Résumé
Aims: The aims of this study were to characterize the antibacterial activity andthe chemotype of Litsea cubeba leaf essential oil (EO) harvested in NorthVietnam and to investigate the biological effects induced by the leaf powder ongrowth, nonspecific immunity and survival of common carp (Cyprinus carpio)challenged with Aeromonas hydrophila.Methods and Results: The EO showed the prevalence of linalool (95%,n = 5). It was bactericidal against the majority of tested strains, with minimuminhibitory concentrations ranging from 072 to 289 mg ml1 (Aer. hydrophila,Edwarsiella tarda, Vibrio furnissii, Vibrio parahaemolyticus, Streptococcusgarvieae, Escherichia coli, Salmonella Typhimurium). The fish was fed with 0(control), 2, 4 and 8% leaf powder supplementation diets for 21 days.Nonspecific immunity parameters (lysozyme, haemolytic and bactericidalactivities of plasma) were assessed 21 days after feeding period and before theexperimental infection. Weight gain, specific growth rate and feed conversionratio were improved by supplementation of L. cubeba in a dose-relatedmanner, and a significant difference appeared at the highest dose (8%) whencompared to the control. The increase in plasma lysozyme was significant forall the treated groups. Haemolysis activity was higher for the groups fed with 4and 8% plant powder. Antibacterial activity increased significantly for the 8%dose only.Conclusions: Litsea cubeba leaf powder increased nonspecific immunity ofcarps in dose-related manner. After infection with Aer. hydrophila, survivals offish fed with 4 and 8% L. cubeba doses were significantly higher than those fedwith 2% dose and the control.Significance and Impact of the Study: A range of 4–8% L. cubeba leaf powdersupplementation diet (from specific linalool-rich chemotype) can be used inaquaculture to reduce antibiotic burden and impacts of diseases caused byAer. hydrophila.