Value and Limitations of Formaldehyde for Hatch Cabinet Applications: The Search for Alternatives

*Danielle B. Graham, Christine N. Vuong, Lucas E. Graham, Guillermo Tellez-Isaias and Billy M. Hargis*

## **Abstract**

Pioneer colonization by beneficial microorganisms promote a shift in the composition of the gut microbiota, excluding opportunistic pathogens. Commercially, the horizontal transmission of both apathogenic and pathogenic organisms is common during the hatching phase. The microbial bloom occurs as the humidity rises during hatch, exposing naïve chicks to a plethora of potentially harmful microbes. Horizontal transmission or introduction of pathogens may occur as infected chicks hatch or during handling after hatch pull. Moreover, contaminated infertile or non-viable embryonated eggs can serve as reservoirs for pathogenic organisms and even rupture during incubation. The organisms within the contents of these eggs can penetrate the shell of the embryonated eggs and subsequently contaminate the entire cabinet. Formaldehyde fumigation is commonly applied during the hatching phase to control the microbial bloom in the environment, but does not penetrate the eggshell prior to hatch. Additionally, this fumigation technique eliminates microbial organisms in the environment at hatch, including beneficial species. Furthermore, prolonged exposure to formaldehyde can damage the tracheal epithelia of neonatal chicks increasing susceptibility to infection by opportunistic microbes. Laboratory challenge models that mimic the microbial bloom that occurs in commercial hatch cabinets can be used to evaluate effective alternatives to control the microbial bloom and promote colonization by beneficial bacteria without the use of formaldehyde fumigation.

**Keywords:** hatchery, microbial bloom, pioneer colonization, model

### **1. Introduction**

Horizontal transmission of pathogens during the neonatal period is a major concern to commercial poultry producers. In a commercial setting, viable eggs are removed from hens and transported to a hatchery for artificial incubation. Eggs from multiple source flocks are frequently comingled during incubation which promotes both cross-contamination of pathogens as well as exposure to potential beneficial

pioneer colonizing bacteria. At 18 days of embryogenesis (DOE), embryos are transferred from incubators to hatch cabinets with holding capacities exceeding 10,000 embryos. At approximately DOE20, or initiation of the hatching process, chicks begin to pip and break through the eggshell. As chicks pip, they are exposed to microbes on the surface of the eggshell [1]. Fecal material on the surface of the eggshell may harbor potential pathogenic microbes capable of penetrating the eggshell and membranous layers during incubation [1]. Eggshell contamination has been shown to negatively impact hatchability and hinder early performance [2]. Additionally, these contaminated embryos serve as reservoirs that horizontally transmit pathogens during the hatching phase [3]. As chicks hatch, the humidity in the hatching environment promotes replication of both apathogenic and pathogenic microbes. The composition of the microbial bloom during the hatching phase influences pioneer colonization of the neonatal gastrointestinal tract [4]. As such, cross-contamination of primary poultry pathogens readily occurs in commercial hatcheries [5]. Prior to incubation, chemical sanitizers may be used to reduce the microbial load on the surface of the eggshell to prevent cross-contamination during embryogenesis [2, 6, 7].

For over a century, formaldehyde fumigation has been utilized to control the dissemination of pathogens in some commercial hatcheries [8, 9]. Although formaldehyde eliminates microbes in the hatching environment, it has been associated with tracheal epithelial damage and mucosal sloughing in neonatal chicks [10–12]. As a biocide, formaldehyde effectively kills resistant forms of bacteria, fungi, and viruses [13], and likely eliminates airborne apathogenic and potentially beneficial microbes. Cost-effective and sustainable alternatives to formaldehyde fumigation to reduce microbial load in the hatching environment are needed. However, a multi-faceted approach will be required to control the microbial bloom in the hatching environment and promote early colonization by beneficial microbes to improve poultry health.
