Enhancement of Immunological Responses by Dietary Arthrospira platensis and Possibility of Field Applications as Alternative to Antibiotics in Broiler Chicken

Arthrospira platensis is one of the candidates expected to replace antibiotics by its immunostimulatory effects in broiler industry, but the evaluation aimed at field applications is not enough. Here, we measured general immunological indicators such as specific antibody responses against sheep red blood cell and Brucella abortus, serum immunoglobulin concentrations and monocyte phagocytic capacity of broiler chickens, which assigned to four dietary treatment groups: A. platensis at 0, 0.01, 0.1 and 1% was added to their normal feed. Then, the 0.01 to 1% groups were compared to the 0% group. In specific antibody responses, the 0.1% group maintained a higher antibody titer against sheep red blood cells, while the 0.01% group did against Brucella abortus after the secondary response. Regarding serum immunoglobulin concentrations, IgG levels of the 0.1 and 1% groups were significantly higher, while IgA levels showed no significant differences. In the phagocytosis assay, each supplemented group showed an increase of the phagocytic capacity of blood monocytes. In several tests, the 1% group presented heteroscedasticity, i.e., some individuals showed high responses, while others presented poor responses. These observations indicate that dietary A. platensis enhances not systemic but some particular immune responses in broiler chickens and a high level of supplementation may inhibit this effect. Therefore, a dietary supplementation of 0.1% of A. platensis with some immunomodulatory substances that enhance mucosal immunity is suitable for upregulating the systemic immune response in broiler chickens.