Effect of Nutrition on Body Condition of Senior Dogs
Gary M. Davenport, PhD
Introduction: Aging can be described as the sum of all physiological changes occurring in the body with the passage of time that ultimately result in functional impairment and death. These progressive changes occur at the cellular and subcellular levels and express themselves through altered metabolic function, disease resistance, and body composition. Although various external factors (disease, stress, malnutrition, physical inactivity, etc.) hasten these age-related changes, research continues to focus on the specific role of dietary nutrients in modulating the adverse effects of aging. The goal is to nutritionally manage these senior pets to maintain optimal health, weight and body condition, which will enable them to live longer, healthier and more active lives.
Body Condition: It is widely recognized that body composition changes with advancing age in most species, including dogs. This age-induced change is reflected in a progressive reduction in lean body mass (muscle) and a concomitant increase in body fat. As a result, senior dogs generally have a lower percentage of lean body mass and higher percentage of body fat compared with younger dogs.1,2 Although many older dogs are overweight, age-related changes in body condition may not be reflected in weight differences between old and younger dogs. In a study involving 18 young dogs (average age 1.6 years) and 18 old dogs (average age 10.6 years), the percentages of body fat and lean mass differed significantly between the two groups even though total body weight was similar.3
Dietary Protein: The decline in muscle mass during the aging process can be attributed to lower rates of whole-body protein turnover in senior pets.4,5 Providing an adequate level of protein in the diet can help reverse this decline in protein turnover and allow for the maintenance of critical muscle protein stores. These muscle protein stores are necessary for physical activity and to supply extra protein when the animal is ill, injured or otherwise stressed. In addition, the level and source of dietary protein may directly affect age-induced changes in molecular and cellular events associated with aging canine muscle. 6
Contrary to previous beliefs, recent research has shown that dietary protein level does not affect the development of progressive renal dysfunction in older dogs.7 In fact, restricting protein in the diet may contribute to the loss of muscle mass associated with aging. In a recent study, increasing the level of protein in the diets of senior dogs increased whole-body protein accretion by reducing the rate of protein breakdown.8 These results also suggested that there may be breed-specific differences in protein metabolism within the canine species. The effect of dietary protein on whole-body protein metabolism and maintenance of muscle mass was breed-specific for both young-adult and senior dogs in the study. Increasing dietary protein level increased lean body mass in senior Labrador Retrievers but not in senior Fox Terriers.
Calorie Restriction: An optimal approach for maintaining the body weight and condition of senior dogs must also consider the metabolic alterations that develop as an animal ages. These changes can affect the utilization of the nutrients contained in the senior animalís food. In many cases, providing the older pet with a diet containing lower caloric density and fat will help prevent their tendency to increase fat stores and body weight. Results of a clinical research study showed that a weight loss program for senior dogs that included Eukanuba Veterinary Dietsģ Nutritional Weight Loss Formulaš Restricted Calorie/Canine resulted in an 11 Ė 18% reduction in body weight over a 10 to 19-week period. More importantly, the weight loss of these dogs was accompanied by a significant reduction in lameness over the course of the study.9 It should be noted that some senior pets are underweight or have reduced food intake, which would require the feeding of a calorie-dense diet to maintain healthy body weight and condition.
Glucose metabolism: Glucose intolerance, characterized by changes in the balance between blood insulin and glucose concentrations, has been observed in both aging and overweight dogs. 10,11 Therefore, dietary management of glucose metabolism is important for maintaining optimal body condition of senior dogs. Research has shown that the inclusion of digestible carbohydrate sources in the diet, such as barley and sorghum, produce the most optimal combination of glucose and insulin response after a meal based on lower postprandial increases in blood glucose and insulin levels. This leveling effect reduces the glycemic response of the diet which improves glucose tolerance and metabolism in senior and overweight animals.12,13 The inclusion of moderately fermentable fiber sources in the diet, such as beet pulp, gum arabic, and fructooligosaccharides, also lowers blood glucose concentrations compared with a cellulose-containing diet.14
Chromium, Carnitine, Vitamin A: Certain unique nutrients may also help senior pets maintain healthy body weight and lean tissue mass. Chromium supplementation has been shown to improve the control of blood glucose in dogs by increasing glucose clearance from the blood and glucose tolerance.15 This improvement is associated with an increased loss of body fat and improved or maintained lean tissue mass. Feeding a low-fat diet containing L-carnitine also allows obese dogs to lose more body fat and weight than obese dogs fed the same diet without L-carnitine.16 These dogs also retained more lean body mass when fed L-carnitine. l-Carnitine improves body condition by increasing the transport of fatty acids into the mitochondria for breakdown and conversion into energy. Finally, research has shown that dogs fed high-fat diets with extra vitamin A gained less weight than animals fed the same diet without additional vitamin A.17
Summary: Research continues to show that the nutritional requirements of senior pets are uniquely different than their younger counterparts. As a result, senior pets should be fed a diet that has been specifically formulated for their unique nutritional needs. The inclusion of these various ingredients and concepts in senior formulas can help to maintain healthy body weight and body condition of senior dogs without the need to severely restrict their caloric intake. This nutritional management approach will enable our senior pets to live longer, healthier and more active lives.
