A fertilized egg represents the initial stage of a new organism, formed by reproductive cell fusion. Unlike unfertilized eggs, they contain a developing embryo. While continued development requires specific external conditions, particularly warmth, they can temporarily halt this process, surviving periods without consistent heat. This allows a pause until favorable conditions return.
The Science of Dormancy
The ability of fertilized eggs to survive without continuous heat is due to embryonic diapause, a state of suspended animation. When temperatures fall below a specific threshold, known as “physiological zero,” the embryo’s metabolism significantly slows. For chicken embryos, this is around 21°C.
In this dormant state, cellular activity and division are greatly reduced. This metabolic slowdown conserves egg resources, allowing the embryo to remain viable without developing. This survival strategy ensures development resumes only when environmental conditions are conducive to hatching and growth.
Factors Influencing Survival
Several factors determine how long a fertilized egg remains viable. Temperature is significant; the ideal storage range is 12-18°C. Too-high temperatures cause unbalanced development and embryo death; too-low temperatures can lead to cellular damage or freezing.
Humidity is also important, as eggs lose moisture through their porous shells. A relative humidity of 70-85% is recommended to prevent embryo dehydration, significantly reducing viability. Egg quality and age (parent bird health and genetics) also impact survival. Eggs from younger breeder flocks tend to withstand prolonged storage better. Survival durations also vary between different bird species.
Typical Survival Durations
For poultry like chickens, fertilized eggs can be stored without heat for 7-10 days under proper conditions. After this period, hatchability declines noticeably, by 0.5% to 1.5% per day. While some chicken eggs remain viable for up to 14 or even 21 days, hatching success drops significantly with extended storage.
For optimal results, incubate chicken eggs within a week of being laid. Eggs stored for longer periods, such as 10 days, show increased embryo mortality and impaired embryo growth even after incubation begins. This decline is attributed to changes within the egg, including albumen quality and vitamin/membrane breakdown.
Maximizing Viability for Hatching
Proper storage of fertilized eggs is important for optimal hatch rates. Maintaining a consistent temperature between 12-18°C and a relative humidity of 70-85% is ideal. Avoiding sudden temperature fluctuations is also advised, as this negatively impacts embryo viability.
Store eggs with their large end facing upwards. This helps position the air cell and prevents yolk adherence to the shell membrane. For storage exceeding a few days, gently turn eggs daily by 45-90 degrees to prevent yolk settling and embryo sticking. Handle eggs with clean hands to minimize bacteria.