Impact of 2% carbon dioxide during storage on egg quality and early embryo development

Storing fertilized eggs for several weeks prior to incubation is a hatchery practice to meet fluctuating demands for chicks. However, prolonged storage leads to a progressive deterioration of the egg internal structures, which ultimately reduces hatchability. This decrease in egg quality results from an increase in albumen pH following the diffusion of CO₂ naturally present in the egg, through the eggshell pores. In this study, we explored whether a CO₂-enriched atmosphere (2%) could limit CO₂ diffusion from eggs stored for 6, 13, 20, or 27 days at 12°C and 80% relative humidity, followed by a 24-hour acclimatization at 20°C (as commonly practiced in hatcheries prior to incubation). Egg internal quality and selected blastoderm characteristics (position relative to the air cell and diameter) were evaluated using a combination of classical measurements and non-invasive imaging techniques (computed tomography and magnetic resonance imaging). A subset of eggs was incubated for seven days to evaluate embryo viability and mass. The principal component analysis revealed a clear separation between eggs stored with CO₂ and those in the control group. While storage duration negatively affected most parameters, CO₂ was shown to partly mitigate egg dehydration (as indicated by lower mass loss and air cell volume) and the progressive degradation of albumen and yolk index over time, compared with control eggs stored without CO₂. However, the size of the blastoderm was reduced significantly in CO₂ eggs following prolonged storage, compared with control eggs. This result suggests that 2% CO₂ may alter the viability of blastoderm cells. Nevertheless, no impact on the viability of embryos incubated for seven days was observed in CO₂ eggs, although they exhibited a significant decrease in embryo mass compared with control eggs. Collectively, these findings support the hypothesis that 2% CO₂ during storage prior to incubation partly prevents the degradation of internal egg components over time, but the potential benefits of this storage practice on embryonic development and growth during the entire incubation period require further investigation.