Investigation of the possible effects of some medicinal plants as an immunostimulant and antioxidant on rainbow trout (Oncorhynchus mykiss)

This study was designed to evaluate the growth, digestive enzyme activity as well as some antioxidant, immunological and haematological parameters of rainbow trout juvenile fed diets containing different levels (0%, 0.1%, 0.5% or 1%) of Glycyrrhiza glabra, Coriandrum sativum, Cassia angustifolia aqueous methanolic extract as a feed additive seventyfive days. During the study, in addition to antioxidant enzyme system and digestive enzymes, methanolic extracts were investigated for immunity, hematological parameters and growth effects. The fish with initial weight of 22.65 ± 0.07 g were divided into 30 tanks so that 10 groups would be formed and stored as 50 fish in each tank, so the experiment was started as three replications. At the end of every month, respiratory burst (NBT), lysozyme and myeloperoxidase (MPO) activity as well as liver antioxidant enzyme activities (catalase, CAT; superoxide dismutase, SOD; glutathione peroxidase, GPx and GSH) and lipid peroxidation level (melondialdehyde, MDA) were analyzed. After seventyfive days of feeding, growth parameters such as final weight, weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR) and digestive enzymes like pepsin, trypsin, amylase and lipase as well as haematological profile; red blood cells (RBC) count, hemoglobin content (Hb), haematocrit value (Hct) and red blood cells indices including; the mean cell volume (MCV), mean cell hemoglobin (MCH) and mean cell hemoglobin concentration (MCHC) were examined. According to the results of the study, methanolic extracts of C. sativum and C. angustifolia significantly increased SOD activity in rainbow trout (P <0.05), but did not show any significant change in CAT activity (P>0,05). Increased dose GSH levels of 1% of all experimental groups (P <0.05). When GPx levels were compared, C. sativum and C. angustifolia showed an overall increase in lipid peroxidation compared to the control, while lipid peroxidation was generally low in the experimental groups (P <0.05). Amylase, lipase, pepsin and trypsin are different in terms of enzyme activities, but generally these enzyme activities are related to the control group. NBT values were higher in all experimental groups than control group (P <0,05), LYS and MPO values were lower than control at the end of the experiment (P <0,05). For all haematological parameters, the values related to the growth parameters were lower than the control group in the study where similar or low values were encountered. As a result, in terms of antioxidant and digestive enzymes, these plants generally have an advantage, while the positive effects of the fish on their immune, hematological and growth parameters are often lacking.