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العربية (Arabic)
For many years, raised CO2 levels at the end of the incubation period were thought to be harmful for the developing bird embryo. This is a myth that couldn’t be further from the truth. Both from science and research under commercial conditions, it is made clear that CO2 even has a positive impact on hatchability and chick quality.
By Bruno Machado & Eduardo Romanini
Incubation Specialists Research & Development
Petersime Incubators and Hatcheries
Under natural circumstances, the level of CO2 measured in the micro-environment under mother hen reaches 0.4% or 4,000 ppm at least, and often more. This represents ten times the normal level of CO2 in the outside air. In fact, when sitting on the eggs, mother hen cuts off the airstream around the eggs to create a protected environment so that embryos can develop in the best possible conditions.
Eager to better understand this process, Petersime set out to determine the optimal CO2 levels during hatching and the correct moment to raise them.
Three essential levels
It’s long been known that in hatcheries, healthy chicks come from mastering and controlling three essential levels, in this order:
1 Temperature: the most important environmental parameter, as a slight increase or decrease can severely affect embryonic development, hatchability and post-hatch performance.
2 CO2 and O2 levels: affect the development of the embryo’s cardiovascular system, and thus its respiration.
3 Humidity level of the air surrounding the eggs: determines the rate at which the eggs lose water and, as a result, lose weight.
Fundamental changes from day 18 on
Many studies have confirmed that dramatic changes occur to the chick, both physically and physiologically, from around day 18 onwards of the incubation period. The most relevant change occurs when internal pipping starts; that’s when the internal eggshell membrane is perforated giving access to the air chamber. This is then followed by external pipping and continues until the chick fully emerges from the shell. The whole process is the transition from fluid to dry.
Figure 1 Respiratory evolution of a chick
In essence, the O2 and CO2 levels in the egg’s air cell change as the embryo begins to adopt convective gas exchange by inflating its lungs – in other words, breathing! Previous studies indicate that the O2 level decreases to approximately 14.2%, while the CO2 concentration rises to about 5.6%. Some might consider th...
