In short, no. If your dog sneaks a snack from the cat’s bowl every once in a while, it’s certainly not going to kill him, but feeding him cat food exclusively can have some serious negative side effects.
First off, cat food is composed mainly of animal protein, and dogs are omnivores, meaning they require vegetables in their diet as well as meat.
Secondly, cat food contains vitamin A, which dogs synthesize internally and can overdose on if fed too frequently from an outside source.
Finally, cat food has a higher content of fat than dog food. Cats require more fat in their diet than dogs, so feeding your dog fatty cat food can contribute significantly to obesity. While obesity is often considered “cute” by many irresponsible pet owners, it is just as dangerous and deadly for dogs as it is for humans.