology and Biochemistry of Plant Cell Walls. London: Unwin Hyman, 1990.
The German physiologist Wilhelm Kühne (1837-1900) discovered trypsin in 1876. See: W. Kühne (1877) "Über das Trypsin (Enzym des Pankreas)", Verhandlungen des naturhistorisch-medicinischen Vereins zu Heidelberg, new series, vol. 1, no. 3, pages 194-198.
Engelking, Larry R. (2015-01-01). Textbook of Veterinary Physiological Chemistry (Third Edition). Boston: Academic Press. pp. 39–44. ISBN 9780123919090.
Hore P, Messer M. Studies on disaccharidase activities of the small intestine of the domestic cat and other carnivorous mammals. Comp Biochem Physiol (1968) 24(3):717–2510.1016/0010-406X(68)90785-8
Batchelor DJ, Al-Rammahi M, Moran AW, Brand JG, Li X, Haskins M, et al. Sodium/glucose cotransporter-1, sweet receptor, and disaccharidase expression in the intestine of the domestic dog and cat: two species of different dietary habit. Am J Physiol Regul Integr Comp Physiol (2011) 300(1):R67–7510.1152/ajpregu.00262.2010
Hietanen E. Interspecific variation in the levels of intestinal alkaline phosphatase, adenosine triphosphatase and disaccharidases. Comp Biochem Physiol A Comp Physiol (1973) 46(2):359–6910.1016/0300-9629(73)90426-X
Verbrugghe, Adronie, and Myriam Hesta. “Cats and Carbohydrates: The Carnivore Fantasy?” Ed. Jacquie Rand. Veterinary Sciences 4.4 (2017): 55. PMC. Web. 14 July 2018.
Beasley, DeAnna E. et al. “The Evolution of Stomach Acidity and Its Relevance to the Human Microbiome.” Ed. Xiangzhen Li. PLoS ONE 10.7 (2015): e0134116. PMC. Web. 14 July 2018.
The Editors of Encyclopædia Britannica. “Digestion.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 8 Apr. 2016, www.britannica.com/science/digestion-biology.
Hamper, B A, et al. “Apparent Nutrient Digestibility of Two Raw Diets in Domestic Kittens.” Journal of Feline Medicine and Surgery., U.S. National Library of Medicine, Dec. 2016, www.ncbi.nlm.nih.gov/pubmed/26400072
Sá, Fabiano C. et al. “Comparison of the Digestive Efficiency of Extruded Diets Fed to Ferrets (Mustela Putorius Furo), Dogs (Canis Familiaris) and Cats (Felis Catus).” Journal of Nutritional Science 3 (2014): e32. PMC. Web. 16 Mar. 2018.
Bermingham, Emma N. et al. “Key Bacterial Families (Clostridiaceae, Erysipelotrichaceae and Bacteroidaceae) Are Related to the Digestion of Protein and Energy in Dogs.” Ed. Katrine
Kerr, K. R., Vester Boler, B. M., Morris, C. L., Liu, K. J., & Swanson, K. S. (2012). Apparent total tract energy and macronutrient digestibility and fecal fermentative end-product concentrations of domestic cats fed extruded, raw beef-based, and cooked beef-based diets. DOI: 10.2527/jas.2010-3266