Effects of essential oil of Magnolia denudata on spotted seabass (Lateolabrax maculatus) during simulated live transportation

The essential oil of Magnolia denudate (MDO) is an effective anesthetic and sedative on spotted seabass (Lateolabrax maculatus). To improve animal welfare and transportation effectiveness, this study evaluated the effects of MDO on water quality, blood biochemical, and tissue damage after the transportation of L. maculatus (164.16 +/- 15.40 g). A base group (no MDO and no transport) and 0 (control group), 10, and 20 mg/L MDO during simulated transportation treatments of 5 h were involved. Every treatment has four replicates with four fish transported in a plastic box (34 x 22.5 x 19 cm) with 5 L water at a fish density of 130 g/L and a shake rate of 60 rpm. At the end of the transportation simulation, no mortality was observed. Fish were immediately sampled for blood collection, liver and brain removal. Compared to the control group, the MDO groups showed significantly lower ammonia in water, lower cortisol level and lactic dehydrogenase activity, higher glucose, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase activities in fish serum (p < 0.05). Superoxide dismutase (SOD), catalase (CAT) activity, glutathione (GSH) concentration decline, and malondialdehyde (MDA) were alleviated in the fish brain when MDO was added to the water. However, SOD and GSH further decreased, but MDA increased in the fish liver in the MDO groups (p < 0.05). These results revealed that the administration of MDO on L. maculatus transportation could alleviate stress and decrease energy metabolism. Due to the 20 mg/L MDO may trigger more serve liver function decline, we suggest 10 mg/L MDO addition in L. maculatus transportation.