Impact of formaldehyde application in commercial hatchers on chick intestinal microbiota

Reducing microbial contamination during late-stage incubation is important for hatchery sanitation and early chick microbial exposure. Formaldehyde is commonly applied in commercial hatchers to reduce airborne and eggshell-associated microorganisms. However, its effect on intestinal microbial recovery during late incubation and hatch remains unclear. The objectives of this study were to compare commercial hatchers with or without formaldehyde application for effects on embryo and chick intestinal microbial counts and airborne microbial loads. Two trials were conducted using commercial broiler hatching eggs. Intestinal and air samples were enumerated on TSA, MSA, BEA, EMB, TSA-anaerobic, and EYA media. Analysis showed that sampling day, rather than formaldehyde treatment, was the dominant factor associated with intestinal microbial recovery. In Trial 1, significant temporal increases were observed across multiple days for TSA and TSA-anaerobic in both treatments, with additional increases on EMB, BEA, and EYA depending on treatment (adjusted p < 0.05). In Trial 2, most media remained low through d 20 and increased significantly by d 21 in both treatments, including TSA, MSA, BEA, EMB, TSA-anaerobic, and EYA (adjusted p < 0.05). Air plate enumeration was descriptive only, but airborne counts generally increased from d 19 to d 21 in both hatchers, with only limited apparent reduction during formaldehyde exposure. Overall, the commercial formaldehyde application program evaluated here did not prevent the hatch-associated increase in cultivable intestinal microbiota and appeared to provide only limited short-term suppression of microbial recovery in the hatcher environment.