The effects of thyme oil extract to reduce toxic effects of Nanosilver on growth factors and serum biochemical in goldfish (Carassius auratus gibelio)

In this study, we divided 300 goldfish (average weight: 12.30 ± 2.11 g) into 4 groups. Fish were fed diets that contained 4 levels of thyme extract: 0 (control), 200, 400 and 800 mg/kg (Thyame, LN23IN, France) for a period of 2 weeks. At the end of 2 weeks, each group of the mentioned treatments was divided into 2 groups: nanosilver-exposed group and control. In the aquarium of the nanosilver-exposed group, we prepared 0.04 mg/L of nanosilver until the end of the experiment. At the end of the experiment, body weight (BW), condition factor (CF), specific growth rate (SGR), feed conversion ratio (FCR), survival rate and serum biochemical parameters of glucose (mg/dl), triglycerides (mg/dl) and uric acid (mg/dl) were measured. The results showed that the nanosilver-exposed group that consumed the diet with 800 mg/kg of thyme extract had the highest percentage of weight gain (21.46 ± 0.15) and specific growth rate (0.46 ± 0.01). All nanosilver-exposed groups had lower survival rate than non-exposed groups. The condition factor (CF) in treatments that contained thyme extract in the diet was significantly higher compared with the control group (P<0.001). The lowest feed conversion ratio (FCR) was observed for the nanosilver-exposed group fed with 400 mg/kg of thyme extract. On the other hand, by reducing the concentration of thyme extract in the diet and placing the fish under nanosilver stress, we observed significantly incrased serum glucose and uric acid concentrations (P<0.001). In groups exposed to nanosilver, blood triglyceride concentrations showed a relative non-significant decrease compared to the controls. The results showed a significant, positive impact of high concentrations of thyme extract on growth factors and reduced stress in fish exposed to nanosilver.