Finding The Right Diet For Your Pet

06/11/2011 12:05 pm ET | Updated Sep 28, 2011

Dogs and cats need 22 amino acids to be healthy.

Pets get amino acids from the protein they eat. And the quality and quantity of protein is extremely important for carnivores -- it's the very foundation of their health.

Not All Protein is Created Equal

Protein quality is extremely variable. There are highly assimilable and digestible proteins (proteins your pet's body can easily absorb and make use of) and there are proteins that are wholly indigestible. For example beaks, feet, hides, tails and snouts are 100 percent protein, but all 100 percent is indigestible.

All protein has a biologic value, which is its usable amino acid content. Eggs have the highest biologic value at 100 percent. Fish is a close second at 92 percent. Feathers, as you might guess, have zero biologic value. They are all protein, but they are neither digestible nor assimilable.

Now there are some foods high in protein that are not species-appropriate for dogs and cats. Soy is a good example, with a biologic value of 67 percent. Many popular pet foods contain soy as a protein source, as well as corn. This is an inexpensive way for pet food manufacturers to increase protein content on the guaranteed analysis printed on the label.

Digestion and assimilation are not measured for pet foods, so manufacturers can include protein that has no biologic value for the species of animal eating it (this is also why melamine was added to pet foods that killed thousands of animals). You can be fooled into thinking you're feeding your pet high-protein food, when the reality is that the protein isn't biologically appropriate for your animal.

Rendered Pet Food -- Really Bad News

Asking a dog or cat's liver and kidneys to process low-quality, indigestible protein over a long period of time is exactly how protein in pet food got a bad rap.

In the 1940s and 1950s, pet food companies took all the pieces and parts left over at slaughterhouses, mixed them with discarded vegetables and grains not fit for human consumption, added a synthetic vitamin-mineral supplement and called it pet food.

While there was a fair amount of protein in pet food back then, the quality was terrible. Since the protein was so difficult for dogs and cats to digest, pets' kidney and liver function suffered as a result. Because of this, veterinarians began to recommend lower-protein, senior pet foods.

Therefore, I recommend if you're feeding your animal a rendered pet food, you reduce the amount of protein that you're giving him or her.

Your Pet's Protein Requirement Increases with Age

The good news is that the quality of pet food has increased dramatically in the past 30 to 40 years.

In 1992, Dr. Delmar Finco, a veterinary nutritionist, discovered that as pets age, they require more protein in their diets. Even in animals suffering from kidney failure, restricting protein in their diets did not improve their health or length of life.

Dr. Finco ultimately discovered that it was the level of phosphorus in foods -- not necessarily the amount of protein -- that exacerbated kidney disease. Today, many veterinarians recommend feeding animals with under-functioning kidneys and livers a diet filled with good quality protein that is highly digestible and assimilable. Phosphorous intake should also be limited.

We know that cats and dogs, as carnivores, require lots of high quality protein not only to maintain good organ and immune function, but also to maintain healthy muscle mass as they go through life and the aging process.

Whole, Raw, Natural Foods Are Best

I believe that foods that generate the least amount of metabolic stress are whole, raw, unprocessed and in their natural form. These foods are not only biologically appropriate, but retain all of their original moisture.

Foods that have been dehydrated, extruded or processed can have drastically depleted moisture content. Moisture content can easily drop from 70 percent down to as low as 12 percent. Your pet's kidneys and liver become stressed due to chronic low-grade dehydration.

After eating dehydrated food, it is imperative that pets -- especially cats -- drink lots of water to rehydrate their bodies.

Appropriate Food for the Species

"Species-appropriate" for your dog or cat means food that is high in protein and low in grain content (in its natural form). Your pet is a carnivore -- dogs are scavenging carnivores and cats are obligate carnivores. Carnivores need to eat animal protein and fat in order to be healthy.

Pets eating a protein-based diet do just fine as long as it contains 70 to 80 percent moisture. When you take moisture out of high protein foods, they become difficult for your pet's body to process. Ultimately, a healthy pet diet is one that is filled with high-protein, unprocessed foods -- speak to your veterinarian before making any diet changes.