Hatching eggs successfully is both an art and a science. Many poultry farmers and backyard hatchers eagerly wait for their chicks to emerge from their shells, only to be disappointed when some fully developed embryos fail to hatch.
Understanding why this happens is crucial for improving hatch rates and ensuring a healthy batch of chicks. This guide dives deep into the various reasons eggs develop but don’t hatch and provides practical solutions to prevent this issue in the future.
Understanding Egg Incubation and the Hatching Process
To troubleshoot unhatched eggs, it’s essential to first understand the incubation process. A fertilized egg develops in a highly controlled environment inside an incubator or under a broody hen. The entire process takes approximately 21 days and can be broken down into the following stages:
- Days 1-7: The embryo begins forming, and blood vessels start developing.
- Days 8-14: The embryo continues growing, with the beak, eyes, and legs becoming distinguishable.
- Days 15-18: The chick moves into position, absorbing the yolk for energy.
- Days 19-21: The chick should pip (break through the shell), then zip (fully emerge).
When a chick doesn’t hatch after reaching the later stages of development, it’s likely due to issues in one of the following areas.
Top Reasons Eggs Develop But Don’t Hatch
1. Incorrect Temperature Levels
Cause:
- Temperature that is too high or too low can cause developmental abnormalities.
- High temperatures accelerate growth, leading to premature hatching attempts and weak chicks.
- Low temperatures slow development, causing underdeveloped or nonviable chicks.
Prevention & Solution:
✅ Maintain the correct temperature:
- Forced-air incubators: 99.5°F (37.5°C)
- Still-air incubators: 100-101°F (37.7-38.3°C)
✅ Use at least two thermometers to verify accuracy.
✅ Avoid opening the incubator too frequently, as this causes fluctuations.
✅ Have a backup power supply in case of outages.
2. Humidity Imbalances
Cause:
- Low humidity leads to excessive moisture loss, causing chicks to be shrink-wrapped inside the membrane.
- High humidity causes excess moisture retention, making it difficult for chicks to break through the shell.
Prevention & Solution:
✅ Maintain humidity at 45-55% during incubation and 65-75% in the final three days (lockdown).
✅ Use a hygrometer to measure humidity accurately.
✅ Adjust water trays as needed based on air cell size during candling.
3. Poor Egg Quality and Handling
Cause:
- Eggs from unhealthy or stressed hens may have weak embryos.
- Mishandling eggs before incubation can cause hairline cracks, affecting hatchability.
Prevention & Solution:
✅ Collect only fresh, clean eggs from disease-free hens.
✅ Store eggs properly before incubation at 55-65°F (13-18°C) with 75% humidity.
✅ Turn stored eggs daily to prevent yolk adhesion.
✅ Never wash eggs with water before incubation, as it removes the protective bloom.
4. Genetic and Fertility Issues
Cause:
- Poor fertility due to incorrect rooster-to-hen ratio.
- Inbreeding can lead to weak embryos.
- Some breeds have lower hatch rates.
Prevention & Solution:
✅ Maintain a rooster-to-hen ratio of 1:8-10 for optimal fertilization.
✅ Select breeding stock from strong genetic lines.
✅ Candle eggs on Days 7 and 14 to check for fertility and remove non-developing eggs.
5. Inadequate Egg Turning
Cause:
- If eggs aren’t turned regularly, the embryo may stick to the shell membrane, leading to hatching failure.
Prevention & Solution:
✅ Turn eggs 3-5 times daily or use an automatic turner.
✅ Stop turning on Day 18 to let chicks position correctly.
6. Bacterial or Fungal Contamination
Cause:
- Unclean eggs or incubators introduce bacteria like E. coli or Salmonella, causing embryo death.
Prevention & Solution:
✅ Disinfect the incubator before each batch using a mild bleach solution.
✅ Incubate only clean eggs (without washing them).
✅ Ensure proper ventilation to prevent mold growth.
7. Air Cell Damage
Cause:
- If the air cell detaches due to rough handling or improper storage, chicks may struggle to pip.
Prevention & Solution:
✅ Store eggs with the pointed end down.
✅ Allow stored eggs to rest at room temperature for 12-24 hours before incubation.
8. Inadequate Oxygen Supply
Cause:
- Lack of oxygen inside the incubator can lead to weak or dead embryos.
Prevention & Solution:
✅ Keep ventilation holes open in the incubator.
✅ Avoid overcrowding the incubator to allow proper airflow.
9. Late or No Assistance During Hatching
Cause:
- Some chicks may be too weak to hatch but could survive with assistance.
- A chick that pips but doesn’t progress for 24+ hours may need help.
Prevention & Solution:
✅ Only assist if absolutely necessary and ensure no active blood vessels are present.
✅ Carefully remove shell fragments bit by bit, keeping membranes moist.
How to Conduct a Hatch Failure Analysis
If you experience a high percentage of eggs developing but not hatching, perform a hatch failure analysis:
- Candle eggs on Days 7, 14, and 18 to identify abnormalities.
- Break open unhatched eggs (outside the incubator) and check for development stage and causes of death.
- Keep detailed records of temperature, humidity, turning, and egg sources for future improvement.
Final Tips for Improving Hatch Rates
✅ Use a high-quality incubator with digital temperature and humidity control.
✅ Keep detailed records to track hatching trends and make improvements.
✅ Ensure proper ventilation for oxygen exchange during hatching.
✅ Source eggs from strong, disease-free hens to maximize fertility and chick viability.
Conclusion: Maximizing Hatch Success
If your eggs develop but never hatch, it’s likely due to a combination of temperature fluctuations, humidity issues, improper egg handling, or contamination. By following best incubation practices, regularly candling eggs, and maintaining a clean environment, you can significantly improve your hatch rates.
Every failed hatch is a learning experience. By identifying and correcting these issues, you can increase your success rate and enjoy healthy, thriving chicks in every batch.