Effects of the apple mangrove (Sonneratia caseolaris) on antimicrobial, immunostimulatory and histological responses in black tiger shrimp postlarvae fed at varying feeding frequency

The study aimed to evaluate extracts of the apple mangrove (Sonneratia caseolaris) as agentof prophylactic/therapeutant for the culture of Penaeus monodon. General types of compounds detectedin the leaf and twig extracts were glycosides, steroids, triterpenes, sterols and flavonoids as determinedby Thin Layer Chromatography (TLC). Based on the mean clear zone of inhibition, twig extract exhibitedhigher antibacterial activity than did the leaf extract. Furthermore, the methanolic extract of the twiggave the highest antibacterial activity and was thus employed for further tests. It was incorporated inthe basal diet (commercially available shrimp starter feed) and was tested at three feeding frequencies(twice, three and four times daily) for its effects on the immune responses against a control treatment(pure basal diet) fed three times daily. There were no significant differences in respiratory burstactivities between treatments but shrimps fed medicated diets exhibited considerably higher values thandid the control group of shrimps. Phagocytic and phenoloxidase activities were significantly higher inshrimps fed medicated diets at all feeding frequencies than did those fed the control diet; activities werenot significantly different between those fed medicated diets. Bacterial survival index was significantlyhigher in shrimps fed the control diet than did those fed medicated diets; indices of shrimps fedmedicated diets were not significantly different. There were no signs of toxicity or any adversehistological changes in shrimps fed medicated diets at 1000 μg mL-1 apple mangrove extractconcentration.