Abstract

Senior Cat Physiology

Chronic dehydration can exacerbate disease and even reduce the cat's ability to regulate body temperature. (Hand, Thatcher, Remillard, and Roudebush, 2000)  Digestibility also affects food intake in older cats and decreases by about 10 percent by the time a cat reaches age 14. (Buffington, Holloway, and Abood, 2004)  Dental problems are quite common and can lead to a lack of appetite, weight loss and abnormal chewing and swallowing behavior.  In the worst cases the issues above combine to lead to anorexia and/or dehydration.  Oral examinations and the treatment of oral cavity disorders should not be overlooked during regular veterinary visits for they are often one of the greatest contributing factors to morbidity in geriatric cats. (Wolf, 1999)  Decreased immune response, decreased glucose tolerance, decreased renal function, and several other changes commonly develop with age.  However, not all cats will experience these age-associated changes and different rates of aging will occur. (Hand et. al, 2000)

Healthy Senior Cats and Disease Prevention Through Diet

Some veterinary experts suggest that due to the lack of studies on nutrient requirements of cats in the last third or quarter of their lives, we must base our decisions on dietary history, a physical exam, and diagnostic testing.  They recommend diets that have been "made reputable" by manufacturers and approved by the American Association of Feed Control Officials (AAFCO). (Buffington, et. al, 2004)  Perhaps the most helpful advice Buffington and associates offer is to monitor your senior cat's food intake as changes in food intake often serve as a "warning system" or signal for health problems.  This is because decreased food intake is a common symptom of disease and illness.  They also encourage adequate fresh water intake.  There is some consensus that dietary protein need not be restricted in the healthy older cat and that dry foods designed for tartar removal or teeth cleaning can improve oral health. (Hand et. al, 2000)

Veterinarians have yet to develop a "one size fits all" senior cat diet.  The task is merely impossible given the enormous diversity of senior cats and their varying health issues.  However, some recent studies have shown what not to feed your cat.  A 2003 study published in the Journal of Feline Medicine and Surgery proved that healthy cats fed homemade diets consisting primarily of oily fish became depressed, experienced lack of appetite, leukocytosis, anaemia, subcutaneous nodules, and developed Pansteatitis (a disease related to fish-based diets)  which is caused by the consumption of high levels of unsaturated fatty acids and/or the insufficient intake of vitamin E, leading to inflammation of adipose tissue.  This is a case of diet contributing to or even causing disease.

Matching Diet To Disease:

Obesity and Diabetes

The veterinary nutritional expert quoted in the Wolfson article recommends that what cat guardians should look for on supermarket shelves are diets that are meat based, canned or wet foods because they are higher in moisture than dry cat foods, and foods that mimic an "all-prey" diet.  A typical mouse contains 65-85 percent moisture versus typical dry cat foods that contain only 10 percent moisture.  Dry foods can contain up to 50% carbohydrates while a mouse generally contains less than 10 percent. (Wolfson, 2004)  Extra carbohydrates mean extra calories and weight gain for most sedentary older cats ages 7-12.  Excessive feeding of any food will not result in effective weight control.  Yet just like humans, each cat is different and a diet that is right for one obese older cat may be wrong for another. 

Some of the confusion over diet advice may be based on the fact that we are often told that "geriatric" cats need more calories.  The problem lies with the definitions.  Generally, older cats between the ages of 8 and 12 tend to grow heavier and after age 12 tend to become thinner and metabolically old. (Pavia, 2004)  Strategies to increase calories in a healthy way for thinning cats well into their senior years include buying cat foods with higher protein content and cat foods that are used for growth. (Deneen, 2004)  Some studies also show that decreasing fat content may improve insulin sensitivity.  Impaired glucose tolerance is often age related and can be controlled by decreasing carbohydrates and fat content in the diet. (Rand, Farrow, Fleeman, and Appleton, 2003) 

Other recent studies with promising results for the treatment and prevention of obesity and diabetes in cats include cat foods with added supplements of vitamin A, chromium, and carnitine.  Studies to determine the appropriate fiber content of cat foods have been inconclusive and contradictory. (Rand et. al, 2003)  Reading cat food labels carefully and visiting a veterinarian for geriatric laboratory tests to determine a cat's ideal weight and diet are wise decisions.  Once you and your veterinarian have decided on the best diet for your older cat, the cat's diet must be adjusted gradually and carefully.  How to properly go about making adjustments to your senior cat's diet will be discussed later in this paper.

Hyperthyroidism

Kidney Disease

Adjusting the Diet

One 2001 study concludes that smell is the primary factor influencing food preference although cats will make decisions about food based on both smell and taste.  Diets having one dominant taste (versus a mix of different flavors)  resulted in a higher feed intake. (Hullar, Fekete, Andrasofsky, Szocs, and Berkenyi, 2001)  Other studies show that sick geriatric cats benefit from being petted while they eat, wider and shorter bowls, warming and moistening the food, and feeding favorite foods.  Another consideration is that for cats on medications, dietary intake and nutritional requirements may be affected by interactions between drugs and certain nutrients.  It's also important to note that for a sick cat that is supposed to be on a veterinary prescribed diet, it is better for the cat to eat something than nothing at all if the prescribed diet is rejected. (Buffington et. al, 2004)

Quality Standards

Preservatives

On the other end of the debate are veterinarians and researchers who warn that the lack of preservatives, or so-called "natural" preservatives may cause food to become rancid more easily.  Rancid cat food has been linked to cell abnormalities that lead to cancer. (Bonham, 2004)  Bonham also points out that canning seals in freshness and therefore usually requires less preservatives than other types of packaging.  She concludes that fresh is always best and that food sensitivities are more likely due to protein or grains than preservatives in amounts as miniscule as those found in most commercial cat foods (around 50 parts per million).

Conclusions

Based on the journals, books, and articles summarized in this paper, it seems appropriate to conclude that for healthy cats of all ages: the current trend toward meat-based, high moisture or wet food diets with higher protein and lower carbohydrate content, or diets that imitate the moisture and nutritional content of a cat's typical prey, seem to be gaining a high level of acceptance among many veterinary nutritional experts.  It is clear that more research is needed to determine the specific nutritional requirements of senior cats.  Perhaps consumer demand for products specialized for the geriatric cat will drive this research as the cat becomes more popular, gains higher status as a pet, and the cat population continues to age.

References