This study evaluated the effect of supplementary antioxidants and whey protein on immune-system challenges in 4 groups of 7-week-old puppies. For 6 weeks pups were fed a control diet or 1 of 3 test foods-control food plus antioxidants, control food plus antioxidants plus 1% whey protein, or a grocery store brand. At weeks 2 and 4, a standard vaccination with canine parvovirus (CPV) and canine distemper (CDV) was given. Blood samples were obtained weekly. Titers were measured weekly from day 14 to day 42. Blood was collected on days 1 and 34 to test for lymphocyte proliferation and lymphocyte subset analysis. Antibody titers to CDV increased in all the groups after vaccination but were significantly higher in pups receiving both types of the antioxidant foods compared with the other groups. Titers in the supplemented groups were also significantly higher compared with the control group after the booster vaccination and tended to be higher than in the grocery-store-brand group. The response to the CPV vaccine at weeks 2 and 3 was significantly higher for pups receiving control food plus antioxidant than in either those consuming the control food or control food plus antioxidants plus 1% whey protein. The control-food-plus-antioxidant group also had more CD4+ memory cells than did the control-food group. CD8 memory cells were increased, albeit insignificantly, in all groups. The antioxidants used in the study were vitamin E (500 IU/kg dry matter [DM]), vitamin C (970 mg/kg DM), β-carotene (0.4 mg/kg DM), and selenium (0.8 mg/kg DM).

Commentary: The role of antioxidants in nutrition is twofold: first, they protect the diet itself from oxidative destruction during storage and, second, they confer protection against oxidative processes in the animal's body. Not all antioxidants function by the same mechanisms; hence the possibility exists that combinations of antioxidants may provide synergistic benefits. At the same time, some combinations may be less than ideal. Progress in this area has been made but is often slowed by not knowing the best overall measurements of protection for assessing antioxidant benefits in the animal. A diet containing a specific blend of tocopherols (including vitamin E), β-carotene, and ascorbic acid was evaluated in a number of appropriate tests and compared to a diet with these components plus whey protein and to a grocery brand. Results suggested that an increase in the recommended amount of vitamin E may be beneficial when this combination is used. Blends of antioxidants will likely continue to be used in complete and balanced companion animal foods.

The role of supplementary dietary antioxidants on immune response in puppies. Koo C, Cunnick J, Griesen K, et al. VET THER 6:43-56, 2005.