I've read somewhere

• Dog food is high in Vitamin A when compared to cat food.
• Taurine is an essential component in a cat’s diet lack of it can lead to problems of the heart, respiratory tract and blindness. Not needed for dogs.
• Cat food contains and needs Arachidonic acid.

So my understanding is that dogs can survive (I don't say thrive) on cat food but not vice versa. Cat food is far more expensive though. When it comes to cats you may find Feeding Your Cat: Know the Basics of Feline Nutrition to be an interesting read.

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