Effect of in ovo inoculation of 18 day incubated embryonated broiler eggs with Escherichia coli and Enterococcus faecalis on hatchability, chick quality and first week performance

Abstract

A relative new technique in prevention of infectious diseases in poultry is in ovo vaccination, which has been used in the poultry industry since 1992. When injecting a vaccine in ovo, there are several factors which can alter the impact on the hatchability of the eggs. These factors include the characteristics of the vaccine, the injection technique and the overall hygiene of the hatchery. Bacterial contamination of embryonated eggs can impair hatchability and chick quality and lead to a higher first week mortality. The aim of this study was to discover which bacterial strains (mildly and very virulent strains of Escherichia coli and Enterococcus faecalis), in which dose (10^2, 10^4 or 10^6 colony forming units [cfu]/egg) and via which inoculation route (amniotic cavity or embryo) affected hatchability, chick quality and first week performance most. Hereto, 18 day incubated embryonated broiler eggs were inoculated with 0.1 ml bacterial suspension. Hatching rate, time of hatch, chick length, Pasgar score, mortality, time of death and weight at the end of the experiment were used as parameters. The results showed that hatch and first week mortality is affected by different bacteria and combinations, in all inoculated doses and by both inoculation routes. There was, however, no difference observed between inoculation routes. Chick quality did not seem to differ with the control groups, nor between the groups inoculated with bacteria. Strict aseptic measures should therefore be taken in hatcheries to avoid contamination of eggs with very virulent bacteria, such as Escherichia coli and Enterococcus faecalis, in low doses (10^2 cfu/egg).