Cats, as obligate carnivores, are unique among companion animals in their need for large amounts of dietary protein (1-3). We have abundant evidence that most cats, but especially those with hyperthyroidism, should be fed a high-protein diet. In the wild where cats can choose what prey they eat, they would normally ingest at least 50% of their daily calorie needs as protein.
What happens to daily energy and protein requirements for cats as they age? While maintenance energy requirements decrease as cats mature and become middle-aged, 4-9 years of age, energy requirements sharply and progressively INCREASE again in these cats when they become older, starting at 10 to 12 years of age (17-19). If daily caloric intake is not increased, progressive weight loss will result, due in large part to the loss of lean body mass (i.e., muscle mass).
As cats age, they absorb and metabolize protein less efficiently — therefore, it’s extremely important to feed high-quality protein (i.e., animal source rather than grain-based), as well as an adequate quantity of protein to aging cats.
It’s very clear that not all proteins are created equal, especially when feeding a obligate carnivore, such as the cat (9,27). The biological value of a protein is a measure of that protein’s ability to supply amino acids (especially the 11 essential amino acids) and to supply these amino acids in the proper proportions. It is well-established that animal proteins (e.g., meat, meat by-products) have a higher biological values than vegetable proteins (e.g., corn gluten meal, soybean meal, soy protein isolate).
In the short digestive tract of cats, plant proteins are far less digestible than meat proteins. These issues are important when selecting a food for any cat, but they become of utmost importance when selecting a diet for the geriatric cat. Therefore, grain-based proteins should never be used as the primary protein source in geriatric cats.
The dogma that all older cats be fed reduced energy “senior” diets must be questioned based on what is now known about the increasing energy requirements and nutritional needs of older cats (23,24).
Excerpted from: Insights into Veterinary Endocrinology: Optimal Protein Requirements for Older Cats, Dr. Mark E. Peterson http://www.endocrinevet.info/2011/11/optimal-protein-requirements-for-older.html