Is the cat just a small dog?
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Time to read 14 min
Once you have tried sharing a garden, a house, a sofa – and yes, probably also a bed – with a cat, you know that a cat is NOT a small dog. Cats are entirely their own, and we humans have probably known that since we began letting cats into our lives several thousand years ago. When we look at the history of cat food, it took a little longer before we realized that cats are not small dogs. From the very beginning of the dog’s domestication, humans shared their food (read: scraps) with their newly acquired four-legged friend, whereas cats and humans benefited from each other in a slightly different way. Humans attracted plenty of mice by storing grain and other non-perishable foods close to or inside their homes, so the cat was practically served its food on a silver platter. A “win-win situation” for both parties, which humans and, among others, the classic farm cat still benefit from to this day.
Later in history – most likely in the Middle Ages – cats began expanding their culinary repertoire with leftovers from human kitchens. However, the primary source of nutrition remained small rodents and other animals that occasionally have a tendency to end up in a cat’s claws.
Copyright Sondre Eriksen Hensema / @we.are.chilipepper
At the end of the 19th century, the pet food industry was born – or more precisely, the dog food industry. The cats simply ate along when the dogs were served their canned food. From the beginning of the 20th century, humans learned the hard way that the cat is not just a small dog. Dog food worked anything but well for cats, which, among other things, began to develop reproductive disorders, neurological problems, and growth disturbances – at least if they were not allowed to meet the majority of their nutritional needs through hunting. The dogs showed none of these symptoms, even though they ate the same food. This prompted a closer investigation of the cat’s nutritional requirements, and fortunately we have become wiser today, even though we once again made mistakes when developing suitable commercially manufactured food for the couch tiger at home – but more on that later in the text.
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Copyright @levy_the_dog
Table of Content
A True Carnivore
Unlike the dog, the cat is a true carnivore. This became evident when we humans tried feeding our cats dog food. While dogs are able to synthesize some of the essential nutrients from precursors of these substances found in plant material, cats require the final forms of these nutrients, which occur exclusively or in significant amounts in animal-based ingredients.
One example is beta-carotene, which is found in carrots, sweet potatoes, spinach, and kale, among others. Dogs can convert beta-carotene into vitamin A, which is essential for both dogs and cats. In this way, the dog can partially meet its vitamin A requirements through the aforementioned vegetables. The cat cannot do this. The cat must obtain vitamin A through its food, which means it needs to eat liver, fish, and/or eggs in order to meet its vitamin A requirements and survive.
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Vitamin A is not the only essential nutrient that the cat – unlike the dog – cannot synthesize on its own and therefore must obtain through animal-based ingredients in its food.
Arachidonic Acid
The omega-6 fatty acid arachidonic acid occurs exclusively in animal fat. Both dogs and cats require this fatty acid for their metabolism, but dogs are able to synthesize arachidonic acid from the omega-6 fatty acid linoleic acid, which is also found in vegetable oils. Cats cannot do this, which makes arachidonic acid an essential fatty acid for cats. A deficiency in arachidonic acid can lead to a wide range of serious consequences for the cat, including reproductive disorders, skin and coat symptoms, growth and developmental disorders, and a weakened immune system.
Niacin (vitamin B3)
Although niacin is also found in plant-based ingredients, including grains and legumes, its biological availability—that is, the amount the body can actually utilize—is significantly lower than niacin from animal-based ingredients. Fortunately, dogs are able to synthesize niacin from the amino acid tryptophan and therefore do not require animal-based niacin. Cats, on the other hand, cannot synthesize niacin in sufficient amounts and must therefore eat food that is rich in meat and/or fish. Otherwise, a deficiency within just one to two weeks can lead to, among other things, changes in the mouth and mucous membranes, gastrointestinal symptoms, and neurological symptoms.
Copyright Sondre Eriksen Hensema / @we.are.chilipepper
Copyright Marie-Elisabeth Jørgensen / @willemsfotografi
Copyright Natacha Van Bossche / @cooptheadventurousgsp
Taurine
The most prominent nutrient when we talk about cat food is probably taurine. Taurine is an amino acid that plays an important role in, among other things, fat digestion, heart health, normal vision, and reproduction. That cats – unlike the vast majority of dogs – must be supplied with a fairly significant amount of taurine through their food is a relatively recent discovery. It was not until the late 1960s that it was discovered that the lack of taurine in commercially manufactured food was likely one of the reasons for the increasing number of sick cats. And since the 1980s, after more and more cats died from the heart disease dilated cardiomyopathy and taurine deficiency was identified as the cause, taurine has been considered an essential amino acid for cats. Taurine occurs exclusively in animal-based ingredients, with heart being the absolute winner in terms of taurine concentration. Heart is therefore an extremely healthy and tasty snack for a cat. Highly heat-processed and long-shelf-life food is, moreover, particularly critical for cats, as taurine is sensitive to both heat treatment and long storage times.
