Astragalus Polysaccharides Enhance Cellular Immune Response and Disease Resistance in Yellow Catfish

Abstract

We studied the effects of dietary astragalus polysaccharides on the cellular immune response of yellow catfish (Pelteobagrus fulvidraco). 540 Yellow catfish were fed different levels of astragalus polysaccharides (0, 300, 600, 900, 1200, or 1500 mg/kg diet) for eight weeks. Non-specific immune responses were measured at the end of the experimental feeding. We then challenged control and treated fish with an intraperitoneal injection of Aeromonas hydrophila and recorded mortality for seven days. Groups treated with 1200 mg/kg displayed a significant increase in oxygen respiratory burst (oxidative burst) activity of head kidney macrophages (p<0.05), along with significant increases in nitrogen respiratory burst activity (p<0.01) and leukocyte proliferation (p<0.05). The 1500 mg/kg group also displayed significant increases in nitrogen respiratory burst activity (p<0.01) and leukocyte proliferation (p<0.05). The lowest mortality was obtained in the 1200 and 1500 mg/kg groups. These data indicate that dietary astragalus polysaccharides may effectively enhance cellular immune responses and disease resistance, and reduce mortality, in yellow catfish against A. hydrophila infection.