Abstract
Study on disease resistance and antiviral property was conducted in laboratory by feeding juveniles with a supplementary pellet feed containing alcohol extract of B.diffusa at 2, 4, 6, 8 and 10 ml/kg. On 21st day of rearing, juveniles were challenged by feeding WSSV infected (PCR +ve) shrimp carcass. Juveniles received a diet containing B.diffusa at 8 and 10 ml/kg showed significantly (P<0.01) high survival than other doses. After standardization, the optimum dosage (8 and 10 ppm) obtained from antiviral study was incorporated in a commercially available supplementary feed and fed to juveniles of tiger prawn for a period of 120 days in brackish water earthen ponds. An extract free diet was served as control. Average growth, feed conversion efficiency, apparent nutrient digestibility, total haemocyte count (THC), digestive enzymes activity and RNA/DNA ratio were high in B.diffusa extract fed shrimp compared to control. B.diffusa extract contains bioactive compounds which could induce growth by enhancing voluntary feed intake, nutrient digestion and immunomodulatory property of shrimp.