Successful egg incubation depends on five things working together: fertile eggs, correct storage, stable temperature, controlled moisture loss, and adequate turning and ventilation. A perfect-looking incubator cannot compensate for infertile eggs or poor storage, while good eggs can still fail when the machine runs too hot, too cold or without reliable power.
This guide focuses on chicken eggs and the practical conditions faced by Nigerian and African poultry keepers. It explains how to prepare the incubator, manage the 21-day cycle, candle eggs, handle power interruptions and investigate a poor hatch without guessing.
Chicken egg incubation at a glance
| Stage | Temperature | Humidity approach | Main action |
|---|---|---|---|
| Before setting | Test the empty machine | Confirm the sensor works | Stabilise the incubator and prepare backup power |
| Days 1–7 | Follow the setting for your incubator type | Maintain steady moisture loss | Turn eggs and record readings |
| Days 7–14 | Keep conditions stable | Check air-cell development | Candle and remove leaking or clearly failed eggs |
| Days 15–17 | Avoid unnecessary adjustment | Continue monitoring | Prepare the hatcher or lockdown area |
| Day 18 | Maintain the manufacturer’s hatch setting | Increase humidity for hatch | Stop turning and begin lockdown |
| Days 19–21 | Avoid temperature spikes | Do not block ventilation to raise humidity | Keep the incubator closed while chicks hatch |
Important: these are management stages, not a substitute for the manual supplied with your incubator. Sensor position, fan design, room temperature and altitude affect the reading inside a machine.
Forced-air and still-air incubators are not the same
A forced-air incubator uses a fan to circulate warm air. A still-air incubator does not. Because heat forms layers inside a still-air machine, its temperature is measured at the top of the eggs and is normally set higher than a fan-forced unit.
- Forced-air incubator: commonly operated around 99.5–100°F (about 37.5–37.8°C).
- Still-air incubator: commonly operated around 102°F (about 38.9°C), measured at the top of the eggs.
These figures are starting references. Use the manufacturer’s instructions for the exact machine and verify the thermometer before setting valuable eggs. Mississippi State University Extension explains how temperature, humidity, ventilation and turning interact during artificial incubation.
Prepare the incubator before setting eggs
Run the empty incubator for at least 24 hours before loading it. This reveals unstable thermostats, hot spots, poor airflow and inaccurate sensors before embryos are at risk.
- Clean and dry the machine according to the manufacturer’s instructions.
- Place it in a secure room away from direct sunlight, rain, cooking heat and strong draughts.
- Check the thermometer and hygrometer against a reliable reference instrument.
- Confirm that the fan, heater, vents and automatic turner work.
- Mark manual-turning eggs with a pencil, not a marker that may contain solvents.
- Prepare a notebook or spreadsheet for morning and evening readings.
- Test the generator, inverter, battery or solar backup before the eggs arrive.
Do not rely on the display alone. A cheap sensor can be wrong by enough to damage an entire hatch. Place a verified thermometer where the embryos are developing, not beside the heater or against the incubator wall.
Choose suitable hatching eggs
Only fertilised eggs from healthy breeding birds can produce chicks. A fresh table egg from a flock without an active rooster will not become fertile because it is placed in an incubator.
Select normal-shaped eggs with intact shells. Reject cracked, leaking, excessively dirty, very small, unusually large or badly misshapen eggs. Double-yolk eggs are poor hatching candidates. Collect hatching eggs frequently so they are not exposed for long periods to heat, rain, manure or direct sunlight.
Do not scrub eggs or wash them in cold, dirty water. Washing can move contamination through shell pores when it is done incorrectly. Commercial hatcheries use controlled sanitation systems; a small farmer should begin with clean nest boxes and clean eggs rather than trying to rescue heavily soiled eggs.
Store fertile eggs correctly
Hatchability normally declines as storage length increases. For a small farm, aim to set eggs within seven days where possible. Store them in a clean, cool place with the broad end up and the pointed end down. Do not store hatching eggs in a normal household refrigerator.
Mississippi State University Extension’s hatch-failure guide recommends controlled cool storage and setting within seven days where possible. If eggs must be stored longer, follow breeder or hatchery guidance for turning and storage management.
Before setting, allow cool eggs to warm gradually to room temperature. Placing cold eggs directly into a warm, humid incubator can cause condensation on the shell, creating a route for contamination.