And thus back to the time when we once again made mistakes in developing suitable commercially manufactured food for our cats.
The cat is an obligate carnivore and cannot synthesize essential nutrients such as taurine, vitamin A, and arachidonic acid – it is biologically fundamentally different from the dog.
Dry food is poorly aligned with the cat’s physiology, as a high starch content and low moisture content conflict with its natural prey-based diet.
The cat’s nutritional needs are evolutionarily anchored, which explains both its high protein requirements, risk of kidney problems, and selective eating behavior.
Dry food – easy, practical, and healthy?
Dry food IS easy and practical for the cat owner, but it is not health-promoting for the cat. On the contrary. Classic extruded dry food stands in direct opposition to the cat’s nutritional physiology. From a purely technological standpoint, the manufacturing process requires a certain amount of starch – otherwise the dry food kibble simply would not be able to hold its shape. The cat’s ability to digest starch is VERY limited, which is why starch in the food has virtually no nutritional value for the cat. In fact, the starch takes up space that could otherwise be used for another nutrient that is very important for the cat, namely protein. Cats have a constantly high rate of protein breakdown and a limited ability to downregulate this protein catabolism. If the cat does not receive enough protein through its diet, it will begin to use its own body proteins (i.e., muscles and organs) to maintain protein catabolism – something that can be life-threatening for the cat. Therefore, the cat has a significantly higher protein requirement than the dog, and this also applies to the senior cat. And here we are not only talking about the amount of protein, but also the quality. High protein digestibility and biological value are absolutely crucial. In practice, this means animal-based rather than plant-based proteins and as little processing of the food as possible, since processing reduces protein digestibility.
The high starch content in dry food is not the only argument showing that we humans made a serious mistake when we believed we could feed cats a starch-filled dry diet. Cats descend from desert animals that meet their fluid requirements through their food. A natural prey-based diet contains 70 to 75% moisture. Dry food contains only around 10% moisture. Although the cat no longer lives in the desert, most individuals have not learned to drink sufficient amounts of water to meet their fluid needs. If a cat is fed exclusively dry food, it will be at risk of inadequate fluid intake. It is therefore not surprising that many cats struggle with kidney disease and urinary stones – conditions that are promoted by low fluid intake. A cat that has already developed kidney disease or suffers from urinary stones must be fed a specially adapted diet. One of the most important nutritional adjustments for a cat with kidney disease is a reduced intake of the mineral phosphorus. This applies not only to the cat’s complete diet, but also to treats, snacks, and supplements. To be on the safe side, phosphorus-rich delicacies such as meaty bones and dried meat should be avoided entirely. Just 10 g of dried meat can contain up to 80 mg of phosphorus, which corresponds to 50 to 80% of a healthy cat’s daily phosphorus requirement. For a cat with kidney disease, this would mean a significant additional burden on the kidneys. Another enormously important nutritional adjustment for a cat suffering from kidney disease or urinary stones is switching it to a diet with a high moisture content. And this brings me to a well-known challenge for cat owners.
The cat is the epitome of a “picky eater”
Cats can be extremely difficult to feed – and no, it is rarely because they are spoiled or “want something better.” On the contrary, the cat’s selective eating behavior is largely a result of evolution, sensory biology, and early imprinting.
As true carnivores, cats have throughout evolution lived on a relatively narrow range of prey with consistent taste, texture, and nutrient profiles. Unlike dogs, cats have never needed to adapt to many different food sources. There has simply been no evolutionary advantage in being flexible in their food choices. This is also reflected in the cat’s senses. Cats cannot taste sweetness, but they react strongly to certain amino acids (the umami taste), fatty acids, and bitter compounds. Small changes in the composition of the food, such as the protein source, type of fat, heat processing, or early stages of rancidity, may therefore be enough for the cat to refuse to eat its food.
