October 16, 2005
Fortify The Food Bowl For The Aging Canine
Although owners often may feel helpless as they witness the effects of aging on their geriatric canine companions, the fact is they have several occasions to make a difference. For example, every time your older dog comes to the sound of the can opener or the food scoop, you have an opportunity to impact its health and well-being. The choices made during feeding time, including the amount and kind of food and the supplements (if any) chosen to augment the diet, can enhance a dog’s ability to deal with the conditions of aging.
Current veterinary and nutritional thinking indicates both older dogs and younger dogs in fact do have different nutritional requirements than adult maintenance diets provide. Nutritional needs vary greatly depending on breed, age, size, physiologic state, stress and activity level, and even the unique biochemical individuality of each dog. Two nutritional paradigms are worth remembering:
- The optimal range for a given nutrient is relatively broad for the healthy adult dog.
- The optimal range narrows as conditions such as growth, stress, disease, exercise, cold climate, etc., become more demanding.
Part 1 of this series looked at the effects of aging on the various body systems; Part 2 examined the common chronic ailments of old dogs. In this third part, we will synthesize the two previous articles and explore not only the nutritional requirements of the older dog but also how good nutrition can forestall or ameliorate the common ailments of old age. We will attempt to separate fact from fiction as we explore the various options available to owners of geriatric dogs while remaining mindful that there are more geriatric foods than geriatric studies.
The Aging System
A whole-body approach looks at resting metabolic requirements, thermal environment (i.e., hot, cold or thermo-neutral) and activity levels. This sounds simple enough, but there are complications. Body systems in the older dog don’t work as well as they did when it was young. Although the ability to ingest, chew, digest, absorb and excrete does not depreciate significantly in the elder canine, the dietary requirements do change and so does the ability of the various body systems to filter or metabolize the nutritional inputs.
For example, through digestion and absorption, the older dog can extract the same amount of protein from a given food as when it was young, but once extracted, its body cannot use it as efficiently as it once did. Any accurate determination of geriatric nutritional requirements must consider these factors.
In general, the elements that contribute to the problems associated with aging are the accumulation of cellular damage due to free radicals, impaired protein synthesis, the decreased rate of DNA repair and decreased cell division. The geriatric canine also has lowered energy requirements due to its diminished activity levels and reduced lean body mass. The onset of geriatric behavioral problems, collectively referred to as cognitive dysfunction, also need to be addressed.
With these points in mind, we will present the changing nutritional needs of this particular population and will discuss specific nutritional strategies that have been found to moderate or manage those diseases most common in the aging animal.
First we will take a quick look at the energy requirements needed to keep the old pooch running at full steam. Nutritional minimums were developed as early as the 1940s by the National Research Council of the National Academy of Sciences.1 Since then, controlled studies done by the major dog food manufacturers have been codified into nutrient profiles by the Association of American Feed Control Officials.2
Although the nutrient profiles are a good starting point for developing diets, the big players do much fine-tuning because they can afford to conduct long-term feeding trials. Thus, for example, the Iams Co., Hill’s, Pedigree, Ralston Purina Co., etc., all have slightly differing energy requirement determinations based on their own formulations. The point to remember is that the variance among the studies is less than the variance among individual dogs in any study.
A 1991 study found that dogs 8 to 10 years of age require daily energy intakes of about 80 percent of 1-year-old dogs.3 Repeated studies documented similar relationships.4,5 In the words of Dr. Avi Deshmukh, a food regulator at Ralston Purina, “Feed the dog, not the bowl.” That is, use one of the body condition scoring systems (which include profiles for healthy, overweight and emaciated canines) to evaluate whether your dog is too thin, too fat or just right.6 Feed thin dogs more, fat dogs less. It is as simple as that.
For most, commercial “senior” or “geriatric” foods (too numerous to list here because almost every major manufacturer produces one or more formulas tailored for the older dog) are very satisfactory. In the event of serious health problems tractable with nutritional support, we suggest you discuss your dog’s possible need for a special diet with your veterinarian. Table 1 demonstrates the many nutritional options available.
Some Nutritional Guidelines
Remember as you read food labels and consider your dog’s lifestyle and ideal weight that there is no one best way to feed the older canine. Geriatric dogs are a diverse group and are best fed as individuals. Their dietary needs, however, reflect the gradual loss of their ability to maintain nutritional reserves. Because of certain biochemical requirements, the healthy geriatric dog requires about 50 percent more protein than the young adult, and depending on the quality of the protein, it should make up 20 percent to 30 percent of the total calories ingested.
Until recently, protein restriction was recommended in an effort to protect renal function. Limiting protein fails to prevent urinary filtration problems associated with glomerular hyperfusion and hypertension in the nephrons (where filtration occurs). Indeed, newer research shows dietary protein is not detrimental to kidney function.7 On the contrary, protein restriction can result in impaired wound healing, diminished immune function and lowered enzyme activities and cellular turnover. Those dogs with impaired renal function do better with dietary phosphorus restriction; however, limiting this mineral is unlikely to delay the onset of renal disease or to benefit healthy geriatric dogs.8,9
It has been suggested that moderate increases in B vitamins and vitamins E and D are appropriate for the geriatric dog; however, this remains controversial.10-12 Specific to the normal geriatric canine, higher than adult-maintenance-level B complex ( B1 , B2, B6), folic acid and B12 are indicated for stress, allergies and infection and are essential for a healthy immune system and energy production.
Similarly, higher than adult-maintenance-level anti-oxidants vitamin E and ester-C and the minerals selenium and zinc are recommended for their role in immune function. Other nutritional supplements include digestive enzymes, coenzyme Q10, some source of omega-3 and omega-6 fatty acids (such as ground flax seeds which maintain skin and coat condition and can short-circuit the inflammatory process often associated with the formation of free radicals) and dimethylglycine, which promotes metabolism by enhancing oxygen usage and may improve immune response. For cognitive function, supplementing with gingko biloba may be useful because it increases the blood circulation to the brain and has been shown to increase the release of a variety of neurotransmitters essential to communication within the brain.13
By Susan Thorpe-Vargas, Ph.D. and John C. Cargill, M.A., M.B.A., M.S.