Cats and dogs can and will eat each other’s food if given the chance. But should they?
This is a common question I get as a Vet from a lot of dog and cat households.
The simple truth is that it highly depends on how often and how much of each other’s food they are eating.
In this article, I’m going to explain the difference between dog and cat food and how to keep keep your dog away from cat feeding bowl.
What is the difference between dog food and cat food?
But first, storytime: as a student vet in the ICU of a veterinary hospital, I frequently saw the magic of cat food work before my very own eyes.
Exhausted, emaciated, skeletal dogs, who would refuse any kibble, tins, and even extra special treats we tried to feed them, would suddenly look 5 years younger at the very whiff of cat food.
Cat food helped them put on the few lifesaving pounds they needed to survive their illnesses. How was this possible? There must be something in cat food that makes it so irresistibly appealing to our canine companions!
Before we get to the nitty-gritty of cat food contents, it’s important to understand some of the things that make a dog different from a cat. One of the major differences between cats and dogs is their intestines.
Cat intestines are relatively short and very inefficient when compared to those of dogs. This results in a lot of nutrients passing through the digestive tract intact, without being absorbed. 
As you can imagine, this makes for some pretty nutritious cat poop, but then how do the cats manage to get their nutrition?
In order to make up for this inefficiency, cat food has to be high in both proteins and fats- a quick glance at any pair of dog and cat food labels will show this.
Unfortunately, these two components are irresistible to our greedy, gorging dogs. Here’s a fun fact about why fast food is so addictive to humans: human brains are wired to crave food with high sugar and salt content.
This is because, back when humanity was first evolving, it was difficult to obtain enough of those nutrients.
For very similar reasons, dogs are hardwired to seek protein and fat.  This often leads to them being obsessed with their feline housemate’s food and quite often, unfortunately, also their litter box. [3, 4, 5]
Is it really that different? Is cat food bad for dogs?
The answers to those questions are:
“Different enough to make a difference” and “Can be if fed regularly”?
As illustrated in the charts below the differences are obvious.
There is no need for alarm if your otherwise healthy dog ate your cat’s food. Immediate effects on dogs that eat cat food can be stomach upset, vomiting and diarrhea.
While this does not mean that your dog will drop dead after eating cat food, with time, regular eating of cat food will lead to obesity due to cat food’s high-fat content.
The fat content in cat food might also lead to pancreatitis if dogs are fed cat food as their main diet for an extended amount of time.
Eating cat food is particularly harmful to dogs that suffer from liver and kidney conditions. This is because the high protein levels in cat food will cause further stress on the already diseased liver and kidneys, and can lead to rapid deterioration of your dog’s condition.
You need to understand that the damage done by cat food is cumulative. In healthy dogs, you will start seeing the serious symptoms after being negligent for some time. [1, 6]
Can my dog’s food harm my cat?
Having said that, it is far more harmful when cats eat dog food as their main diet than the other way round. Dog food is very unsuitable for cats when fed on its own.
Cats need their food to contain enough Vitamin A, Niacin, Arachidonic acid and Taurine. This is because cats, unlike dogs, are obligate carnivores, and either completely lack the capability or cannot produce enough of these essential vitamins, fatty acids and amino acids by their own means.
However, you should not be alarmed if your cat eats some of your dog’s food. Cats can eat dog food in small amounts as long as it is not their main diet.
Cats need a specifically formulated certified cat diet that contains enough protein, fat and the above essential vitamins, fatty acids and amino acids to live a long and healthy life. 
What can I do if my dog ate cat food?
This question depends on where the dog found cat food. If you catch your dog eating your cat’s food, your main worry will be devising some ingenious plan to keep your cat food burglar away from Felix’s food.
However, if dogs and bad individuals know one thing, it is that cat food is tasty. If your dog finds and eats cat food outside, make sure that the food contains no poison.
Cat food and other tasty food items are often used by nasty individuals to poison animals. If you can’t see anything strange in the cat food, take your dog home and keep an eye on them for the rest of the day.
If they start behaving or if the cat food contained something strange, we suggest you take your dog to the nearest veterinary clinic immediately.
Take some of the food found to the veterinarian so they can identify the toxic substance quickly.
So what can I do to keep Dogin Hood from raiding the cat food bowl?
First thing to do is to take a good look at your dog. The measures you will have to take for a Yorkie will be different from those you will take for a Great Dane.
If you have a small dog, usually putting the cat’s food on an elevated place will do the trick. Some dogs find ways around this and move furniture around. Make sure that they cannot play tetris with the furniture and build themselves a stairway to your cat’s coveted food.
If high places work for small dogs, small spaces usually work for big dogs. You can put your cat’s food in a small traveling crate that is just big and comfortable enough for your cat to eat their meal in peace.
Big dogs can however tople such small traveling crates. Find a way how to fix the crate so it cannot be moved about.
You can also put your cat’s food in a closed room and install a cat flap that your dog could not fit through.
Dedicating an area in your house where your cat can have some down time away from your dog is also beneficial for your cat as felines get stressed easily. Stress can sometimes lead to some serious health conditions in cats.
You can also put your cat’s food in a particularly challenging place. Healthy cats are like ninjas, reaching their food bowl on a high shelf shouldn’t be an issue.
Luckily dogs aren’t as nimble as cats. It is always good to put your cat’s food where it would require a great feat of athleticism on your dog’s part. If they are so intent on getting to it the least you can do is make them work for it.
The bottom line
We hope that you can now appreciate what makes dog food and cat food different. Keep in mind that while cat food is not poisonous to dogs and vice versa, frequently eating significant quantities of each other’s food can lead to serious health conditions over time.
Use the above tips to keep your mixed household away from each other’s food and keep your pets healthy.