Mitigating effects of dietary supplementation with Panax ginseng essential oil on atrazine-induced toxicity in Nile tilapia (Oreocromis niloticus)

Dietary use of essential oils in aquaculture has been receiving increasing attention as an alternative strategy for improving resistance to biological and non-biological stresses (e.g. pathogens and environmental toxicants), growth performance and overall welfare of farmed fish [1]. In the present study, we tested dietary supplementation with Panax ginseng essential oil (GEO) for its efficacy at mitigating the adverse effects that the water-soluble herbicide atrazine (ATZ) is able to induce in Nile tilapia (Oreochromis niloticus) as a consequence of contamination of aquatic ecosystems [2]. To this aim, 180 fish were allocated into 6 triplicate experimental groups, where one group (control) was reared in clean water and fed a commercial basal diet, two groups (GEO1 and GEO2) were fed the basal diet supplemented with two different levels of GEO (1.0 and 2.0 mL/kg diet), one group (ATZ) was intoxicated with 1/5 of ATZ 96-h lethal concentration 50 (1.39 mg/L), and the remaining two groups (GEO1+ATZ and GEO2+ATZ) were fed the GEO-supplemented diets and concurrently exposed to 1.39 mg ATZ/L. After a 60-day experimental period, inter-group differences were analysed by one-way ANOVA, followed by Tukey's multiple comparison test. The study was approved by the Institutional Ethics Committee of the Faculty of Veterinary Medicine of Zagazig University (Egypt) and was conducted in accordance with the Local Experimental Animal Care Committee guidelines. Consistently with previous studies using herbal ginseng [3], both levels of dietary GEO supplementation of healthy Nile tilapia exerted significantly positive influence (P<0.001) on fish growth and feed utilization parameters, as well as on fish immunity (increased leukocyte counts and IgM levels) and hepatic antioxidant defense systems. Exposure to sub-lethal ATZ concentration was confirmed to significantly reduce (P<0.001) fish survivability, growth and feed utilization [4], as well as to induce significant negative changes (P<0.001) in intestinal digestive enzyme activity (decreased lipase activity), hematological indices (decreased hemoglobin, packed cell volume, erythrocytes and leukocytes), blood biochemical variables (decreased total proteins, albumin, globulins and IgM; increased total cholesterol, triglycerides and cortisol), hepatic oxidative/antioxidant indices (decreased superoxide dismutase and catalase enzyme activity and mRNA expression levels, decreased glutathione level and increased malondialdehyde content), hepatic reactivity indices (upregulated mRNA expression of the stress- and apoptosis-related genes Hsp70, caspase 3 and p53) and hepatic histomorphology (lesions referring to early hepatoma). Of interest, dietary GEO supplementation in GEO1+ATZ and GEO2+ATZ groups significantly attenuated (P<0.05) most of the aforementioned negative effects of ATZ, though for some parameters still not reaching the control values even at the higher supplementation level. Taken together, the findings of the present study provide further and partly new evidence that dietary GEO supplementation may be useful not only to provide general support to productive performance and health/welfare status of Nile tilapia, but also for mitigating the impact of sub-lethal ATZ toxicity in this fish species.