Bottom line is - if you feed your dog exclusively cat food, it would probably eventually die of pancreatitis
(cat food is also fattier than dog food) or some other malnutrition related illness - and if you did the opposite - fed cats only dog food - they would die even faster, as their digestive systems are more sensitive and they require taurine, which is sometimes but not neccesarily present in dog food.
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also, I’ve heard that cats can eat dog food, but dogs shouldn’t eat cat food. it’ll upset their stomach. so your dog would probably get the runs.
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dog owner.

Cats most definitely cannot subsist on dog food alone. Their dietary needs are harder to meet than those of dogs. For instance, cats must consume an amino acid called taurine to prevent heart problems. Dogs do not need to consume taurine–they can synthesize it internally. Therefore, cat foods are supplemented with taurine. Dog foods generally are not.

Because dogs are natural scavengers (cats are natural predators), their dietary requirements are less stringent than those of cats. Some cat foods may, in fact, be nutritionally replete for dogs. Others are not. However, cat foods are generally richer and more fattening than dog foods. Dogs that eat cat food may gain weight or suffer upset stomachs, even if they don’t develop nutritional deficiencies.

The moral of the story is that your dog should eat dog food, and your cats should eat cat food. The simplest way to make that happen could be to end the feeding free-for-all and offer meals to your pets in separate rooms.

Finally, please note that most cats and dogs can tolerate an occasional nibble of each others’ foods. However, serious problems may occur if cats eat only dog food, or vice-versa.
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my dog eats cat food and any other food in fact!
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