This study was conducted to test the hypothesis that dietary L-arginine supplementation enhances immunity in early-weaned piglets. Seventy piglets weaned at 7 days of age were assigned to 5 groups (14 pigs/group), representing supplementation of 0.0％, 0.2％, 0.4％, 0.6％ and 0.8％ L-arginine to a milk-based formula. On Day 7 after initiation of treatment, spleen weight in piglets supplemented with 0.2％ and 0.8％ arginine was heavier and thymus size was larger in piglets supplemented with 0.6％ arginine, whereas serum concentration of immunoglobulin (Ig) M was higher but that of IL-8 was lower in piglets supplemented with 0.6％ and 0.8％ arginine, compared with the control group. Dietary supplementation with 0.8％ arginine increased the numbers of white blood cells and granulocytes, and gene expression of interleukin (IL)-8 in spleen. On Day 14, compared with control piglets, granulocyte numbers were greater but lymphocyte numbers were lower in piglets supplemented with 0.2％ and 0.4％ arginine, whereas splenic expression of IL-8 and tumor necrosis factor-α genes was increased in piglets supplemented with 0.8％ arginine. Additionally, IgG and IgM concentrations in serum and growth performance were greater in piglets supplemented with 0.4-0.8％ arginine, compared with unsupplemented piglets. Collectively, dietary supplementation with 0.4-0.8％ L-arginine for two weeks enhances both cellular and humoral immunity in piglets by modulating the production of leukocytes, cytokines and antibodies. These results indicate that increasing L-arginine provision is beneficial for optimal immune responses in young pigs and also have important implications for designing the next generation of improved formula for human infants.
Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of SubtropicalAgricult Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agricul Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of SubtropicalAgricult Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of SubtropicalAgricult Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of SubtropicalAgricult Key Laboratory of Food Science of The Ministry of Education, Department of Food Science andEngineeri Department of Animal Nutrition, Ajinomoto Inc., Tokyo, 104-8135, Japan Key Laboratory for Agro-ecological Processes in Subtropical Region, Institute of SubtropicalAgricult