Results suggest that 25% restriction in food intake increased median life span and delayed the onset of signs of chronic disease in these dogs.

Prevalence and severity of osteoarthritis in several joints was less in dogs with long-term reduced food intake, compared with control dogs. Food intake is an environmental factor that may have a profound effect on development of osteoarthritis in dogs.

Restricted feeding delayed or prevented development of radiographic signs of hip joint osteoarthritis in this cohort of Labrador Retrievers. Lifetime maintenance of 25% diet restriction delayed onset and reduced severity of hip joint osteoarthritis, thus favorably affecting both duration and quality of life. In addition, the data indicated that development of hip joint osteoarthritis was not bimodal in these dogs but occurred as a continuum throughout life.

This report reviews decade two of the lifetime diet restriction study of the dog. Labrador retrievers (n 48) were paired at age 6 weeks by sex and weight within each of seven litters, and assigned randomly within the pair to control-feeding (CF) or 25 % diet restriction (DR). Feeding began at age 8 weeks. The same diet was fed to all dogs; only the quantity differed. Major lifetime observations included 1·8 years longer median lifespan among diet-restricted dogs, with delayed onset of late life diseases, especially osteoarthritis. Long-term DR did not negatively affect skeletal maturation, structure or metabolism. Among all dogs, high static fat mass and declining lean body mass predicted death, most strongly at 1 year prior. Fat mass above 25 % was associated with increasing insulin resistance, which independently predicted lifespan and chronic diseases. Metabolizable energy requirement/lean body mass most accurately explained energy metabolism due to diet restriction; diet-restricted dogs required 17 % less energy to maintain each lean kilogram. Metabonomics-based urine metabolite trajectories reflected DR-related differences, suggesting that signals from gut microbiota may be involved in the DR longevity and health responses. Independent of feeding group, increased hazard of earlier death was associated with lower lymphoproliferative responses to phytohaemagglutinin, concanavalin A, and pokeweed mitogen; lower total lymphocytes, T-cells, CD4 and CD8 cells; lower CD8 percentages and higher B-cell percentages. When diet group was taken into account, PWM responses and cell counts and percentages remained predictive of earlier death.Diet restriction: Dog: Ageing: Longevity During 1987, a diet restriction study of domestic dogs (Canis lupus familiaris) was initiated with a hypothesis that 25 % diet restriction would decrease hip joint laxity and osteoarthritis (OA) in a dog breed that is genetically susceptible to obesity and OA (1) .At 24 months, the experiment was extended for the lifetimes of the dogs. The original experimental design was continued with the added hypothesis that 25 % diet restriction (DR) for lifetime would result in increased longevity and improved overall health of DR dogs, compared to pair-mate control-fed (CF) dogs. The last dog died in mid-2001, at age 14·5 years. The database of physiological observations from this study is large and diverse, and earlier communications have occurred over an elapsed time of about 15 years. This report reviews the key findings of the second decade of this work and presents our view of the most important inter-species comparative observations. Overview of general methods Study designLabrador retrievers (n 48) were paired at age 6 weeks by sex and body weight within each of seven litters, and then were assigned randomly within the pair to CF or 25 % DR. Beginning at age 8 weeks, each CF dog was given the dry, extruded diet ad libitum, and each DR pair-mate was given 75 % of the amount of food that its CF pair-mate had consumed the previous day. Each feeding g...

D uring the 20th century, a large body of research evolved toward understanding aging and how aging can be influenced in individuals and in populations. A considerable portion of this effort has focused on elucidating roles of nutrition, including nutrient requirements during senescence, complications and treatment of chronic diseases, and preventive strategies to delay chronic disease and death. The association among energy intake, energy utilization, and aging is particularly interesting in this respect. The most wellknown intervention is long-term restricted food intake, which has a favorable influence on the life span of species as diverse as nematodes, spiders, rotifers, water fleas, fruit flies, fish, hamsters, mice, rats, and dogs. 1-3 Food restriction also modulates physiologic processes that may influence the expression of diseases that develop later in life. Results of studies 1-6 of rodents, dogs, and primates indicate that food restriction delays age-related death from species-, breed-, and strain-specific causes. Evaluation of lifetime food restriction in a population of dogs offered the opportunity to assess characteristics and predictive aspects of intrinsic (nonenvironmental, arising from inside the body 7,8) death in a large species that has a mean life span that lies intermediately between lower mammals, which have been studied extensively by use of food restriction models, and primates that presently are the subject of similar studies. 1,4-6 The purpose of the data reported here is to describe effects of lifetime food restriction on causes of death and associations among body composition and time of death in dogs. Overall life span data from this study have been previously reported. 2 Materials and Methods Dogs and housing-Forty-eight Labrador Retrievers from 7 litters were allocated to a paired-feeding study design. 9-11 Dogs were paired at 6 weeks of age by sex and body weight within litter and randomly allocated to either a control-fed or restrictedfed group. Dogs were housed in 2 X 19-m indoor-outdoor kennel runs with concrete floors. Free access to outdoors was available, and the activity level of the dogs was not restricted. All dogs were housed in the same environmental conditions for life, with no difference between feeding groups. Kennel assignment was maintained by original pairing, with either 2 (1 pair) or 4 (2 pairs) dogs/kennel. The study was approved by the supervising institutional animal care and use committee. Diets and feeding regimens-Control-fed and restrictedfed dogs ate the same nutritionally complete and balanced noncommercial formula; only the quantity of diet provided was different between feeding groups. 9-11 Beginning at 8 weeks of age, each restricted-fed pair mate was fed a quantity equal to 75% of the amount of food that was consumed on the previous day by the respective control-fed pair mate. When the dogs were 3.25 years old, 2 adjustments were incorporated into the feeding protocol. All dogs were switched from a growth formula containing 27% protein to an adult...