# Alternative protocols for sanitizing hatching eggs and their effects on the microbiota of eggshell surface and chick yolk sac

## TL;DR

This study tested different egg sanitization methods and found that UV-C irradiation and peracetic acid reduce harmful bacteria on hatching eggs and chick yolk sacs.

## Contribution

The study identifies UV-C and peracetic acid as effective, formaldehyde-free alternatives for reducing bacterial contamination in hatcheries.

## Key findings

- UV-C irradiation and peracetic acid reduced Staphylococcus on eggshells.
- Peracetic acid also decreased Escherichia in chick yolk sacs.
- Proteobacteria, especially Staphylococcus and Escherichia, dominated the eggshell and yolk sac microbiota.

## Abstract

This study aimed to evaluate the effect of different sanitization procedures on the eggshell surface and yolk sac microbiota of one-day-old chicks. Hatching eggs were collected from a 70-wk-old Cobb500® commercial broiler breeder flock and distributed in a completely randomized design with seven treatments: fumigation with paraformaldehyde (4.63 g/m3/30 min; FORM), fumigation with ozone (5-15ppm/30 min; Ozone), ultraviolet light-C irradiation (8.09 mW/cm2; 120 s; UV-C), hydrogen peroxide spraying (3%; 0.69 mL/egg; H2O2), peracetic acid spraying (0.3%; 0.69mL/egg; PAC), water spraying (0.69mL/egg; Water) and without sanitization (dry control - Dry). Culture-dependent methodology was carried out to isolate the microorganisms from eggshell surface (n = 224) and yolk sac in one-day-old chicks (n = 91), followed by identification by mass spectrometry (MALDI-TOF). Proteobacteria phylum was dominant on egg structures evaluated, with nineteen genera identified on the eggshell surface and twelve in the yolk sac. The most abundant genera found on eggshell surfaces and in yolk sacs were Staphylococcus spp. (18%) and Escherichia spp. (32.6%), respectively. Among the sanitization protocols tested, ultraviolet light-C irradiation and peracetic acid spraying decreased the presence of Staphylococcus spp. and Escherichia spp. in hatching eggs. Eggshell and yolk sac microbiota of newly hatched chicks were dominated by Staphylococcus and Escherichia species, respectively. UV-C irradiation and peracetic acid effectively reduced eggshell Staphylococcus, with peracetic acid also decreasing yolk sac Escherichia. These findings support UV-C and peracetic acid as effective alternatives to formaldehyde in commercial hatcheries.

The online version contains supplementary material available at 10.1007/s42770-026-01896-x.