LAUSR

The study evaluated the effects of intramuscular injection of butaphosphan and cyanocobalamin combination (BPC) on the plasma levels of cortisol, cytokines, and the activities of selected enzymes in Oliveflounder exposed to crowding stress. Three groups of fish (n = 12 per group) were kept in different glass tanks with stocking densities of 46 kg/m³(group BP and SCH) and 15 kg/m³ (group SCL). Group BP was treated with 0.5 ml of BPC. While groupSCH and SCL were treated with 0.5 ml of saline. Blood was collected a day after injection (T1), and weekly for two consecutive weeks (T2 and T3). The plasma levels of interleukin (IL) ‐1β, IL‐6, cortisol, lysozyme, and the activities of aspartate aminotransferase (AST) and alanine transaminase (ALT)were determined using an ELISA kit. The statistical significance of differences was assessed using ANOVAfollowed by Tukey‐HSD test (P < 0.05 considered significant).A significantbody weight gain was measured in the BP and SCL groupscompared with SCH at T3. The activities of AST (at T1, T2, and T3) and ALT (at T1 and T2) were declined significantly (P < 0.05) following treatment of overcrowded fish with BPC than saline. Similarly, BPCcaused a significant reduction in the levels of cortisol and IL‐1β at T2 and T3.This is the first report of the effect of the combination of butaphosphan and cyanocobalamin on plasma immune and biochemical parametersin fish. Therefore, the combination could be beneficial in preventing overcrowding‐induced immune suppression and tissue damage in Olive flounder.