1. Davenport, G, S. Gaasch, M.G. Hayek and K.A. Cummins. Effect of dietary protein on body composition and metabolic responses of geriatric and young-adult dogs. J. Vet. Intern. Med. 2001; 15:306.
2. Hayek, MG, Davenport, GM. Nutrition and aging in companion animals. J Anti-Aging Med. 1998; 1:117-123.
3. Hayek, MG. Age-related Changes in Physiological Function in the Dog and Cat: Nutritional Implications. In: Reinhart GA, Carey DP, eds. Recent Advances in Canine and Feline Nutritional Research, Vol II: 1998 Iams Nutritional Proceeding. Wilmington: Orange Frazier Press, 1998; 353-362.
4. Williams,C.C., K.A.Cummins, M.G.Hayek, and G.M.Davenport. 2001. Effect of dietary protein on whole-body protein turnover and endocrine function in young-adult and aging dogs. J. Anim. Sci. 2001; 79:3128-3136.
5. Davenport GM, Williams CC, Cummins KA, Hayek, MG. Protein Metabolism and Aging. In: Reinhart GA, Carey DP, eds. Recent Advances in Canine and Feline Nutritional Research, Vol II: 1998 Iams Nutritional Proceeding. Wilmington: Orange Frazier Press, 1998; 363-378.
6. Huff-Lonergan, E. S. Lonergan. E. Helman, S. Gaasch, K. Cummins, M. Hayek and G. Davenport. 1999. Impact of age and diet on calpastatin and troponin-T in young and old dogs. FASEB 13:A938.
7. Finco DR, Brown SA, Crowell WA, Brown CA, Barsanti JA, Carey DP, Hirakawa DA. Effects of Aging and Dietary Protein Intake on Uniphretomized Geriatric Dogs and Cats. Am J Vet Res 1994; 55:1282-1290.
8. Davenport GM, Hayek, MG, Flakoll PJ, Firkins JL. Protein and the Aging Animal. In: Proceedings, Clinical Nutrition for the Senior Dog and Cat, Pre-Congress Symposium WSAVA 2001, Vancouver, British Columbia; August 8, 2001; 39-44.
9. Tetrick MA. Senior Dog Clinical Studies. In: Proceedings, Clinical Nutrition for the Senior Dog and Cat, Pre-Congress Symposium WSAVA 2001, Vancouver, British Columbia; August 8, 2001; 45-47.
10. Mattheeuws D et al. Glucose tolerance and insulin response in obese dogs. J Am Anim Hosp Assoc 1984; 20: 287-293.
11. Nelson RW et al. Glucose tolerance and insulin response in normal-weight and obese cats. Am J Vet Res 1990; 51: 1357-1362.
12. Sunvold GD, Bouchard GF. The glycemic response to dietary starch. In: Recent Advances in Canine and Feline Nutrition, Vol II: 1998 Iams Nutrition Symposium Proceedings. Reinhart GA, Carey DP, eds. Wilmington, OH: Orange Frazer Press, 1998; 123-131.
13. Bouchard GF and Sunvold GD. Effect of dietary carbohydrate source on postprandial plasma glucose and insulin concentrations in cats. In: Recent Advances in Canine and Feline Nutrition, Vol III: 2000 Iams Nutrition Symposium Proceedings. Reinhart GA, Carey DP, eds. Wilmington, OH: Orange Frazer Press, 2000; 91-102.
14. McBurney MI, Massimino SP et al. Modulation of intestinal function and glucose homeostasis in dogs by the ingestion of fermentable dietary fibers. In: Recent Advances in Canine and Feline Nutrition, Vol II: 1998 Iams Nutrition Symposium Proceedings. Reinhart GA, Carey DP, eds. Wilmington, OH: Orange Frazer Press, 1998; 113-123.
15. Sunvold GD. The Role of Novel Nutrients in Managing Obesity. In: Reinhart GA, Carey DP, eds. Recent Advances in Canine and Feline Nutritional Research, Vol III: 2000 Iams Nutritional Proceeding. Wilmington: Orange Frazier Press, 2000; 123-133.
16. Center SA, Sunvold GD. Investigations of the Effect of l-Carnitine on Weight Reduction, Body Condition and Metabolism in Obese Dogs and Cats. In: Reinhart GA, Carey DP, eds. Recent Advances in Canine and Feline Nutritional Research, Vol III: 2000 Iams Nutritional Proceeding. Wilmington: Orange Frazier Press, 2000; 113-122.
17. Scarpace PJ, Kumar MV, Bouchard G, Sunvold GD. Dietary Vitamin A Supplementation: Role in Obesity and Leptin Regulation in the Dog and Cat. In: Reinhart GA, Carey DP, eds. Recent Advances in Canine and Feline Nutritional Research, Vol III: 2000 Iams Nutritional Proceeding. Wilmington: Orange Frazier Press, 2000; 103-111