The 21-day chicken egg incubation schedule
Days 1–6: establish stability
Set eggs broad end up in vertical trays or on their sides in a horizontal machine. Start the turning system and check that eggs move through the intended angle. Record temperature and humidity at least morning and evening. Do not keep changing the thermostat in response to every brief fluctuation; investigate persistent drift.
Days 7–10: first candling
Candle a small group at a time in a dark room. A developing light-coloured egg normally shows blood vessels and a dark embryo. A completely clear egg may be infertile, but a very early embryo death can look similar. A blood ring suggests early embryo death.
Remove eggs that are leaking, cracked, smelling bad or clearly contaminated. Handle uncertain eggs cautiously and recheck them later rather than discarding every difficult-to-read dark-shelled egg.
Days 11–17: monitor development
Continue turning and maintain ventilation. As embryos grow, they produce more heat and consume more oxygen. Large or fully loaded incubators may develop hot zones even when the control panel looks normal. Check readings in more than one location if the machine has a history of uneven hatches.
A second candling around day 14 can show continued development and air-cell growth. Humidity is not simply a number to copy from another farmer. Its purpose is to control moisture loss from the egg. The incubator manual, air-cell development and—where practical—measured egg-weight loss provide better guidance than guesswork. Aviagen’s technical guidance explains the relationship between incubator humidity, egg weight loss, hatchability and chick quality.
Day 18: lockdown
For chicken eggs, stop turning at about day 18. Remove the turning tray if the machine requires it, place eggs in the hatching position, increase humidity according to the machine instructions and make sure the hatching surface is clean and non-slip.
Do not close ventilation openings to raise humidity. Oxygen demand is highest near hatch. Mississippi State University Extension warns that reducing ventilation at hatch can suffocate chicks. Raise humidity through the incubator’s water system or approved surface area, not by blocking fresh air.
Days 19–21: hatching
Keep the incubator closed as much as possible. Opening it repeatedly can cause a rapid humidity drop and dry membranes around pipped chicks. A chick may take many hours between the first external pip and leaving the shell.
Do not pull a chick from the shell simply because hatching appears slow. Premature assistance can tear active blood vessels or expose an unabsorbed yolk sac. Investigate only when there is a clear welfare problem and you understand the stage of hatch. One slow chick does not justify disturbing every egg.
How often should eggs be turned?
When turning manually, turn chicken eggs at least three times daily. Five turns can provide better distribution when it is practical. Use an odd number so eggs do not remain on the same side during the longest overnight period. Wash and dry your hands before handling eggs, work gently and close the incubator promptly.
Stop turning during the final three days before the expected hatch. For chickens this is normally day 18. Other poultry species have different incubation periods, so their stopping dates differ.
How to manage humidity without guessing
Relative humidity affects how quickly water leaves the egg. Too much moisture throughout incubation can leave an air cell that is too small. Too little can cause excessive moisture loss and make hatching difficult. The correct setting depends on incubator design, local air conditions, egg size and shell characteristics.
- Follow the incubator manufacturer’s starting recommendation.
- Use a verified hygrometer rather than trusting an untested display.
- Observe air-cell development during candling.
- Where possible, weigh a representative group of eggs at setting and during incubation.
- Change the exposed water surface or the machine setting gradually.
- Do not add vinegar, disinfectant, perfume, medicine or other unapproved substances to incubator water.
What to do during a power failure
Power interruption is a major planning issue for Nigerian hatcheries and small farms. Research on incubation energy systems in Nigeria identifies unreliable grid power, temperature fluctuation and operating cost as constraints. The practical response is preparation, not panic.
- Record the time the power failed.
- Keep the incubator closed during a short interruption.
- Do not wrap or cover vents in a way that stops airflow, especially late in incubation.
- Start the tested generator, inverter, battery or solar backup.
- When power returns, restore the normal setting. Do not overheat the machine to “make up” for lost heat.
- Record the lowest temperature observed and the duration of the interruption.
- Continue candling and allow for the possibility of a later or wider hatch window.
The effect depends on embryo age, outage length, room temperature, incubator insulation and how quickly conditions are restored. A single outage does not automatically mean the hatch is lost, but repeated temperature instability can reduce hatchability and chick quality.
