Effect of Withania somnifera (L. Dunal) root as a feed additive on immunological parameters and disease resistance to Aeromonas hydrophila in Labeo rohita (Hamilton) fingerlings

The present study evaluated the efficacy of dietary doses of Withania somnifera (Ashwagandha) root powder on immunological parameters and disease resistance against the bacterial pathogen Aeromonas hydrophila infections in Indian major carp, Labeo rohita fingerlings. Fishes were fed with dry diet containing 0 g kg−1 (control), 1 g kg−1 (T1), 2 g kg−1 (T2) and 3 g kg−1 (T3) W. somnifera root powder for 42 days. Immunological (NBT level, Phagocytic activity, total immunoglobulin and lysozyme activity) parameters of fishes were examined at 0 days,14 days, 28 days and 42 days of feeding. Fishes were challenged with A. hydrophila 42 days post feeding and mortalities (%) were recorded over 14 days post-infection. The results demonstrate that fishes fed with W. somnifera root showed enhanced NBT level, Phagocytic activity, total Immunoglobulin level and lysozyme activity (p < 0.05) compared with the control group. The survivability was higher in experimental diets than the control group. Dietary W. somnifera at the level of 2 g kg−1 showed significantly (P < 0.05) higher protection (RPS 42.85 ± 0.65%) against A. hydrophila infection than control. The results suggest that the W. somnifera root powder have a stimulatory effect on immunological parameters and increases disease resistance in L. rohita fingerlings against A. hydrophila infection.