Published by: Ingrid King. Last Updated on: June 26, 2023 by Crystal Uys

a ragdoll cat eating from a glass bowl

Written by Elizabeth Colleran, DVM

The nutritional requirements of senior cats are unique when compared to those of humans and dogs. Elderly cats require more energy to maintain their body weight, in part because their fat and protein digestion is impaired. To compensate for impaired nutrient absorption, senior cats need to eat more food relative to their body weight than younger cats. This can be challenging as aging changes associated with decreased ability to smell and taste can cause appetite to decline. Additionally, many aging conditions in cats result in pain, which can also distract from interest in food at a time when more food is essential.

What is a hypercarnivore?

The whole cat family, from the California mountain lion to Felis nigripes, the tiny black footed cat of Africa, are hypercarnivores. At some point, millions of years ago, the ancestral cat became such a specialized meat eater that it lost the ability to live on plants. Many of the cat’s relatives in the animal kingdom are actually omnivores, even though they are referred to as Carnivora. Domestic dogs, foxes, and bears have evolved to be omnivores. Some, like pandas, have reverted to being vegetarian.

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Why cats need protein

Dietary protein supplies amino acids and is needed for the manufacture of antibodies, enzymes, hormones, and tissues. It provides energy and is essential for growth and development. Protein derived from meat and poultry contains ample amounts of these essential amino acids. While vegetable and grain based proteins provide amino acids, cats, unlike dogs and other omnivores, lack the enzymes required to process them metabolically.

Cats either never acquired or lost this ability to use plants for energy during their evolution – a kind of nutritional dead-end. They require far more protein in their diet because they get most of their energy not from carbohydrates but from protein. Other animals, faced with the shortage of protein in the diet, can channel all the protein they get into maintaining and repairing their bodies but cats cannot.

None of this is a problem if the cat can get plenty of meat in her diet.

Wild cats automatically eat a balanced diet

For most of their coexistence with humankind, cats were valued primarily for their skill as hunters. Since mice contain all the nourishment the cat needs, a successful hunter automatically ate a balanced diet. Now cats depend on their humans to provide a complete and balanced diet composed of some unique nutrients, like taurine, only required by the hypercarnivore.

Our most powerful tool to keep cats healthy as they age is to know what they’re eating. Recent data suggests that cats need a diet that is 40 – 45% protein on a dry matter basis. The protein must come from a highly digestible source, and that means meat. Because canned food contains a great deal of moisture, the protein percentage will look quite small unless it’s calculated on the basis of dry matter. Learn to read labels and call companies if you can’t find the information you need.

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Dietary protein and cats with kidney disease

Not long ago, it was thought that protein restriction might help preserve failing kidneys in senior cats. There were some research studies that showed that. Unfortunately, this research did not take place long enough to evaluate the effect on the whole cat. Protein restriction causes muscle wasting, a condition called sarcopenia, which is associated with decreased longevity and quality of life. We know now the cats will use amino acids in their own muscle if the inadequate protein is fed.

There may be some benefit in the late stage kidney disease, but by then cats are usually quite finicky, making diet changes difficult. There are other ways to preserve the aging kidney.

Is your senior cat getting adequate nutrition?

Your hands and eyes are crucial tools to assessing your cat’s nutritional well-being. Even if you’ve been told your cat is overweight, run your fingers over the top of his back, along the spine. If you can feel the bones like pebbles lined up evenly down the back, your cat is losing protein from his body and needs more in his diet. Check the crown of his head. If you can see a bony crest there, it is a sign of serious muscle loss. Lastly, if you can see or feel the long femur bone of the back leg, the one between the hip and the knee, muscle is disappearing.

Some of this information may run counter to what you’ve been led to believe by pet food companies marketing lifestages and lifestyle diets for senior cats. If you need help determining the best diet for your senior cat, I recommend finding a veterinarian with a keen interest in feline nutrition to guide you.

bowl of wet food on the floor near cat looking up
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Dr. Elizabeth Colleran is a 1990 graduate of Tufts University School of Veterinary Medicine. She holds a Masters of Science in Animals and Public Policy, also from Tufts University School of Veterinary Medicine. In 2011, she was the President of the American Association of Feline Practitioners (AAFP). She is a Diplomate of the American Board of Veterinary Practitioners, Specialty in Feline Practice. As the spokesperson for the AAFP initiative Cat Friendly Practice, she speaks at major conferences around the country. Dr. Colleran owns the Chico Hospital for Cats in Chico, CA and the Cat Hospital of Portland in Portland, OR.

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