Proper egg storage is a critical factor influencing the efficiency and success of poultry production. The period between egg collection and incubation can have significant effects on egg quality, embryo development, and eventual hatchability. Variations in storage conditions and duration can alter internal egg characteristics, impacting the viability of embryos and the uniformity of chicks. Among the factors affecting these outcomes, storage duration and breeder age play particularly important roles, often interacting in complex ways that determine overall reproductive performance (Christensen et al., 2001; Reijrink et al., 2008; Tona et al., 2003).
Influence of hatching egg storage duration on egg characteristics
Moisture transfer and weight changes
– During storage, moisture moves from the albumen to the yolk, and some water is lost through evaporation via the shell.-
– As a result, albumen weight decreases, while yolk weight increases (Jin et al., 2010).
– The increase in yolk percentage is mainly due to this water movement and the general loss of total egg weight.
Chemical exchanges across the vitelline membrane
– During extended storage (>14 days), free amino acids move from yolk to albumen, and additional moisture moves from albumen to yolk, lowering yolk solids concentration.-
– These exchanges are enhanced by weakening of the vitelline membrane, linked to rising albumen pH over time (Li-Chan et al., 2017).
Albumen and yolk quality deterioration
– The dense albumen liquefies as CO₂ escapes through the shell, raising pH from about 7.6 (fresh) to 9.0–9.5 (stored) after a few days (Freeman and Vince, 1974).-
– The increase in pH destabilizes the ovomucin–lysozyme complex, leading to reduced viscosity, thinning of the albumen, and lower Haugh units a key measure of egg quality.
– The greatest loss of viscosity happens during the first few days of storage, paralleling the sharp rise in pH.
– The yolk pH stays relatively constant (≈6.5), but its moisture content increases, raising the yolk index (Heath, 1975).
Effect of breeder age
– Younger flocks’ eggs deteriorate faster in albumen quality during storage than those from older flocks.
– Eggs from young breeders start with higher initial Haugh unit scores (better quality) but show a steeper decline in albumen quality and faster pH increase during storage (Lapaõ et al., 1999).
Influence of egg storage on embryo development and hatching performance
Effects on early embryo development
– At oviposition, a healthy chicken blastoderm contains about 60,000 cells and is typically at developmental stage EG10–EG12 (EG means stages of early development of embryos according to Eyal-Giladi and Kochav, 1976)
– Prolonged storage does not change morphological stage but slows overall embryonic cell development; even after 28 days, embryos only reach up to stage EG13, indicating developmental arrest (Pokhrel et al., 2018).
– Lower storage temperatures (5–15°C) induce temporary cell cycle arrest (mitotic phase), which helps protect cells from death and supports post-incubation recovery (Pokhrel et al., 2018).
– However, long storage leads to cellular aging and rising apoptosis rates, decreasing the number of viable blastodermal cells (Hamidu et al., 2011).
Cell viability and apoptosis
– The percentage of apoptotic (dying) cells rises sharply with storage:
– From 3.1% at lay to 13.9% after 14 days at 12°C (Bloom & Muscarella, 1998).
– Viable cells drop from 81% (4 days storage) to 68% (14 days) (Hamidu et al., 2011).
– Increased apoptosis and reduced viable cell counts limit the embryo’s ability to initiate and sustain normal development, raising the risk of malformations and embryonic death (Christensen et al., 2001).
Developmental delay and metabolism
– Long storage delays the onset and rate of embryonic development, leading to later hatch times and slower cell proliferation.-
– Reduced viable cell numbers mean lower oxygen uptake and metabolic activity, which slows energy production needed for organ growth and contributes to smaller embryos and chicks (Christensen et al., 2001; Hamidu et al., 2011).
– Embryos from long-stored eggs show lower CO₂ production, reflecting slower metabolism (Uddin & Hamidu, 2014).
Impact on embryo weight and chick quality
– Embryo and chick weights decrease as storage duration increases (Bakst et al., 2016).
– Chick length and weight decline linearly with storage beyond 10–12 days, though hatchling quality scores (e.g., Tona score) often remain unchanged for moderate storage durations (Goliomytis et al., 2015).
