Dogs and cats have unique nutritional needs. High quality foods are specifically tailored to the dietary requirements of the intended species. Therefore, it is not wise to feed an exclusive diet of dog food to cats, nor cat food to dogs.
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. For more information on keeping your pets from eating each others’ foods, click here.
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.