Pre-Incubation will not and cannot improve hatchability, but helps to maintain it over longer periods of time (see Figure 1 below). Therefore it starts making sense using this technique, if eggs are scheduled for a storage period which leads to a noticeable decline in hatchability. The gains made depend on the local conditions of the flock and the storage. Improper cooling after pre-incubation might cause negligible or even negative improvement.
Learning from mother hen
A hen needs approximately 24 hours to produce an egg. Around 30 minutes after an egg is laid the next follicle is ovulated. The follicle falls into the infundibulum where the fertilisation takes place. After that the albumen is added, the egg membranes are formed and the egg shell is composed.
Therefore the eggs arriving at the hatchery contain an embryo representing already 23.5 hours development in the hen’s body. However this developmental stage at point of lay is not optimal for long storage. In nature it would be altered by periodical warming of the eggs during the time the hen sits on the nest to produce the next egg of the clutch. In the hatchery it is possible to achieve similar results by incubating the eggs for 3 to 6 hours during the first storage days. This leads to further development of the germinal disk to a stage containing 60000 – 80000 cells. At this stage the embryo is less susceptible to cell death occurring during the storage period.
How does pre-incubation work?
The aim is to apply 3 to 6 hours of incubation during the first days of storage. These hours mean the time the eggs spend in 100°F/37.8°C incubation temperature. In order to bring the eggs to this temperature the eggs need to be heated-up and they also need to cool down afterwards. The different steps of the total pre-incubation procedure are shown underneath.