Introduction
With regard to side effects of antibiotic therapy, there is an increasing attention to herbal plants as a substitute for synthetic medications. The oregano plant (Origanum vulgare), because of its antioxidant, antimicrobial and anti-inflammatory features, has been surveyed in different fish species and proved to have significant effects in improving immune system and accelerating growth rate. In this study, the effect of oregano essential oil is examined in sterlet sturgeon for the first time.
Materials and Methods
Diets were fortified with five levels of Oregano essential oil (0, 2, 5, 8, 10 g/kg). Two hundred and twenty five sterlet sturgeons (25±1 g) were divided into five treatments (in 3 replicates) and fed with the diets for twelve weeks. At the end of feeding trial, the activity of liver enzymes (SOD, CAT, MDA) was assessed. After a fifteen-day-challenge, the cumulative mortality rate with Aeromonas hydrophila was recorded.
Results
The results of the trial revealed that oregano essential oil increased the immunity levels of sterlet sturgeon. The levels of CAT and SOD in fish fed with 10 g/kg oregano significantly increased compared with other treatments (p<0.05). Also, the 2 and 5 g/kg groups did not show a significant difference compared with the control group (p>0.05).
After challenging with Aeromonas hydrophila, cumulative mortality decreased significantly as the dose increased (p<0.05). The results of the experiment showed positive effects of oregano essential oil in improving the antioxidant defense capability and increasing survival rate of sterlet sturgeon challenged with bacterial infection.