Effect of dietary Syzygium cumini leaf powder on growth and non-specific immunity of Litopenaeus vannamei (Boone 1931) and defense against virulent strain of Vibrio parahaemolyticus

The study was aimed to assess the growth and immunomodulatory potential of Syzygium cumini leaf powder against virulent strain of Vibrio parahaemolyticus on the juveniles of Litopenaeus vannamei. Two diets such as control diet (without immunostimulant) and immunostimulant diet (containing 1% S. cumini leaf powder) were prepared. The juveniles were distributed in four treatments namely; daily feeding of control diet (CD), daily feeding of immunostimulant diet (ID), alternate day feeding of control and immunostimulant diet (CD/ID) and two days control diet and one day immunostimulant diet (2CD/ID) feeding. After feeding trial, shrimps from each treatment group were challenged with 0.1 mL of virulent strain of V. parahaemolyticus suspension at a concentration of 107 CFU mL−1. The post-challenge sampling was performed after 5 days of injection. The haemolymph prophenol oxidase, superoxide dismutase, catalase and respiratory burst activity of different treatments were significantly different (P < 0.05) in both pre- and post-challenge conditions. The haemolymph total protein, globulin, lysozyme and phagocytic activities of L. vannamei fed with Syzygium cumini leaf powder improved than the control group in pre- as well as post-challenge phase. The survival rate of shrimps fed with immunostimulant diet was significantly (P < 0.05) higher as compared to control group. Therefore, Syzygium cumini leaf powder added diet protects the host effectively against virulent strains of V. parahaemolyticus through both continuous and alternate day feeding.