By Jennifer A. Larsen, DVM, PhD and Amy Farcas, DVM, MS
Vet Clin Small Anim 44 (2014) 741-759
When do our PBGVs transition from being adults to seniors? The American Animal Hospital Association suggests that dogs are considered to be seniors when they are in the last 25 percent of their predicted lifespan. The typical healthy PBGV has a lifespan of about 12 to 14 years, which means that PBGVs transition from adult to senior around 10 years of age.
How do the nutritional needs of our PBGVs change as they age? This question was addressed by Dr. Jennifer Larsen, Associate Professor of Clinical Nutrition at the University of California Davis School of Veterinary Medicine, and Dr. Amy Farcas, of the University of Pennsylvania School of Veterinary Medicine Clinical Nutrition Service. Drs. Larsen and Farcas note that older dogs may have normal physiologic changes that occur with aging and pathologic changes due to disease. Both types of changes may benefit from nutritional intervention.
Normal physiological changes associated with an aging PBGV (as well as his/her aging owner!) include changes in body composition and reduced metabolic rate. In general, older dogs have a reduced lean body mass and resting energy requirement accompanied by an increase in body fat mass. It is important to monitor body condition since obesity can exacerbate age-related diseases. Surprisingly, senior dogs have a higher prevalence of being underweight, which may be due to undiagnosed pathologic conditions. Studies have shown that senior dogs absorb nutrients as well as young dogs; however, their protein requirement increases most likely due to increased protein turnover.
Many pet food manufacturers offer canine diets targeted towards the senior population. It is important to be aware that the ideal nutritional profile of a diet for senior dogs has not been agreed upon. Thus, there is wide variation in energy density, nutrients and supplements in the senior diet.
Pathologic changes in the senior dog that may respond to nutrition include cognitive dysfunction, declining immunity and degenerative joint disease. Studies have shown that a diet enriched in anti-oxidants leads to improved behavior score, social interactions, sleep patterns, agility, learning, and recognition in dogs with cognitive dysfunction. Keeping a PBGV mentally active with games that use his/her nose may also be helpful. Dietary enrichment of anti-oxidants and vitamins also improved some aspects of immunity as measured by laboratory tests, although there was no measure of immunity of dogs against infectious disease.
The prescription for preventing degenerative joint disease in dogs is the same as for humans — maintain a healthy weight, incorporate exercise into your daily routine and eat a balanced diet. As dogs and their humans age, sarcopenia (loss of muscle mass) is a major problem that can be alleviated by meeting the requirements for protein in the diet and using the muscles. A number of nutritional supplements have been touted to be effective for treating degenerative joint disease. These include fish oils that contain long chain omega-3 polyunsaturated fatty acids, green-lipped mussel extract, glucosamine and chondroitin. Unfortunately, there is still no clear consensus for the effective dose or delivery of these compounds or method of assessment.
Drs. Larsen and Farcas note that it “should be kept in mind that each of the nutraceuticals discussed earlier for the management of age-related diseases have either an incompletely assessed efficacy or have conflicting results between subjective and objective assessments or between studies.” They conclude by saying “As dogs age, they experience a wide variety of metabolic changes that affect both structure and function. These changes may consist of normal, physiologic aging changes or may manifest as age-related disease. Screening for these changes via routine physical examination and laboratory assessment is critical to affecting the processes at stages where their courses may be altered. Accommodating the specific changes observed in each individual, rather than adopting a generic senior dog approach, will allow tailoring a patient’s treatment plan to the individual’s needs.”