M icrocystis aeruginosa ( K ütz) incorporated diets increase immunity and survival of I ndian major carp L abeo rohita ( H am.) against A eromonas hydrophila infection

The aim of this study was to evaluate dietary dosages of M icrocystis on the immune response and disease resistance against infections due to the opportunistic pathogen A eromonas hydrophila in L abeo rohita fingerlings. L abeo rohita fingerlings were fed diet containing 0 ( C ontrol), 0.5, 1.0 and 5 g M icrocystis powder kg −1 dry diet for 90 days. Three replicate groups of fish averaging 20 ± 2 g were fed for 3 months daily. At 30 days interval, samples were assayed for different biochemical [serum total protein, albumin, globulin, albumin:globulin (A:G) ratio] and immunological (superoxide anion production, lysozyme and serum bactericidal activity) parameters. The results demonstrate that fish fed M icrocystis showed increased levels of lysozyme, serum bactericidal activity, serum protein and albumin ( P  ≤ 0.05) as compared with the control group. After 90 days, fish were challenged with A . hydrophila and mortality (%) was recorded up to day 10 postchallenge. The group fed 1.0 g M icrocystis  kg −1 dry diet showed the highest percentage survival (72%). These results indicate that M icrocystis aeruginosa stimulates the immunity and makes L . rohita more resistant to infection by A . hydrophila when fed in dried form in feed.