Incubation temperature

Incubation temperature

Based on average values, embryonic development is optimal during the first 18-19 days at an embryo temperature of 37.8°C (100°F). After internal, and then external, pipping, the temperature of the embryos may gradually increase from day 20 to 39°C (102°F). As a rule of thumb, aim for a range in which 95% of the eggs/day-old chicks are no more than 1% below or above the optimal value: 1% of 37.8°C rounds off to 0.4°C. More than 95% of the eggs should therefore be in the range between 37.4-38.2°C. Note: this applies to the Celsius scale. At Fahrenheit you can stick to: between 99.3 and 100.7°F.

Variation inside the incubator

There are always some cold spots and hot spots in an incubator. Cold spots occur in places such as close to the floor, the walls, the point where fresh air reaches the eggs first and around the sprayer or humidifier. Cold spots at the start of the incubation process, and hot spots at the end of the incubation process are places where there is generally little airflow. Some brief variations are not usually an immediate cause for concern. In natural conditions, the hen also occasionally leaves the nest to eat or drink towards the end of the brooding process. Prolonged deviations from optimal conditions may negatively affect embryonic development (and uniformity). Ensure proper incubator maintenance to avoid structural deviations.

Embryo temperature during the incubation process (°F/°C)

Min Optimal Max

Day 1-19 99.3 / 37.4 100.0 / 37.8 100.8 / 38.2 After pipping, day 20 101.5 / 38.6 102.2 / 39.0 102.9 / 39.4 Dry chick 103.1 / 39.5 104.0 / 40.0 104.9 / 40.5

copyright protected

During the maturation stage (approx. from day 16), the embryo can respond slightly to the ambient temperature. If the temperature is too low, the heart rate decreases so the metabolic heat produced by the embryo is not released through the eggshell, but stays ‘inside’ the egg, with the embryo. The opposite also occurs: the embryo responds to ‘feeling’ too hot by increasing its heart rate so that more blood flows along the eggshell. This releases heat to the environment around the egg and allows a higher intake of oxygen. This thermal image shows that the eggs in the centre of the setter tray are much warmer than the eggs at the sides. During incubation, the aim is to create the most uniform possible temperature in the whole incubator. However, the temperature can vary between different parts of the incubator. This is caused by different air velocities and using humidification sprayers.

The most important thing is to maintain a constant, uniform temperature for all the eggs, particularly at the start of incubation. The ventilation is reduced to an absolute minimum (air inlets closed) to ensure the most uniform possible temperature in all the eggs and prevent cold air flowing into the incubator. If the air used to ventilate can be properly conditioned (pre-heated) this is not such a problem.