Antioxidant enzyme activities and immune responses in rainbow trout (Onchorhynchus mykiss) juveniles fed diets supplemented with dandelion (Taraxacum officinalis) and lichen (Usnea barbata) extracts

In the present study, antioxidant activity, immune responses, and growth performance of rainbow trout (Onchorhynchus mykiss) juveniles fed with diets supplemented with dandelion (Taraxacum officinalis) and lichen (Usnea barbata) extracts were assessed. Four different concentrations of aqueous methanolic extract of the plants (0% (control), 0.1%, 0.5%, and 1% (D, dandelion; L, lichen) were added to the diets, and fish were fed for 75 days. On the 15^th, 45^th, and 75^th day of the study, liver antioxidant enzyme activities were determined, and immune responses were determined every 15^th day. The results showed that SOD activity increased in the fish group of 0.1% D on the 15^th and 45^th day compared to control; however, it was lower in all the lichen extract-treated groups than in control at almost all sampling times, except on the 15^th day in the 0.1% L group. CAT activity showed an increased value (P < 0.05) in 0.5% L and 1% L treated fish groups on the 15^th day, in fish of 1% D and 1% L groups on 45^th and on 75^th day in 0.1% D group. GPX activity increased on the 15^th day of the study in fish of 0.1% D group, on the 45^th day in 1% D and 1% L groups and on the 75^th day in fish of 0.5% D, 0.1% D, and 0.5% L groups (P < 0.05). G6PDH enhanced in all treatment groups compared to control on the 15^th day, except in 0.1% L and 0.5% L groups. An elevated G6PDH activity was also observed on the 75^th day of the study in 0.5% D, 1% D, and 0.5% L fish groups. An increase on lipid peroxidation (LP) was observed in all L groups on the 45^th day of the study. Lysozyme activity was determined to be the highest in 0.5% and 1% L on the 45^th day, in 0.1% L on the 60^th day and in the 0.5% L fish group on the 75^th day compared to control (P < 0.05). Myeloperoxidase was found to be the highest at the end of the study in 1% L fish group compared to the control (P < 0.05). In conclusion, we suggest the use of dandelion to combat oxidative stress and to lower FCR and the use of lichen to modulate the immune response in rainbow trout. The use of such products will be economical for aquaculture and harmless for the environment.

Effects of ribwort plantain (Plantago lanceolata) extract on blood parameters, immune response, antioxidant enzyme activities, and growth performance in rainbow trout (Oncorhynchus mykiss)

In this study, we examined changes occurred in blood parameters, immune responses, antioxidant enzyme activities, and growth performance of rainbow trout (Oncorhynchus mykiss) administered with ribwort plantain (RP) through feed. Fish (mean weight 36.56 ± 1.99 g) were fed a diet supplemented with an aqueous methanolic extract of RP at variable doses, 0 (control), 1 (RP1), 2 (RP2), and 3 g kg^-1 (RP3) for 90 days. The final weight, weight gain, and specific growth rate were significantly increased in RP1, RP2, and RP3 treatment groups compared to that of the control. Among examined blood parameters, hemoglobin value in RP1 group (9.77 ± 0.10 g dl^-1) only was significantly high on the 30th day of the study. When immune response parameters were evaluated, we observed that oxidative radical production and lysozyme activities were affected positively in experimental groups (P < 0.05). The highest oxidative radical production was determined in fish of RP3 group. Glutathione peroxidase and glucose 6 phosphate dehydrogenase were increased in RP3 group compared to control and other treatment groups. Based on these results, it is concluded that ribwort plantain promotes growth, enhances immune responses and antioxidant enzyme activities in rainbow trout, and therefore, may be used in aquaculture.

Effect of lemon balm (Melissa officinalis) extract on growth performance, digestive and antioxidant enzyme activities, and immune responses in rainbow trout (Oncorhynchus mykiss)

This study was conducted to determine the effects of dietary supplementation of lemon balm (Melissa officinalis) aqueous methanolic extract on growth performance, blood parameters, digestive and antioxidant enzyme activities, and non-specific immune responses in rainbow trout (Oncorhynchus mykiss). Fish with an average weight of 23.03 ± 0.07 g were fed a diet supplemented with an aqueous methanolic extract of lemon balm at a dose of 0 (control), 0.1 (LB0.1), 0.5 (LB0.5), and 1 g kg^-1 (LB1) for 75 days. The final weight, weight gain, and specific growth rate were observed to be significantly increased in LB0.5 and LB1 groups compared with that of the control. No differences were observed in feed conversion ratio values. WBC increased at the 45th day of the study in LB0.1 group. No differences were determined in RBC (P > 0.05). At the end of the study, lipase increased significantly in all experimental groups compared with the control. Pepsin was also elevated in LB0.5 and LB1 groups compared with the control. Increased trypsin was determined in LB1 group (P < 0.05). SOD activity increased at the end of the study in LB1 group (P < 0.05). CAT values had no differences compared with control. GR activity increased in all experimental groups compared with control. GPx improved in LB0.5 and LB1 groups significantly (P < 0.05). Lipid peroxidation was decreased in LB1 group compared with that of control, but this decrease was not significant (P < 0.05). Oxidative radical production and lysozyme activity significantly increased in LB1 group (P < 0.05). The highest MPO was determined in control group (P < 0.05). Current results suggest that lemon balm extract stimulates growth promoting antioxidant and immune responses in rainbow trout.