"Doctor, What Should I Feed My Cat?"

 This is a common question posed to veterinarians.  I just finished reading an excellent newsletter from Drs. Wackerbarth and Vaughan at the Hyperthyroid Treatment Center in Edmonds on feeding hyperthyroid cats.  I credit them with the following specifics and for prompting me on the subject.  For more of their information, visit them online at www.felinehtc.com.  Feeding hyperthyroid cats is similar to feeding most older cats so we can consider it in a general sense and in subsequent blogs we will look at feeding for specific geriatric diseases like thyroid disease and kidney failure.

We need to always remember that cats are obligate carnivores.  This means that they rely on the nutrients in animal tissues to meet their nutritional needs.  In the wild, a prey diet consisted of 50-70% protein,  30-50% fat and less than 2% carbohydrates.  A significant portion of their water needs were also met from their diet.  Cats are designed to use proteins and fats as energy, so they need a lot of protein in their diet.  When omnivores like dogs and humans ingest insufficient protein, they can conserve amino acids and use carbohydrates for energy.  Cats cannot switch from protein use.  When their diet is deficient in protein, they will burn their own muscle tissue for energy.

Cats also have specific amino acids that must be in their diet.  Cats don’t have the ability to synthesize arginine, cysteine, methionine, and taurine.  They must eat meat based proteins so they have the full complement of amino acids carnivores require.  Plant based proteins found in higher levels in dry foods are of low biological value for cats for this reason.

Feline metabolism lacks many of the enzymes and pathways needed to utilize carbohydrates.  They can’t store their glucose like omnivores, so they are more hyperglycemic after a meal and carbs that aren’t used are stored as fat.  Cats on higher carbohydrate diets are more prone to diabetes and obesity.

Fats provide energy and are responsible for a diets palatability.  Meat based diets with animal fat provide appropriate fatty acids and needed hormone precursors.

Animal proteins are more expensive than virtually any other ingredient in pet food.  Many canned and all dry foods include plant based proteins and not enough meat.  Whole grains, glutens, and soy are of low biologic value to the cat.  Remember that “grain-free” does not equal “carb-free”.  Potatoes, peas and soy are all “grain-free”. 

Canned foods are energy dense foods.  This is great for thin cats but can lead to weight gain.  So in heavier cats, portion control becomes more important.

So, what should we feed our older cats?

On a dry matter basis, 40%+ meat based proteins, about 50% fat, and less than 10% carbohydrates. {The Feline Nutrition Awareness Effort website has an explanation of Dry matter basis and a calculator so foods can be compared accurately.  http://fnae.org/dmb.html}

Any canned food is better than any dry food.  High quality canned foods with high levels of animal based proteins that contain little to no fruits, vegetables, or grains are the best choice.