Vaccination plays an important part in the health management of the poultry flock. There are numerous diseases that are prevented by vaccinating the birds against them. Vaccination is a way of obtaining a controlled result with a minimum of harm to the birds. Vaccines are generally fragile products some of which are live but in a state of suspended animation. The aim of this study was to assessment of preventive effect of thyme essential oils in the vaccination reactions in chickens. In this study, 450 one year old Lohman chicks were selected. Chicks were divided into 5 groups. From day 1 to end of the study, thyme essence was used as mentioned in materials and method section. The results showed that there were low reactions in treatment than control group. Thus can be conclude that thyme essence has protective effect in emergence the vaccination reactions.
