Antioxidant Status of Pair-Fed Labrador Retrievers Is Affected by Diet Restriction and Aging

Twenty-four sibling pairs of 8-wk-old Labrador Retrievers were assigned to an experiment to determine the effects of diet restriction (75% of control-fed pair mate) on the quality and span of canine life and to identify biological markers of aging in dogs. The antioxidant status of these dogs was monitored by annual assays for serum retinol (RT), retinyl palmitate (RP), total vitamin A (VA), vitamin E (VE), selenium (Se), copper (Cu), and ceruloplasmin (Cp), plasma ascorbic acid (AA), uric acid (UA), and total peroxyl-radical trapping activity (TRAP), and whole-blood glutathione peroxidase (Gpx). Data in this report are for the 6-y period of the experiment when the dogs were between 5 and 10 y of age. Diet restriction reduced RT, VE, Cu, and Cp. Aging was associated with decreased RP, VA, VE, Se, and Cu and with increased RT, Cp, and Gpx. Female dogs had lower RP, VA, Cu, and Cp than male dogs. Litter effects were observed for VE, Cu, UA, and Gpx. Treatment effects on serum RT and Cu suggest that these variables are not as regulated homeostatically by hepatic storage as in most other species. Although the antioxidant profiles did not elucidate how diet restriction contributes to longevity, they have the potential to enhance our understanding of canine clinical nutrition and to have practical applications in formulating canine diets.