Effects of litter treatments and broiler breeder flock age on hatchability and microbial composition of eggshells, egg membranes and egg contents

Gábor Csitári¹Nikoletta Such²László Menyhárt³Kornél Schermann²Kornél Humpok⁴Valéria Farkas²László Pál²Karoly Dublecz^5*

• ¹Institute of Physiology and Nutrition, Hungarian University of Agricultural and Life Sciences, Gödöllő, Hungary
• ²Institute of Physilogy and Nutrition, Hungarian University of Agricultural and Life Sciences, Gödöllő, Hungary
• ³Institute of Mathematics and basic Sciences, Hungarian University of Agricultural and Life Sciences, Gödöllő, Hungary
• ⁴Gallus Ltd., Devecser Levente telep 1, Hungary
• ⁵Hungarian University of Agricultural and Life Sciences, Gödöllő, Hungary

Floor eggs represent a significant loss for broiler breeder farms and hatcheries due to the increased risk of bacterial contamination of embryos, the hatchery environment, and newly hatched chicks. In this trial, the effects of litter exposure duration (3, 6, and 16 hours) and breeder flock age (22–23 weeks vs. 65–66 weeks) were evaluated in terms of hatchability and the microbial composition of different egg components (eggshell, egg membrane, and egg content).The number of total culturable aerobic microbes on the eggshell surface increased following litter exposure and plateaued after 3 hours. Hatchability, however, was significantly reduced only after 16 hours of exposure, primarily due to increased embryonic mortality.Litter exposure and flock age led to significant differences in microbiota composition, but only on the eggshell surface. At the phylum level, 16 hours of litter exposure significantly increased the abundance of Firmicutes and decreased that of Proteobacteria. At the genus level, litter exposure resulted in increased relative abundances of Lactobacillus and Ruminococcus torques group, and a decreased abundance of Staphylococcus.The microbiota of the egg membrane and egg content were similar at the phylum level, though notable differences were observed at the genus level. Pseudomonas was dominant in the egg membrane but underrepresented in the egg content, leading to a significantly higher abundance of spoilage-associated bacterial genera in the membrane compared to the content. Interestingly, the genus Flexivirga (phylum Actinobacteria) was detected in high abundance in both the egg membrane and egg content, despite not having been previously reported inside eggs.According to the results, no measurable bacterial translocation occurred from the litter into the internal egg structures. However, the frequency of floor egg collection may be a critical factor if such eggs are intended for hatching.