In addition, cats are naturally skeptical of new food, a phenomenon known as “food neophobia.” It is an instinctive protective mechanism designed to prevent the ingestion of potentially toxic food items. Adult cats in particular, and cats that have grown up on a very uniform diet, may react strongly even to small changes in their food.
A cat’s eating preferences are shaped early in life. Taste, smell, and texture from the mother’s milk and the diet during the kitten period create a relatively narrow “acceptance window” that often follows the cat for the rest of its life. Cats that have received only one type of food as kittens therefore often become more selective eaters as adults. For this reason, it is extremely important to accustom kittens to a wide variety of different types of food.
With this knowledge, it makes perfect sense that it is not so simple to switch a cat that has eaten dry food its entire life over to a more moisture-rich diet. It may well take several months to complete a dietary transition in a cat. In the meantime, one can try to encourage the cat to consume more water in other ways.
Tricks to get the cat to drink more
When dealing with an animal that does not drink, not because it does not want to, but because it is biologically not designed to meet its fluid needs through drinking water, one has to be a bit creative when it comes to the whole “drinking topic.”
Most cats do not like having their water bowl placed right next to their food bowl. There is a good evolutionary reason for this. Stagnant water close to the “prey” can easily be contaminated and lead to illness in whoever drinks from it. Therefore, it is a good idea to place several water stations around the home and at a good distance from where the cat “takes down its prey,” aka the food bowl. Also remember to change the water regularly so it is always fresh.
Many cats also dislike their whiskers touching the edge of the water bowl when they drink. Therefore, choose a wide and shallow bowl, preferably made of ceramic, glass, or stainless steel, as many cats are not fond of plastic. Some cats may also be more easily encouraged to drink when the water is offered from a drinking fountain.
In some cats, drinking can also be increased by adding a little flavor to the water. This can, for example, be done by adding a bit of (unsalted) cooking water from meat or fish to the water or upgrading the water with bone broth. If you use this trick, it is important to discard the remaining water mixture shortly after the cat has drunk, to avoid possible spoilage of fat or protein residues in the water and thus a change in smell and taste. This could otherwise lead to something we definitely do not want: a learned drinking aversion.
So no, the cat is certainly not just a small dog. Considering the cat’s specific nutritional needs, it is perhaps more of an advanced companion animal for “the very dedicated and motivated pet owner who is constantly looking for new challenges and never runs out of patience.”
Copyright Mandy Benning / @dex_the_shiba
Conclusion
The cat is not a small dog – neither biologically nor nutritionally. As a true carnivore, the cat has unique requirements for animal-based nutrients such as taurine, vitamin A, arachidonic acid, and niacin, which it cannot synthesize in sufficient amounts on its own. Historically, it became clear that cats do not thrive on dog food, which led to serious deficiency symptoms and disease.
The article reviews the differences between the dog’s and the cat’s metabolism, explains why dry food with a high starch content does not align with the cat’s natural nutritional physiology, and highlights the importance of fluid intake in relation to kidney health and urinary tract problems.
In addition, the cat’s selective eating behavior is explained from the perspectives of evolution, sensory biology, and early imprinting – and practical advice is provided on how to increase the cat’s fluid intake.
The conclusion is clear: The cat requires a nutritional strategy that respects its nature as an obligate carnivore – not an adaptation of the dog’s diet.
The Author: Ann-Kristin Meyer
MSc in Animal Science from the University of Copenhagen, specializing in canine nutrition, Owner of HundefoderNørden
1. Is the cat a true carnivore?
Yes. The cat is an obligate carnivore, which means it is biologically dependent on animal-based nutrients such as taurine, vitamin A, and arachidonic acid in order to survive and thrive.
2. Can cats eat dog food?
No. Dog food does not meet the cat’s specific needs for, among other things, taurine and certain fatty acids. Long-term feeding with dog food can lead to serious deficiency symptoms.
3. Is dry food healthy for cats?
Dry food is practical, but it often contains more starch and far less moisture than the cat’s natural diet. This can put strain on both metabolism and fluid balance.
4. Why do many cats drink so little water?
Cats descend from desert animals and are biologically designed to obtain most of their fluid through their prey. Therefore, they do not naturally compensate by drinking more water. Adding flavor to the water—such as a small amount of unsalted cooking water from meat or fish—can help increase intake, and bone broth can also be a great option to encourage hydration.
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