Dietary brown macroalga Ascophyllum nodosum improves growth, antioxidant, immunity responses, and resistance to Vibrio harveyi infection in white-leg shrimp, Penaeus vannamei

Abstract This study investigated the beneficial effects of dietary supplementation with brown macroalga, Ascophyllum nodosum meal (ANM) on growth, digestive enzymes, antioxidant defenses, immune functions, and resistance of white-leg shrimp, Penaeus vannamei to Vibrio harveyi infection. Animals were divided into six triplicated groups and fed with 0 (control), 5, 10, 20, 30, and 40 g ANM/kg feed for 10 weeks. Afterwards, animals were experimentally infected with V. harveyi , and their mortality was observed over the next 10 days. The in vitro investigation evoked that the ethanolic extract of A. nodosum meal exhibited antioxidant and antibacterial activity against V. harveyi . Furthermore, the inclusion of ANM in diets notably improved the feed efficiency and productivity indices of P. vannamei , and the optimum outcomes were observed at 30–40 g ANM/kg feed. These enhancements could be associated with significant enhancements in proteases, lipase, and α-amylase activities in intestinal tissues due to dietary ANM. Superoxide dismutase (SOD) and catalase (CAT) activity, along with serum total protein, lysozyme activity, respiratory burst activity, and phagocytic activity, were maximized in shrimp fed with 30–40 g ANM/kg feed. Compared to the control group, malondialdehyde (MDA) concentrations revealed significant declines in shrimps that received ANM-enriched diets, particularly 30–40 g/kg feed. The mRNA expression of cat , cMn-sod , a2m , and pen3a genes was upregulated as ANM levels in diets increased. After the challenge with V. harveyi , the highest shrimp mortality was found in the control group (83.3%); meanwhile, shrimps fed on 30–40 g ANM/kg diet exhibited the lowest cumulative mortality (36.7–43.3%) with relative percent survival (RPS) of 48.1% and 55.6%, respectively. No marked differences were detected in animals’ mortality or RPS between both of treatments. Based on the above-mentioned findings, this research recommends adding 30 g ANM/kg feed to shrimp diets to enhance their growth, antioxidant, and immune performances as well as prompt its resistance to possible V. harveyi infection in white-leg shrimp.