– Negative chick quality effects become noticeable mainly after very prolonged storage (≥21–28 days).
Egg weight loss and hatchability
– Egg weight loss increases with longer storage, mostly due to water evaporation before incubation (Fasenko et al., 2001).
– Hatchability generally declines after 7 days of storage, often at a rate of about 1–1.5% per additional day, mainly because of higher early and late embryonic mortality (Schmidt et al., 2009).
– Nonetheless, short storage (3–7 days) can slightly improve hatchability, especially for young breeder flocks, by reducing albumen viscosity and improving oxygen diffusion to the embryo (Benton and Brake, 1996).
– After extended storage, oxygen limitation and cell damage outweigh any benefit, causing a consistent drop in hatch rates.
Interactions of hatching egg storage duration with breeder age
Embryo quality and developmental stage
– Embryo development at oviposition differs by breeder age: embryos from younger flocks (32 weeks) are usually at stage EG10–11, while those from older flocks (63 weeks) are more advanced (EG12+) (Pokhrel et al., 2018).
– Embryos from older breeders are more advanced and contain more viable cells, which may make them more resilient to cell death (apoptosis/necrosis) during moderate storage.
– However, storage negatively affects embryo quality more severely in older flocks, leading to more malformed embryos after prolonged storage (14 days) (Mather and Laughlin, 1979).
– Studies show that storage-induced quality loss is greater in embryos from older breeders, for example, a larger reduction in saleable chicks after 7 days of storage (−14.3% vs. −0.81% for young flocks) (Tona et al., 2004).
– Once embryos survive and resume development after storage, hatchling physical traits (weight, length, yield) are generally not affected by breeder age or storage duration interaction (Pokhrel et al., 2018).
Embryo metabolism and pH regulation
– Older-flock embryos have greater metabolic activity at oviposition and can produce more CO₂, helping to regulate the microenvironmental pH closer to optimal levels (<9).
– This enhanced metabolism may make older embryos more stable early in incubation, but prolonged storage increases cell activity and energy demand, depleting reserves and promoting cell death over time.
– Younger-flock embryos, being less advanced, may initially tolerate short-term storage better because of lower metabolic demands, but extended storage overwhelms cellular viability in both age groups (Pokhrel et al., 2018).
Egg weight loss
– Eggs from older breeders lose more water during storage and incubation due to poorer albumen quality, thinner shells, and faster albumen liquefaction (Lapaõ et al., 1999).
– This higher evaporation rate can increase embryo dehydration risk, contributing to lower hatchability in older breeder eggs after long storage.
Hatchability trends
– Short storage (up to ~7 days) can slightly improve hatchability in eggs from young breeders but not in older ones.
– Prolonged storage (>7–10 days) causes a clear decline in hatchability, more pronounced in older flocks.
– For example, at 30 weeks of age, hatchability dropped by only 2%, while at 53 weeks it fell by over 10% over similar storage durations (Elibol et al., 2002).
– The rate of hatchability decline accelerates with breeder age — beyond 14 days, older-flock eggs show sharper increases in embryonic mortality (Pokhrel et al., 2018).
– Therefore, it is preferable to store eggs from younger flocks when longer storage is unavoidable (Lapaõ et al., 1999).
Conclusion
In conclusion, the importance of proper hatching egg storage lies in its decisive influence on both egg quality and embryo viability, which ultimately determine hatchability outcomes. Prolonged storage periods (beyond 7 days) consistently lead to deterioration in albumen quality, increased embryonic cell death, and reduced hatchability particularly in eggs from older breeder flocks (>50 weeks). It is therefore essential to adapt storage practices to breeder age, balancing temperature, humidity, and duration to preserve embryo vitality. By optimizing these conditions, hatcheries can minimize developmental delays, maintain high hatching performance, and ensure uniform chick quality. Once embryonic development successfully resumes after storage, further growth generally proceeds normally, underscoring the critical value of age-specific and time-sensitive egg storage management in maximizing overall incubation success.
References
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