OK, so you might argue this issue is a no-brainer. But you'd be surprised to learn just how many of my cat owners feed their precious felines dog food (and vice versa).  

That’s why it’s worth detailing the differences between the two––perhaps so that you’ll not make the mistake of allowing your cat to eat the dog food she craves ... and vice versa. 

Though it’s not so common for cats to adore commercial dog food, I have met my share. And so you know, it’s not a great idea. At least not on a regular basis and definitely NOT as an exclusive diet. Here’s why:

#1 Vitamin A must be supplied in cat food, whereas dogs can make do with beta carotene instead (their bodies can turn it into vitamin A). While some dog foods may contain additional vitamin A, many won’t have the amounts a cat requires for a lifetime of optimum health. 

#2 Taurine is an amino acid all cats require. Dogs can make their own. Many dog foods may be deficient in taurine, the result being a cat who suffers a devastating kind of heart disease called hypertrophic cardiomyopathy. This also happens when cats eat a fish-only diet, since fish meat is so deficient in this amino acid. Which is probably why you’ve heard that fish is "bad" for cats, even though it's not. Well, not unless you’re offering a poorly balanced diet. (Most commercial cat foods offer extra.)

#3 Arachidonic acid is a fatty acid dogs can build themselves, while cats need the real thing. 

#4 Protein levels are another big reason not to feed cats dog food. Though some dog foods do offer very high levels of protein, most do not reach the percentage of protein our carnivorous cats require. A lifetime of low protein may not kill your cat, but we know it’s not their natural diet and therefore can’t be a good thing.

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More common, however, is the dog that will turn up his nose at commercial dog foods but gulps down cat food with gusto. This canine penchant for cat food leads many frustrated owners to mistakenly consider feline-only diets an acceptable alternative for finicky dogs. And it’s not!

Although a dog can live on cat food alone (unlike cats and a lifetime of dog foods), it’s not considered advisable. The caloric density, high protein levels, and heavy doses of fat aren’t ideally suited to all canine gastrointestinal tracts––or to their waistlines. 

More than anything else, cat food-eating dogs tend towards the obese and suffer more gastrointestinal ailments than others. Diarrhea, vomiting and even pancreatitis (which can be life-threatening) are possible outcomes for either short- or long-term feeding of cat food to dogs. Kitten food, with its even higher protein and fat levels, is even less appropriate for dogs. 

But is a feline "snack" every once in a while going to hurt your dog? Will a doggie biscuit harm your cat? Not terribly likely. Still, it wouldn’t be at the top of my to-do list for optimal pet health. 

Dr. Patty Khuly