From day 18 the eggs should not be turned

The way to regulate the system so that the conditions are the most suitable is:

Temperature:

It is reduced to 35.5°C-36°C, since in the last days, the egg offsets more heat.

Ventilation:

It is positive that the CO2 concentration increases a 3 per 1000 (in the incubator) until 5-6 by 1000 from day 19 to day 21, because this way it stimulates the onset of air breathing by the chick.

Ventilation should be limited to slowly increase the rate of CO₂.

Humidity:

It does increase the relative humidity to 70%.

Once the hatching is started, the humidity increases to 85% (this facilitates the breaking of the shell). Eggs can be sprayed with warm water, from day 19 until hatching thereof, to increase the humidity to facilitate breaking of the shell by the chicks.

When the hatching has been completed, the relative humidity decreases sharply to 40% by increasing ventilation (which favors chick drying).

An excellent method to determine the correct humidity is to watch the egss to the light at different stages of incubation. The size of the air chamber after 7, 14, and 18 days of incubation for a chicken egg is shown in the chart below. The necessary adjustments for the moisture can be made as a result of the inspection of the egg to the light. The egg weight should decrease by about 12% during incubation if a good rate of birthdates is expected.

The most critical period is when there is a change in the breath of the embryo, which goes from chorioallantoic to pulmonary. It is the moment when 50% of all deaths are produced regardless of whether the results would have been bad or successful. This period lasts about 6 hours, if it does not occur, the embryonic death occurs. The causes are varied from occurring problems in transferring the eggs to the hatcher, incomplete disinfection, lack of oxygen or moisture, wrong temperature, wrong position or early or delayed removal of the chicks in the incubator.

Early initial mortality - represents at least 60% of the total mortality; there are several factors or causes involved in the process. Before detailing management practices on the incubated egg and during the incubation process, two concepts should be defined, such as: fertility and hatchability, which are often confused. Both parameters provide great information on the performance of the reproducters.

Fertility refers to the number of fertilized eggs in relation to the number of eggs laid in the incubator, once the clear eggs are discarded by looking to the the light at day 14 of incubation. That is, fertility shows the union of sperm and egg.

From what has been mentioned, it is deduced that a poor fertility can only be attributed to the reproducers.

By contrast, hatchability refers to the success of the incubation process or what is the same, the capacity of the egg to hatch, producing a live chicken.