Studies on performance, immunity, and safety of broilers vaccinated with killed H9N2 vaccine and supplemented with essential oils of mentofin® in drinking water

The aim of this research is to evaluate the effect of intermittent administration of essential oil of Mentofin® on immunity, blood parameters, and growth performance of unvaccinated and vaccinated broilers, administered killed H9N2 vaccine followed by controlled challenge with homologous strain of the virus,. Two hundred and forty SPF day-old broiler chicks (Ross 308) were subjected to a completely randomized design, by allocating them to five treatments (A-E), with four replicates/treatment, and 12 birds/ replicate. Birds in treatments D and E were vaccinated subcutaneously at seven days of age. Mentofin® was administered intermittently in drinking water to broilers in treatments C and D. An intranasal challenge with H9N2 was administered at 28 days of age to birds in treatments B, C, D and E. Results showed that birds in treatment D, vaccinated and treated with Mentofin® and challenged, had the lowest heterophil count and lowest Heterophil/lymphocyte ratio among all challenged birds of the other treatments. In addition, birds in treatment D, compared to all challenged birds, had the highest HI titer associated with lowest enzyme blood profile. Moreover, birds of treatment D had the highest live body weight and lowest feed conversion at 42 days of age compared to birds of all other treatments. In conclusion, the essential oil of Mentofin® in birds of treatment D proved its immunopotentiating effect, with lowest heterophil reaction, thus alleviating injuries of the challenge, as shown with lowest blood enzyme profile, lowest feed conversion ratio and highest live body weight.