How Long Can Fertilized Eggs Survive Without Heat?

Fertilized eggs are the result of a successful mating between male and female birds. These eggs contain embryos that, under the right conditions, will develop into healthy chicks. One essential factor for successful incubation is heat. In this article, we will discuss the importance of heat during the incubation process and explore how long fertilized eggs can survive without heat.

Factors Affecting Egg Survival Without Heat

Embryo Stage

The stage of embryo development plays a crucial role in determining how long a fertilized egg can survive without heat:

  1. Early development: During the first few days, the embryo is more resilient to temperature fluctuations.
  2. Mid development: As the embryo develops further, it becomes more sensitive to temperature changes.
  3. Late development: In the final stages of development, the embryo is highly sensitive to temperature fluctuations and requires consistent heat to ensure a successful hatch.

Temperature Fluctuations

The impact of temperature changes on egg survival depends on the duration and degree of exposure:

  1. Short-term exposure: Fertilized eggs can tolerate brief periods of temperature drops, but the hatch rate may decrease if the exposure is too frequent or severe.
  2. Long-term exposure: Extended periods of low temperatures can lead to embryo death, especially if the egg is in the later stages of development.

Humidity Levels

Proper humidity is crucial for maintaining the health of the embryo:

  1. Low humidity: Dry conditions can lead to excessive moisture loss from the egg, causing the embryo to become dehydrated.
  2. High humidity: Excessively high humidity can prevent the necessary moisture loss, leading to an underdeveloped air cell and difficulty hatching.

Eggshell Quality

The quality of the eggshell can affect how well the egg maintains heat:

  1. Thickness: Thicker shells provide better insulation, helping the egg retain heat.
  2. Porosity: More porous shells lose heat more quickly, which can make the egg more susceptible to temperature fluctuations.

Timeframe of Egg Survival Without Heat

Early Stages of Development

During the first 48 hours of development, fertilized eggs are more resilient to temperature drops:

  1. First 24 hours: Eggs can generally survive without heat for up to 6 hours, but hatch rates may decrease if the temperature drops too low.
  2. First 48 hours: After 48 hours, the embryo becomes more sensitive to temperature fluctuations, and the risk of death increases with each passing hour without heat.

Mid Stages of Development

From Day 3 to Day 14, embryos become more sensitive to temperature changes:

  1. Day 3 to Day 7: Fertilized eggs can typically survive without heat for 2-4 hours, but prolonged exposure to low temperatures can lead to embryo death.
  2. Day 8 to Day 14: At this stage, the embryo is even more sensitive to temperature fluctuations. Eggs can only survive without heat for 1-2 hours before the risk of death increases significantly.

Late Stages of Development

In the final stages of development, embryos are highly sensitive to temperature changes:

  1. Day 15 to Day 18: Eggs can typically survive without heat for less than an hour. Prolonged exposure to low temperatures can cause severe developmental issues or death.
  2. Day 19 to Hatching: During this critical period, even brief temperature drops can be fatal. It is essential to maintain consistent heat to ensure a successful hatch.

The Impact of Cooling Periods on Hatchability

  • The importance of cooling periods: Some cooling periods can be beneficial, as they mimic the natural incubation process where the mother bird leaves the nest periodically. These breaks can help promote proper embryo development and increase hatch rates.
  • How cooling periods affect hatch rates: Cooling periods can help regulate the embryo’s metabolism, ensuring it doesn’t grow too quickly or slowly. However, excessive cooling can harm the embryo and reduce hatch rates.
  • Best practices for cooling periods in incubation: To maximize the benefits of cooling periods, follow these guidelines:
    • Limit cooling periods to once a day.
    • Keep the duration between 10-20 minutes.
    • Monitor the temperature and humidity closely to ensure they remain within the appropriate range.

Emergency Measures to Preserve Egg Viability

In case of unexpected heat loss, take the following emergency measures to protect the fertilized eggs:

  1. Temporary heat sources: Utilize chemical heat packs or insulated containers to provide short-term heat while you address the underlying issue.
  2. Maintaining proper humidity: Use a spray bottle to mist the eggs, or add a damp cloth to the incubator to help maintain appropriate humidity levels.
  3. Monitoring temperature and humidity: Use a digital thermometer and hygrometer to closely monitor temperature and humidity, making adjustments as needed.
  4. Seeking professional assistance: If you’re unsure how to handle the situation, consult with a veterinarian or experienced poultry breeder for guidance.

Preventing Heat Loss in Fertilized Eggs

To minimize the risk of heat loss, follow these best practices:

  • Ensuring proper incubator function: Regularly inspect your incubator to ensure it’s functioning correctly, and address any issues promptly.
  • Insulating the incubation area: Make sure your incubator is well-insulated to help retain heat.
  • Utilizing backup power sources: Consider investing in a backup power source, such as a generator or battery backup, to maintain consistent heat in case of power outages.
  • Regularly monitoring temperature and humidity: Check temperature and humidity levels throughout the day and make adjustments as needed to maintain optimal conditions.


In summary, fertilized eggs require consistent heat to ensure successful development and hatching. The ability of an egg to survive without heat depends on the stage of embryo development, temperature fluctuations, humidity levels, and eggshell quality. Cooling periods can be beneficial if managed properly, but extended exposure to low temperatures can be detrimental to the embryo. Taking preventive measures and being prepared for emergencies can help increase hatch rates and ensure the health of the developing chicks.


  • Nathan Collins

    Having spent years working in the landscaping industry, Nathan Collins has cultivated a wealth of knowledge about the natural world. He is committed to helping others appreciate the beauty in their backyards, whether it's through identifying rare rocks and minerals or crafting the perfect landscape.

Leave a Reply