Supplementation of combined mannan oligosaccharide and β-glucan immunostimulants improves immunological responses and enhances resistance of Pacific Whiteleg Shrimp, Penaeus vannamei, against Vibrio parahaemolyticus infection

A feeding trial was conducted to evaluate the combined effects of mannan oligosaccharide ( MOS) + β-glucan (BZT® PRE-GE) supplementation administered at different frequencies on the immune responses and resistance of Penaeus vannamei against Vibrio parahaemolyticus, the causative agent of Early Mortality Syndrome (EMS) disease. Four experimental treatments were run with shrimps fed with a control basal diet (TCo), fed daily with diet containing 0.2 % MOS+ β-glucan (Td), fed every 3 days with diet containing 0.2 % MOS+ β-glucan (Td3) and fed every 7 days (Td7) with diet containing 0.2 % MOS+ β-glucan. Following the 30-day feeding trial, shrimp immunological responses were quantified. Infection challenge test was also conducted to evaluate the influence of the treatments on the resistance of P. vannamei against V. parahaemolyticus infection. Results indicate that the immunostimulant application frequency did not affect shrimp survival and overall growth performance. Immunostimulant application every 3 days was found optimum to enhance the immunological responses including total hemocyte count, prophenol oxidase and serum antibacterial activities. Moreover, significant improvement in survival following the infection challenge with V. parahaemolyticus was observed in treatment fed with the immunostimulant every 3 days. Overall these findings suggest that 0.2 % MOS+ β-glucan supplementation applied every 3 days could enhance the immune responses and improve the resistance of P. vannamei against Vibrio parahaemolyticus infection. Administration of 0.2 % MOS+ β-glucan once every 3 days could be a practical immunoprophylactic strategy to manage and prevent outbreaks of mass mortalities caused by V. parahaemolyticus infection in P. vannamei farming.