Field Safety and Efficacy of in ovo Administration of HVT + SB-1 Bivalent Marek's Disease Vaccine in Commercial Broilers

Abstract

The field safety and efficacy of a bivalent Marek's disease (MD) vaccine (herpesvirus of turkeys + strain SB-1) administered in ovo were evaluated. The vaccine was administered to commercial broiler chicken eggs using Embrex's INOVOJECT automated egg-injection system. Comparisons were made with a conventional method of vaccination, in which the vaccine was administered subcutaneously to chicks at hatching. In ovo administration of the vaccine at day 17.5-18.5 of incubation significantly reduced the number of culled chicks, early mortality, and overall mortality during the grow-out period compared with conventional vaccination. However, hatchability was significantly lower in in ovo-treated chicks. Overall livability and feed efficiency were higher in the in ovo-treated chicks than in conventionally vaccinated chicks. Total field-caused condemnations and condemnations due to airsacculitis and septicemia/toxemia were also lower in the in ovo-vaccinated chicks. No difference in the leukosis (MD) condemnation rate was observed between the two treatment groups. In ovo vaccination provided 93.25% protection against challenge with a very virulent strain of MD virus (strain RB1/B); by comparison, the conventional vaccination method provided 89.58% protection.