Dietary arginine levels alter markers of arginine utilization in peripheral blood mononuclear cells and thymocytes in young broiler chicks

Arginine is an essential amino acid in Aves and is also an important substrate for the immune system. Dietary Arg in avian diets must be sufficient to not only support growth but also immunity. To better understand Arg needs for immunity, 2 experiments examined markers of Arg use by the immune system in growing broiler chicks. Broiler hatchlings were fed diets containing adequate (1.2%) or high (1.35%) dietary Arg for 21 d. On d 7, the Arg importer cationic amino acid transporter-1 mRNA abundance in peripheral blood mononuclear cells was 2-fold greater in chicks fed 1.35% Arg than in chicks fed 1.2% Arg (P < 0.05). On d 14, chicks fed the diet containing 1.2% Arg had 2.5-fold greater mRNA abundance of the y(+)L type amino acid transporter-2 exporter compared with chicks fed 1.35% Arg (P < 0.05). In experiment 2, broiler hatchlings were fed diets containing low (1.1%), high (1.3%), or excess (1.5%) dietary Arg for 17 d. The percentage of peripheral blood B cells at a given age tended (P = 0.06) to be affected by the dietary Arg level. On d 14, but not on d 10 or 17, the percentage of monocytes from chicks fed 1.5% Arg was higher than from those fed 1.1 and 1.3% Arg (P < 0.05). These studies indicate that the dietary Arg levels in excess of 1.2% increase the mRNA abundance of markers for Arg use by immune cells undergoing development (thymocytes) and at maintenance (peripheral blood mononuclear cells) and also increase the percentage of monocytes within peripheral blood. Understanding Arg use by the immune system will provide a better understanding of how to formulate immunosupportive diets to promote animal health.