Disinfection of hatching eggs by formaldehyde fumigation – a review Desinfektion von Bruteiern durch Begasung mit Formaldehyd – eine Übersicht

Microbial contamination of hatching eggs is a main concern of poultry producers as it causes poor hatchability and chick performance. It is evident that high standards of hygiene must be practised in hatcheries in order to minimise the soiling of eggs but, further disinfection of eggs is also necessary to limit bacterial numbers. Methods used include the application of disinfectants by wiping, spraying, and dipping but, arguably, the most effective way of disinfection of hatching eggs is fumigation with formaldehyde. Eggs can be fumigated during incubation or at pipping (during or just after the transfer to the hatcher), but most commonly prior to incubation. Formaldehyde, besides being an excellent anti-microbial agent, is also a toxic chemical and, as such, can seriously damage the dormant embryo if fumigation is carried out improperly. The part of the egg most exposed to the fumigant is the outmost organic layer, the cuticle, an important barrier to microbial invasion. Any damage of the cuticle may have serious consequences during incubation. The aim of fumigation is therefore twofold: to reduce microbial count and to minimise the adverse effects of contamination whilst causing as little damage to the developing embryo as possible. In order to fumigate effectively, the balance must be found. The importance of fumigation in hatchery practice is undoubtable, yet an overall and detailed review on the subject is still lacking. Moreover, results are sometimes conflicting or even misleading. The present review is an attempt to provide a summary of the literature on fumigation with a particular emphasis on the circumstances of this way of disinfection and the possible dangers to the developing embryo. It was also an aim to clear the contradictions and offer possible explanations for consideration. Since fumigation is usually performed prior to incubation, the following review concentrates primarily on investigations on the conditions and effects of this practice.