Immune responses to methanolic extract of black cumin (Nigella sativa) in rainbow trout (Oncorhynchus mykiss)

The immune stimulating effects of the methanolic extract of black cumin (Nigella sativa) in rainbow trout (Oncorhynchus mykiss) was evaluated. Variable concentrations of black cumin methanolic extract [0 (Control), 0.1 and 0.5 g kg(-1) of feed] were individually added to the basal diet and rainbow trout was fed for 30 days to assess the innate immune responses and growth performance. Feed conversion ratio significantly decreased in the group fed with 0.5 g kg(-1) black cumin extract. Respiratory burst activity was observed to be the highest in the 0.5 g kg(-1) black cumin extract fed group. Lysozyme and myelo-peroxidase activities were significantly increased in fish of experimental groups compared to control (P < 0.05). TGF-beta gene expression increased in black cumin 0.5 g kg(-1) treated group. IL-1 beta and TGF-beta gene expressions decreased in black cumin 0.1 g kg(-1) administered group. Expression of IL-12 gene diminished in both the experimental groups. There was no significant difference in survival rates between black cumin extract treated fish groups and control (P > 0.05) after challenged with Aeromonas hydrophila. The results indicate that the methanolic extract of black cumin is a stimulator of some innate humoral immune responses, but it is ineffective for cytokine-related gene trancriptions in rainbow trout. (C) 2017 Elsevier Ltd. All rights reserved.