The effect of Marjoram (Origanum vulgare L.) and St John's Wort (Hypericum perforatum) hydro-alcoholic extracts on growth, immunity, digestive and antioxidative enzymes activity of rainbow trout (Oncorhynchus mykiss) under the commercial farming condition

The present study was conducted to investigate the effects of hydroalcoholic extracts of Marjoram and St John's Wort on growth, immune indices and activity of digestive and antioxidative enzymes in rainbow trout. Treatments included the control group, 3% Marjoram, 3% St John's Wort and the combination of both extracts (1.5%). The condition factor of fish received 3% Marjoram extract was significantly different from other experimental groups. The highest final weight belonged to diet supplemented with 3% Marjoram extract (P<0.05). SGR showed an 8.3% increase in 3% Marjoram extract in comparison to the control group and FCR showed a 2.34% decrease in the same treatment as well. The immune indices (immunoglobulin, complement sub-path activity,and serum lysozyme) and antioxidant enzymes activity (glutathione peroxidase, catalase, and superoxide dismutase) of different treatments were affected by the experimental diets (P <0.05). The lowest and the highest values belonged to the control group and 3% Marjoram extract, respectively (P <0.05). There were significant differences in digestive enzymes activity (amylase, lipase, and protease) (P<0.05) between the 3% Marjoram extract treatment in comparison to the control group regarding. In conclusion, the results showed that dietary supplementation of the hydroalcoholic extract of Marjoram significantly improved the innate immune indices and digestive and antioxidant enzymes activity of rainbow trout under the commercial farming conditions.