Mature adult and senior cats have changing dietary needs, and it is extremely important to provide guidance on daily feeding amounts. DER for mature adult cats (aged 7–10 years) may be equivalent to RER, although adjustments should be made based on the needs of the individual patient. For senior cats (greater than 10 years of age), the RER will need to be multiplied by a factor of 10–20%, and in some cases as high as 25%.¹⁰¹ Senior cats may also experience a reduction in digestive capabilities, leading to decreased BCS and thus increased caloric intake.⁹² Being underweight is a common problem in senior cats.^102–104 Prescription therapeutic diets may be indicated more often for cats in the mature adult or senior life stage for a variety of reasons (e.g., chronic kidney disease, obesity, hyperthyroidism, chronic enteropathies, osteoarthritis). If a dietary change is indicated, offering the new diet in a separate, adjacent container (rather than removing the usual food and replacing it with the new food) will permit the cat to express its preference. Dietary changes should be implemented in the home setting rather than in the practice in order to avoid stress-related food aversions. However, introduction of novel diets to inappetent, hospitalized cats should not be avoided if food consumption is a concern.

There is a lack of consensus regarding optimal dietary protein levels in mature adult cats. A published study demonstrated that aging cats should in fact receive diets higher in protein to avoid loss of lean muscle mass.¹⁰⁵ Healthy mature adult/senior cats should not be protein restricted; a diet with a minimum protein allowance of 30–45% dry matter is considered to be moderate protein and is recommended. However, cats with chronic kidney disease may benefit from prescription renal diets, which have restricted, high-quality protein and restricted phosphorus levels, as well as other ingredients that may promote renal health. Ongoing research is examining the role of antioxidants in the progression of renal disease; one study demonstrated the benefits of feeding a diet with highly bioavailable protein supplemented with fish oil, L-carnitine, antioxidants, and amino acids to senior cats in early renal failure.¹⁰⁶ Further studies are needed to develop definitive recommendations.

Some cats seem to have preferences with regard to their drinking habits, a predilection the practitioner or owner can evaluate. Water-related factors to consider include freshness, taste, movement (e.g., provided by water fountains, dripping faucets, or aquarium pump– bubbled air into a bowl), and shape of container (some cats seem to resent having their vibrissae touch the sides of the container when drinking). As with foods, changes in water-related factors should be offered in such a way that permits the cat to express its preferences. Additionally, water bowls should be cleaned regularly, as should food bowls. Diets higher in water content, such as canned foods, may improve overall water intake.