Why Are Cats Obligate Carnivores And What Does It Mean?

Why Are Cats Obligate Carnivores And What Does It Mean?

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At a glance

Why are cats obligate carnivores?

Cats are unable to synthesise specific vitamins, amino acids and fatty acids and must obtain them in their pre-formed state from the meat and organs they consume, which makes the carnivore diet a biological necessity. 

The cat’s body has evolved to catch, eat and digest meat with retractable claws, eyes in the front of the skull, shearing teeth and a short digestive tract.

 

Carnivora (which means flesh devourers in Latin) is an order of mammals which eat meat. Cats are obligate carnivores (also known as hypercarnivores or true carnivores) who have evolved unique anatomic, physiologic, metabolic and behavioural adaptations consistent with eating a strictly carnivorous diet. An obligate carnivore is an animal who must consume meat out of biological necessity because they are unable to manufacture (synthesise) essential nutrients and must get from food.  It is not necessary for the cat to make these nutrients, as the animals they are eating have already done it for them and contain all the essential nutrients in their pre-formed state.

Cats lack the physiology required for the efficient digestion of vegetable matter and many cats eat plants (especially grass) specifically to vomit.

Essential ingredients in the cat’s diet

Amino acids

Amino acids are the building blocks of proteins; every cell in the body is made up of protein. The cat can create several amino acids from other amino acids; however, the cat cannot synthesise several amino acids, which makes them essential as the cat.

Amino acids are necessary  for healthy physiological function, which includes the growth of kittens, and processes such as elimination of nitrogenous waste and hemoglobin synthesis.

Cats use 20 amino acids, 11 of which are essential.

Essential amino acids:

  • Arginine
  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Taurine
  • Threonine
  • Tryptophan
  • Valine

Vitamins

The word vitamin comes from the words vita, which means life and the chemical word amine, vital for life. Vitamins are necessary for vision and skin health, metabolism, blood clotting, antioxidants, nervous system, growth, hair, cell energy and the formation of blood cells.

There are two groups of vitamins, fat-soluble (vitamin A, D, E and K), and water-soluble (B1, 2, 3, 5, 6, 7, 9, 12 and C). Excessive consumption of fat-soluble vitamins can cause toxicity; however, excess water-soluble vitamins pass out of the body via the urine.

Essential vitamins:

  • Vitamin A
  • Vitamin B12
  • Vitamin D
  • Vitamin E

Omega 3 and 6 fatty acids

Omega fatty acids are made up of long chains of carbon and hydrogen atoms and are important dietary fats necessary for several biological processes in the body. They are responsible for the maintenance of healthy skin and coat, energy, fight inflammation, reproductive development, brain development and function and a strong immune system.

The most common type of fatty acids include:

Omega-3 fatty acids:

  • Alpha-linolenic acid (ALA)
  • Eicosapentaenoic acid (EPA)
  • Docosahexaenoic acid (DHA)

Omega-6 fatty acids:

  • Linoleic acid (LA)
  • Gamma-linolenic acid (GLA)
  • Dihomo-gamma-linolenic acid (DGLA)
  • Arachidonic acid (AA)

Essential fatty acids:

  • Linoleic acid (LA)
  • Alpha-linolenic acid
  • Eicosapentaenoic acid (EPA)
  • Docosahexaenoic acid (DHA)

Biological features of the obligate carnivore

Like their wild counterparts, cats are built for hunting and have several features which separate them from herbivores.

Digestive tract:

Cat digestive tract
Feline digestive tract

The cat’s digestive tract is designed to digest protein and fat; it is short in relation to body length, to digest food quickly. Herbivores need a longer gut and fermenting bacteria to break down the cell walls of plant material.

The short length of the digestive tract weighs less than other animals, which allows the cat to be active predators.

Teeth:

Cat teeth
The cat’s teeth are designed for inflicting a fatal bite and cutting through meat.

The carnassial teeth (are paired upper and lower teeth) are designed to deliver the cervical bite to sever the spinal cord and kill prey and enable the cat to slice meat from their prey.

The four long canine teeth allow the cat grip and tear food.

The jaws of the cat only move vertically, as they do not need to grind their food, which is essential for digesting the carbohydrates in plants.

Ears:

Maine Coon ears

Cats have a well-developed sense of hearing, with ears which face forward and 20 associated muscles which help the cat to precisely locate a sound.

Tongue:

Papillae on a cat's tongue
Close up of the papillae on a cat’s tongue.

The tongue contains backward-facing hooks (papillae) which are useful for rasping meat off bones and grooming.

Saliva:

Cats are unable to produce the digestive enzyme amylase, which is found in the saliva of herbivores to initiate the digestion of dietary starches while chewing.

Eyes:

tapetum lucidum
Tapetum lucidum

The eyes of the cat are located in the front of the skull, which increases depth perception for hunting. Their ability to see in low light (scotopic vision) is due to the high number of rod cells in the retina, in fact, cats have 6-8 times more rod cells in the retina than humans.

The characteristic flow we see in the eyes of cats in the dark comes from the tapetum lucidum, a layer of tissue which lies immediately behind the retina at the back of the eye. It reflects visible light back through the retina which increases the light available to the photoreceptors (rods) which also enhances the cat’s vision in low light.

Jaw:

The cat's jaw cannot move sideways

Like other mammals that eat meat, a cat’s jaws only move up and down, not side to side. The jaw is strong and opens wide, to capture prey and tear flesh.

Retractible claws:

Cat claws

Sharp, curved claws which are designed for climbing, capture and secure pray but retract when the cat walks which decreases noise when stalking and prevents wear and tear of the claws.

Gluconeogenesis:

Cats can meet their blood glucose requirements from gluconeogenesis, the production glucose in the body from non-sugar sources, mainly proteins instead of carbohydrates. In the absence of protein to meet their energy needs, the body will break down its own muscle and organs.

Unable to taste sweet:

The ability to perceive sweet-tasting compounds is encoded by the TAS1R gene; cats have a mutation on this gene mutation, which rendered their taste receptors unable to bind to sweet molecules. Because cats are carnivorous, this gene mutation had no impact.

Frequently asked questions

Are dogs obligate carnivores too?

Dogs are facultative carnivores, which means they do best on a carnivore duet but can eat non-animal food.

What are humans?

Humans are omnivores who can eat a wide variety of foods which include meat and plants.

Are cats the only obligate carnivores?

No, several other animals are also obligate carnivores, which include mink, dolphins, seals, sea lions, salmon, hawks, eagles and walruses.