Effects of Bidens alba and Plectranthus amboinicus dietary supplements on nonspecific immune responses, growth, and resistance to Vibrio alginolyticus in white leg shrimp (Penaeus vannamei)

Abstract

Bidens alba and Plectranthus amboinicus are common medicinal plants. This study investigated the effects of a diet containing B. alba extract (BAE) and P. amboinicus extract (PAE) on the immune responses, growth, and their resistance to Vibrio alginolyticus in white leg shrimp (Penaeus vannamei). An in vitro experiment revealed that the BAE and PAE are nontoxic to white leg shrimp haemocytes, and the extracts increased phagocytic activity, superoxide anion (O-2(-)) production, and phenoloxidase (PO) activity. In in vivo trials, shrimp were fed diets containing 10, 20, or 40 g of BAE (B1, B2 and B4) or PAE (P1, P2 and P4 group) per kg of regular feed for 28 days, and immune parameters were measured. All BAE and PAE groups exhibited enhanced nonspecific immune responses including increased total haemocyte count, phagocytic activity, O-2(-) production rate, and PO activity. Shrimp fed the BAE or PAE diet for 7 days exhibited increased expression of Lysozyme (Lyz), Penaeidin 2 (Pen2), Penaeidin 3 (Pen3), and Penaeidin 4 (Pen4). After a V. alginolyticus challenge, the treated shrimp exhibited higher survival rates than exhibited by those fed the control diet. The growth performance results of 56 feeding trials revealed that shrimp fed BAE or PAE at 20 g/kg (B2 or P2 group) gained significantly more weight and has a significantly higher specific growth rate than did those on the control diet. Thus, these results suggest that administration of 20 g of BAE or PAE per kilogram of feed can enhance immunity, growth, and resistance to V. alginolyticus in white leg shrimp.