Why incubated eggs fail to hatch
| What you observe | What to investigate |
|---|---|
| Many clear eggs | Male fertility, mating ratio, breeder age, egg storage, handling and very early embryo death |
| Blood rings or early death | Temperature spikes, contamination, rough handling, poor storage or breeder-flock problems |
| Hatch starts too early | Incubator running consistently too warm or hot spots |
| Hatch starts late | Incubator running consistently too cool, old eggs or repeated cooling |
| Wide hatch window | Uneven temperature, mixed egg age, inconsistent storage or different setting times |
| Chicks pip but do not emerge | Humidity, ventilation, malposition, weak embryos or temperature problems |
| Bad smell or leaking egg | Bacterial contamination; remove safely and clean affected surfaces |
| Weak chicks or poorly healed navels | Temperature, sanitation, hatch timing, breeder nutrition or post-hatch holding conditions |
These signs are investigation prompts, not proof of one cause. Diagnose a failed hatch from the complete record: breeder flock, egg age, storage, temperature, humidity, turning, ventilation, power interruptions and what was found during candling or break-out examination.
Calculate fertility and hatchability correctly
Apparent fertility (%) = eggs showing development ÷ eggs set × 100.
Hatchability of eggs set (%) = chicks hatched ÷ eggs set × 100.
Hatch of fertile eggs (%) = chicks hatched ÷ fertile eggs × 100.
Example: if 100 eggs are set, 85 show development and 70 chicks hatch, hatchability of eggs set is 70%, while hatch of fertile eggs is 82.4%. The two figures answer different questions. Candling alone may not always separate true infertility from death at a very early stage, so describe the result as apparent fertility unless a proper break-out assessment is performed.
Incubation periods for other poultry
| Bird | Approximate incubation period | Management note |
|---|---|---|
| Chicken | 21 days | Stop turning around day 18 |
| Turkey | 28 days | Use turkey-specific hatch guidance |
| Most domestic ducks | About 28 days | Muscovy ducks take longer |
| Japanese quail | About 17–18 days | Use quail-specific trays and settings |
| Goose | Often about 28–35 days | Species and breed differences matter |
Do not incubate different species together merely because they fit inside the same machine. Incubation length, egg size, turning, moisture loss and hatch dates can conflict. Consult species-specific technical guidance and the incubator manufacturer.
After the chicks hatch
Leave newly hatched chicks until they are dry and active, then transfer them to a prepared brooder. Do not leave chicks for an unnecessarily long period while waiting for eggs that have clearly failed. The brooder must already have a stable heat source, clean water, chick feed, dry litter and enough space.
Use the PA chick brooding guide to prepare the brooder before hatch day. For unexplained losses after transfer, review the early chick mortality guide. Clean and disinfect the incubator after removing hatch debris, following the manufacturer’s instructions and the principles in the Poultry Affairs biosecurity guide.
Frequently asked questions
Can I tell whether a fresh egg is fertile before incubation?
Not reliably by candling. Development becomes visible only after incubation begins. Fertility depends on the breeder flock, and early embryo death can later resemble infertility.
Should I wash dirty hatching eggs?
Start with clean eggs from clean nests. Incorrect washing can damage the cuticle or move contamination through shell pores. Do not use heavily soiled eggs for a small-farm hatch.
Can eggs hatch after day 21?
Yes. A cool-running incubator, old eggs or power interruptions can delay hatch. A late hatch should trigger an equipment and record review rather than become the normal target.
Can I open the incubator during lockdown?
Avoid opening it unnecessarily. Opening can release heat and humidity, especially after chicks begin pipping. Intervene only for a clear management or welfare reason.
Does a low hatch always mean the incubator is faulty?
No. Fertility, breeder health and nutrition, egg age, storage, contamination, handling and incubation management can all reduce the result. Use records and a structured break-out review.
Final incubation checklist
- Use clean, normally shaped fertile eggs from a healthy breeder flock.
- Set fresh eggs and store them correctly before incubation.
- Test the incubator and backup power before loading.
- Use the correct temperature for the incubator type.
- Turn consistently and stop at the correct time.
- Manage humidity through evidence, not additives or guesswork.
- Keep ventilation open, especially near hatch.
- Record temperature, humidity, turning, candling and outages.
- Calculate both hatchability of eggs set and hatch of fertile eggs.
- Prepare the brooder before the first chick emerges.
Good incubation is controlled observation. Use one reliable procedure, record what happened and investigate patterns across several hatches. That approach improves results more safely than changing settings or adding unverified substances after every disappointing batch.
