Abstract
Studies were conducted to examine the therapeutic effects of selected medicinal plants and low cost chemotherapeutics on the health management of silver barb (Barbodes gonionotus). The medicinal plants were applied by mixing with feed whereas chemotherapeutics were applied through immersion method (dip treatment). A total of 43 medicinal plants were examined to know the inhibitory effect on the growth of fungal and bacterial fish pathogen under in vitro condition. The leaf of pepperwort (Polygonum hydropiper), turpeth root (Opaculina turpethum), mast tree (Polyalthia longifolia), Justicia gendarussa, rhizome of arrowroot (Curcuma zedoaria) and turmeric (Curcuma longa) and seed of black cumin (Nigella sativa) were highly effective in inhibiting the growth of fungal pathogen. Again leaf of crown flower (Calotropis gigantea), Indian sorrel (Oxalis corniculata), Aphanamixis polystachys, guava (Psidum guajava), tamarind (Tamarindus indicus) and bulb of garlic (Allium sativum) were highly effective in inhibiting the growth of bacterial pathogen. But in feeding efficacy test with silver barb, it was found that seed of black cumin, rhizome of arrowroot, leaf of Indian sorrel and guava were easily taken by silver barb when they were mixed 10% in crushed form with normal feed. In pond trial, growth and survival of fish were found to be relatively higher where 10% medicinal plants were used in the feed. In the challenge test, they were found to be less susceptible to infection by the pathogens (aquarium test). The seed of black cumin performed better resistance against fungal infection (Saprolegnia sp. Aphanomyces invadans and Achlya sp.) and Indian sorrel performed better in the case of bacterial infection (Aeromonas hydrophila, Pseudomonas fluorescens and Edwardsiella tarda). A total of 5 chemicals were used in dip test for 5 to 10 minutes to resist bacterial infection in silver barb. These were alum (1g/l), salt and lime mixture (1g + 1g/l), doxycycline (50 mg/l) and oxytetracycline (100 mg/l). Salt and lime mixture performed better than alum alone in case of bacterial infection. There was significant difference among the chemotherapeutics test at 5% levels. But, no infection was found in the treatment of doxycycline and 3.33 to 10% infection was observed in the treatment of oxytetracycline. In challenge test with fungal pathogen, alum performed better than salt and lime mixture. Again, higher recovery was found by the treatment of alum of the same dose in the artificially infected silver barb. Moreover, it was found that the use of alum (1 mg/l) stopped the spread of fungal infection in the dumping pond. No histological alteration was observed in skin, muscle, gill, liver and kidney of silver barb, when it was exposed for 120 hrs. at 0.5 g alum/l. It was concluded that health management of cultured fishes like silver barb could be performed by using medicinal plants like black cumin and Indian sorrel through feeding. Guava and arrowroot might also be good additives to prevent bacterial and fungal disease. Alum might be used in controlling fungal diseases of fish. Doxycycline and oxytetracycline could be effective against bacterial disease of cultured fish.