Effect of butanolic extracts from terrestrial herbs and seaweeds on the survival, growth and pathogen (Vibrio parahaemolyticus) load on shrimp Penaeus indicus juveniles

Emergence of microbial disease in aquaculture industries implies serious financial lose. Usage of commercial antibiotics for disease treatment produces undesirable side effects. Certain ayurvedic herbal compounds are having potent effect on growth and survival as well as antimicrobial properties of aquatic organisms. In this study, six types of antimicrobial compounds were extracted using n-butanol from terrestrial plants such as Ricinus communis (T1), Phyllanthus niruri (T2), Leucus aspera (T3), Manihot esculenta (T4) and sea weeds Ulva lactuca (T5) and Sargassum wightii (T6). The yield of extractable matter was between 10.20% and 17.50%. The antimicrobial activity of these extracts was tested against shrimp pathogen Vibrio parahaemolyticus by giving due consideration to zone of inhibition. Powder form of these extracts was bioencapsulated in Artemia and fed to Peneaus indicus juveniles reared in individual tanks inoculated with shrimp pathogen V. parahaemolyticus at the rate of 10⁷CFU ml-1. P. indicus juveniles reared in V. parahaemolyticus uninoculated water and fed with unenriched Artemia (C1) exhibited maximum survival (86.10%), specific growth rate (SGR, 2.87%) and less bacterial load (0.43 and 0.52x10³ CFU g-1 in muscle and hepatopancreas tissues). The shrimps reared in V. parahaemolyticus inoculated medium and fed with unenriched Artemia (C2) showed lowest survival (24.44%), specific growth rate (1.11%) and more bacterial load (3.71 and 3.86x10⁵ CFU g-1 in muscle and hepatopancreas tissues). The shrimps fed with herbal and seaweed diets-enriched Artemia (T1-T6) boosted the survival (43.32-58.88%), specific growth rate (1.46-2.15%) and lowered V. parahaemolyticus load (1.36-2.03 and 1.47-2.16x10⁵ CFU g-1 in muscle and hepatopancreas tissues, respectively) in the culture system. Among the herbal diets screened, R. communis (T1) gave better results than the other products. The findings of the present study would be highly useful to produce quality, disease-free shrimps with high production.