Why cats are not small dogs: nutritional requirements of cats

Cats have very specific nutritional requirements that are sometimes forgotten when choosing pet food. New cat owners or people who have only ever owned dogs, might not know how unique cats actually are and why they are not small dogs. Sometimes it’s easy to think all small animals are the same and should be fed the same; to the untrained eye a kibble diet can look the same regardless of whether it’s for a cat or dog, but that doesn’t mean the content is the same.

In recent times, we’ve become more aware of cats nutritional requirements – with the addition of taurine to pet food in the mid 90’s, as an example. Cats are obligate carnivores, which means their diet requires nutrients found only in animals. This doesn’t mean, however that they cannot eat any plant matter, it just means that meat needs to be present in the diet in sufficient amounts to provide for their nutritional requirements. This is the main way that cats differ from dogs – dogs are from the Order Carnivora, so many people mistake this to mean they are carnivores, however are actually classified as omnivores. Even some bears and other animals that fall under the same Order Carnivora, are omnivores (some are even herbivores!). So despite having some things in common, feeding a dog food to a cat could have detrimental effects to their health.

So why can’t I feed dog food?

Let’s first look at some of the nutrients that only cats need, and dogs do not.

Taurine: the very first nutrient that springs to mind is taurine. Taurine is an amino acid which in dogs, can be synthesized from methionine and cysteine. In cats, this doesn’t happen and taurine must be present in the diet to allow the cat to satisfy their needs for it. Taurine is only present in meat, which is another reason cats need meat in their diet – unlike dogs, who can make their own and do not need this in their diet, thus can get by without a high meat content in their food. Taurine is vital for vision, cardiac function and nerve function.

Arginine: another amino acid that cats cannot make is arginine. Most other animals can synthesise some arginine however cats entirely lack the enzyme required to make it. This amino acid plays a role in the urea cycle, by removing the ammonia created as a by-product of protein breakdown. When ammonia builds up in the body, it can cause neurological signs, vomiting, weight loss and death.

Vitamin A: In cats, the enzyme that makes Vitamin A is fairly inactive so they cannot make enough to satisfy their requirements without supplementation. Other animals can synthesise Vitamin A from leafy greens and carrots.

Vitamin D: Cats and dogs are both unable to make enough of their own Vitamin D, therefore both cat and dog food will contain vitamin D supplements. However the difference between dogs and cats is that cats cannot make use of the plant form of Vitamin D, so their diets must contain the animal form of the vitamin (D3) as opposed to dog foods that may contain one or both.

Arachidonic acid: This essential fatty acid cannot be synthesized by cats and is only found in animal fats, so must be present in the diet. Cats fed a diet deficient in this fatty acid can develop poor reproductive performance, fatty liver disease, hyperkeratosis of the skin and excessive fat in the kidneys.

Can I feed my dog, a cat food?

As previously covered in my blog post about nutrient excesses, dogs can be susceptible to nutritional diseases if fed a cat food aswell. As dogs can synthesise Vitamin A themselves, they can suffer from hypervitaminosis A if fed a cat food. As they can also make use of the plant based vitamin D2, they can experience excesses of vitamin D from cat food, which the symptoms of are still fresh in alot of people’s minds after recent recalls. Essential fatty acids such as arachidonic acid don’t typically cause issues on their own being excessive, but can interfere with the absorption of other nutrients in the diet thus creating other issues.

What about foods designed to be fed to dogs and cats?

A few foods market themselves as suitable for both cats and dogs. If we think about it in the way of ‘all life stages’ diet, the food would need to be created to meet the requirements of the most demanding nutritional state. In this case, it would need to meet the cat’s requirements first and foremost, as they will die without the nutrients we’ve mentioned above. Dogs, given they are omnivores, can generally cope fairly well with different nutrient profiles so would be able to handle a food that was designed for cats and dogs – however, this is not to say it’s recommended. As we discussed above; the food would need to meet the cat’s requirements first, so it’s really considered a cat food therefore it would be excessive for the dogs requirements. For this reason, feeding a diet that is for both species is only recommended in the short term, never the long term – and the diets I was able to locate, such as recovery foods that are labelled for cats and dogs both advise it is for short term or intermittent feeding only.

If you want a diet you can feed both cats and dogs for convenience and money-saving, it’s important to remember these two species have alot of differences and it’s more important to address their needs nutritionally – if we put convienience ahead of health, we are likely to run into problems down the track that will work out more costly than feeding an appropriate food. A better idea is to feed both pets the same brand of food, if feeding a commercial food as you may occasionally get loyalty discounts if you buy more than one bag. If home cooking, formulate a recipe through BalanceIT.com for them both with similar ingredients so you really only need to adjust the amounts and use the appropriate supplements for their species.

Of course, there are foodstuffs that both dogs and cats can eat, and particularly where treats or toppers are concerned you generally can feeding similar things in that case, particularly if it’s not the pet’s entire diet.

The key takeaways here are that cats are unique, and trying to address the needs of more than one species is not ideal for either pets. Always choose a food that meets both of your pet’s individual needs and is safe for long term feeding.

Have you ever used a diet for both/multiple species? Let us know in the comments below!

If you found this post helpful and informative, please consider making a small donation via buymeacoffee. The proceeds help me continue to provide educational materials for veterinary professionals and pet owners.


MacDonald ML, Anderson BC, Rogers QR, Buffington CA, Morris JG. Essential fatty acid requirements of cats: pathology of essential fatty acid deficiency. Am J Vet Res. 1984;45(7):1310-1317.




One thought on “Why cats are not small dogs: nutritional requirements of cats

  1. Pingback: Fresh foods for pets: is it better? – nutrition rvn