“But she’s a carnivore! Shouldn’t she just eat meat?!”

This catchcry has become so commonplace in veterinary clinics around the world thanks to the marketing jargon and buzzwords being spun as fact by pet food companies. Many pet owners have been manipulated to believe that the only way to feed pets is meat, meat and more meat with nothing else to provide a balanced diet.

So let’s unpack this – does being a carnivore mean that they can only eat meat? What about carbohydrates? What is a carnivore and how is it biologically different to an omnivore? What makes a carnivore special?

Firstly, what is a carnivore?
A carnivore is defined as an organism that eats mostly meat, or the flesh of animals. The word carnivore literally means meat-eater. Where it gets confusing, is that “carnivore” may also refer to animals categorised in the mammalian order of Carnivora, but this is somewhat misleading: many, but not all members of this order are meat eaters, and even fewer are true obligate carnivores. For example, while the Arctic polar bear eats meat almost exclusively with a diet of more than 90% meat, most species of bears are omnivorous. Carnivores may also be classified according to the percentage of meat comprising their diet; a hypercarnivore’s diet consists of more than 70% meat, compared to that of a mesocarnivore (30–70%) and a hypocarnivore (less than 30%). When talking about companion animals, domestic cats are obligate carnivores – also know as hypercarnivores – and dogs are omnivores due to their ability to synthesise nutrients they require without the need for meat in the diet.

What does obligate carnivore mean?
An obligate carnivore is an organism whose diet requires nutrients found only in animal flesh. This does not mean they require a diet of only meat – it means their diet must have meat in it to meet their requirements. Specifically, cats are unable to synthesize essential nutrients such as retinol, arginine, taurine, and arachidonic acid so in nature they must consume meat to supply these nutrients. Obligate carnivores can ingest plant material and digest it to varying degrees, but may also ingest it purposely to induce vomiting.

What is special about carnivore digestion?
While there’s a huge variety of animals that are considered carnivores and their physiology varies widely, but there are a few features of their digestion that set them apart from omnivores. As we discussed before, a carnivore needs a portion of their diet to contain meat to meet their nutritional requirements. This is because their body cannot make vital nutrients from cofactors or precursors – dogs for example, can make taurine from cysteine and methionine so do not require meat in their diet to meet this requirement. Cats however, must have taurine present in the diet, which is only available from an animal protein source. The other thing that is special about carnivores and their digestive system is it is generally very short from start to finish; their stomach is small, and their intestinal tract is very short. This is because they do not need to do as much extensive digesting and absorbing of nutrients in their intestines compared to a herbivore or a omnivore as meat is much easier to digest than plant material – most of the digestion occurs in the stomach and is mostly broken down when it reaches the intestines. They generally do not chew their food but will swallow pieces whole where they are digested in the stomach, this is because their saliva does not contain digestive enzymes unlike a herbivore and some omnivores.

What should a carnivore be eating? Can carnivores eat carbohydrates?
Depending on the type of carnivore (hypo-, meso- or hyper-carnivore), the diet will vary significantly. An obligate carnivore is a hyper-carnivore, which means they require at least 70% of the diet to be meat. This means the remainder of the diet will be comprised of plants, fungi and other nutrients. Being a hyper-carnivore does not mean that they cannot eat any form of plant matter, it simply means they require a larger portion of meat in the diet than plant material as they get majority of their nutrients from meat. So, this is why it’s completely fine for a carnivore to ingest carbohydrates and eat plant matter, it just should not be their sole diet.

Still have questions about carnivores? Leave them in the comments below!

References

https://www.evolvingsciences.com/Carnivore%20digestive%20system.html

https://www.nationalgeographic.org/encyclopedia/carnivore/#:~:text=Some%20carnivores%2C%20called%20obligate%20carnivores,enough%20nutrients%20for%20obligate%20carnivores.&text=All%20obligate%20carnivores%2C%20including%20cats%2C%20are%20hypercarnivores.

https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.7885

https://www.cambridge.org/core/journals/proceedings-of-the-nutrition-society/article/differences-between-cats-and-dogs-a-nutritional-view/A01A77BABD1B6DDD500145D7A02D67A5

Ullrey, D. E. (2004). “Nutrient Requirements: Carnivores”. In Pond, Wilson (ed.). Encyclopedia of Animal Science. CRC Press. p. 670. ISBN 978-0-8247-5496-9.

Glen, Alistair & Dickman, Christopher (Eds) 2014, Carnivores of Australia, CSIRO Publishing, Melbourne, ISBN 978-0-643-10310-8.