Low hatch rate: diagnose before starting again

A low hatch rate does not automatically mean a bad incubator. Breeder fertility, storage, transport, temperature, humidity, turning, ventilation and hygiene can produce similar symptoms.

A useful diagnosis starts with two numbers: eggs set and eggs confirmed fertile.

Calculate two different rates

Suppose 100 eggs are set, 80 are fertile and 60 chicks hatch:

hatch rate from eggs set = 60 ÷ 100 = 60%;
hatch rate from fertile eggs = 60 ÷ 80 = 75%.

The first rate describes the overall economic result. The second is more useful for evaluating storage and incubator management. Without candling or reliable examination, the two problems remain mixed together.

Diagnose by symptom

Main symptom	Causes to check first	Next check
Many clear eggs	Fertility, flock age, long storage, rough transport	Candle around day 7 and compare suppliers or batches
Blood rings or early deaths	Storage, contamination, temperature shock, unstable temperature, handling	Check dates, hygiene, pre-warming and day 1–7 records
Embryos die in mid-cycle	Temperature, turning, ventilation, breeder nutrition	Inspect turning mechanism and differences across tray zones
Fully formed chicks with no pip	Temperature/humidity, ventilation, malposition, turning stopped incorrectly	Review timing and air-cell development
Pipped but did not hatch	Unsuitable humidity, poor ventilation, weak chicks, repeated opening	Review the final three days and every lid opening
Very early hatch	Average temperature too high	Compare the sensor with a reliable instrument
Very late hatch	Average temperature too low, eggs stored too long	Check calibration and egg age

One symptom can have several causes. Do not buy a replacement part based only on one table row.

Step 1: separate fertility from mortality

Candle around day 7 in a dark room, with clean hands and without leaving eggs out for long. A clear egg may be infertile or may have suffered a very early death; experience improves the distinction.

Carefully remove eggs that leak, smell bad or show obvious contamination. Do not break a swollen or suspicious egg near the incubator.

Step 2: reconstruct the timeline

Collect the following information:

laying or receipt date and storage duration;
alarm times and values;
morning and evening temperature and humidity;
actual turning frequency;
power outages and backup duration;
day and time of first pip and first hatch.

A narrow but low hatch does not point to exactly the same causes as a hatch spread over more than two days.

Step 3: check the empty machine

After the cycle and cleaning, run the incubator empty. Compare its display with a reliable instrument and measure several tray positions. Inspect the fan, air inlets, turning and recovery after a simulated outage if the manufacturer allows that test.

Never work on a live mains circuit. A sticking relay, hot cable or damaged insulation must be checked by a competent person.

Step 4: examine the egg batch

Record the source, breeder age if known, cleanliness, irregular size, cracks and transport time. Avoid comparing two cycles if both the machine and the egg source changed at the same time.

For the next test, use a uniform, traceable batch where possible and change only a small number of clearly documented factors.

After hatch: examine cautiously

Examining unhatched eggs can provide clues, but it exposes the operator to bacteria and requires experience. Wear gloves, work away from chicks, clean the area and dispose of waste according to local practice. Never eat incubated eggs.

If you suspect breeder disease, repeated deformities or unusual mortality, consult a local veterinarian or poultry technician.

Plan the next cycle

Calibrate measurements before loading eggs.
Use one traceable batch.
Keep records twice daily.
Candle on consistent dates.
Change only one main factor.
Compare hatch from eggs set and hatch from fertile eggs.

Start by checking the temperature and humidity settings. If the cycle included an outage, also use the power-cut procedure.