Effect different concentrations of hydro-alcoholic Aloe vera )Aloe brabadensis) extract by bath therapy on blood indices and immune responses and control of saprolegniasis in rainbow trout

The aim of this study was to evaluate the effect of hydroalcoholic extract of Aloe vera plant by bath therapy on immunological and blood parameters and control of saprolegniasis in rainbow trout (Oncorhynchus mykiss). After two weeks of adaptation, fish with an average weight of 22±0.27g were randomly divided into 6 experimental treatments with three replications (30 fish repetitions each). After scaling from the caudal fin, the fish were infected with 3×105 zoospores of Saprolegnia parasitica per litter for 4 hours. After that, four treatments received 50, 100, 150 and 200 mg/L Aloe vera hydroalcoholic extract for one hour daily for one week. The other two treatments belonged to the positive control groups (with infection and without Aloe vera treatment) and the negative control group (without infection and without Aloe vera treatment). Evaluation of hematological and immunological parameters at the end of one week of bathing with the above concentrations (first week) and one week after cessation of bathing (second week) showed that hematological, biochemical and immunological parameters of rainbow trout (O. mykiss) treated with 100 mg/l Aloe vera hydroalcoholic extract was significantly increased. Also, at this concentration of hydroalcoholic extract of Aloe vera, minimal losses were observed, which was statistically significant compared to the control group. According to the results, treatment of rainbow trout with saprolegniasis with 100 mg of hydroalcoholic extract of Aloe vera per litter can improve immune function and increase their survival against saprolegniasis.