Ideal situation: warm eggs heat cold eggs
16-18
13-15
10-12
7-9
4-6
Multi-stage or single-stage
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In multi-stage systems, the setter trays are divided over the height and width of the machine in a fixed pattern (protocol of incubator manufacturer). In a full incubator, the embryos are nine days old on average. The eggs already in the incubator heat the new eggs. The setpoint of the incubator temperature is a constant value.
There are two, basic methods of incubation: multistage and single-stage. Technological developments, such as automation and climate control have driven upscaling of hatcheries. This prompted a transition from multi-stage incubation to single-stage incubation, which is now the standard practice. In a multi-stage setter, fresh eggs are set at different times, usually at three-day intervals, and fixed climate settings are used. Because the embryos are at different development stages, average settings are assumed. Eggs in a more advanced stage of development heat up newly set eggs and, the other way around, the developed eggs are cooled by the newly set eggs. The advantage of this system is optimal flexibility, but there are never optimal conditions for all the different ages of embryos. There is also a higher risk of contamination, because new eggs are loaded into the setter each time. This carries the risk of cross-contamination between batches. It is also difficult to clean the incubator because it is not emptied each time. But a multi-stage incubator still has to be cleaned and disinfected - preferably every six weeks. In the meantime, noticeable soiling should be removed each time new eggs are set. In a multi-stage hatchery, the eggs are pre-warmed in the setter room (25-27°C/77-81°F) for at least 12 hours. Better controlled pre-warming in the setter is an advantage with single-stage. With a single-stage system, all the eggs are loaded in the setter at the same time and the climate settings are adjusted during the process, based on the development stage of the embryo. This results in better quality day-old chicks. To maintain the embryo temperature at 37.8° (100°F), the set temperature must be slightly higher to start with and slightly lower later on, once the embryos start to produce heat themselves. An advantage of a single-stage system is greater hygiene as the incubator can be properly cleaned and disinfected when it is empty. A disadvantage is that it requires more heating, cooling and ventilation. But the results are better with single-stage, even during the later stages of the chicks’ lives.
13-15
10-12
7-9
4-6
py
16-18
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In practice: formation of hot spots and cold spots
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In practice, the air does not flow in a uniform pattern through the trolleys. The tilted trays slow the airflow, resulting in less optimal transport of heat. Hot spots form at the top in heat producing trolleys and cold spots at the bottom of trolleys with fresh eggs.
Solution: position some trays horizontally
16-18
13-15
10-12
7-9
4-6
1-3
The solution can be to position trays of eggs at a further stage of development horizontally. This will obstruct the airflow less.
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Ha tc he ry S i gnal s
