Alginic acid as immunostimulant: effects of dose and frequency on growth performance, immune responses, and white spot syndrome virus resistance in tiger shrimp Penaeus monodon (Fabricius, 1798)

Effects of dose and frequency on growth performance, immune responses, and resistance to white spot syndrome virus (WSSV) of Penaeus monodon fed diets containing alginic acid (ERGOSAN®; Schering-Plough Aquaculture, UK) were investigated. Shrimp were fed alginic acid-incorporated diets at different concentrations (0, 500, 1000, 2000, and 4000 mg kg−1) for 35 days and challenged with WSSV by immersion. Results indicate that dietary inclusion of alginic acid 1000 mg kg−1 enhances resistance of the shrimp against WSSV infection. This dose was further tested given at varying feeding frequencies (daily, once every 3 days, once every 7 days, and once every 10 days) to enhance disease resistance. Shrimp fed 1000 mg kg−1 alginic acid once every 3 days resulted to better growth and survival against WSSV infection. This enhanced resistance against infection is attributed to the enhancement of immunological responses including total hemocyte count (THC), superoxide anion (O2−) production, and phenoloxidase (PO) activity. The present study elucidates the importance of optimum dosage and frequency of alginic acid as immunostimulant to elicit an optimum immunoprotective effects against WSSV infection in juvenile P. monodon.