AimTo evaluate the impact of Eucalyptus and peppermint essential oils on immune modulation and production of broiler chicken challenged with a molecularly characterized velogenic NewCastle disease virus (vNDV). Methods and ResultsThe experimental design included five treatments with three replicate pens/treatment comprised of 12-day-old broilers chicks/replicate. The five treatments included a positive challenge control (non-NDV vaccinated/nonessential oil treated/challenged) (NNEOC), a negative challenge control (NDV vaccinated/essential oil treated/unchallenged) (VEOU), a non-NDV vaccinated/essential oil treated/challenged (NEOC), a NDV vaccinated/nonessential oil treated/challenged (VNEOC) and a NDV vaccinated/essential oil treated/challenged (VEOC). The lowest mean survival rate (00%) and lowest production performance were obtained by the positive challenge control, while the best mean survival (933%) and average body weight (2649g) were obtained by the negative challenge controls (P<005). Among the three others challenged treatments, the best mean survival (792%), highest mean body weight at 42days of age (2445g), the lowest feed conversion ratio (160) and the highest serum conversion immunopotentiation at 35days of age determined by ELISA and hemagglutination titres were obtained by the VEOC birds compared with respective means obtained by birds of the NEOC and VNEOC treatments (P<005). ConclusionsThe results supported the possibility of using the essential oils of Eucalyptus and Peppermint in broilers to immunopotentiate the response to vaccination against velogenic NDV, helping in significant improvement of survival and production. Significance and Impact of the StudyThis study provides information about the potential use of essential oils of eucalyptus and peppermint that can be exploited as commercial immunopotentiators for the protection of NDV-vaccinated broiler chickens against economic velogenic NDV.