Hatcheries are found in a variety of climates, from the hot, humid tropics of Southeast Asia to the hot, arid zones of the Middle East or the changeable climates of Central Europe or the U.S. Typically, the external temperature and relative humidity are subject to seasonal changes (e.g., rainy seasons or very cold winters) or even a day and night rhythm.

The challenge is to establish whether outside air is directly suitable for incubation and, if not, how to make it fit for that purpose, according to Pas Reform Academy senior poultry specialist Gerd de Lange.

To a certain extent, setters and hatchers can deal with climatic variations to inlet air, although most incubator manufacturers specify the climate conditions under which their equipment will perform at its best, de Lange said.

Untreated inlet air can be:

* Too cold, which may lead to low temperature uniformity and, especially if occurring early in incubation, an extended hatch window;

* Too warm. During late incubation in the setter and certainly in the hatcher, this will overwork the water cooling system, produce excessive condensation and ultimately wet floors, which will cause eggs close to the floor to become too cold;

* Too dry. Humidification (rotating disc, nozzles) in the incubator may compensate for this but will cause cold spots due to localized evaporation;

* Too humid, which may cause difficulties in achieving sufficient egg weight loss during incubation that can only partially be compensated for by a higher ventilation rate and might ultimately lead to reduced hatchability and poor chick quality.

The Table shows a realistic range of climate specifications for setter and hatcher inlet air.

For hatcheries at sea level, dew point specifications can also be converted to a specific humidity of 8.2-13.8 g water per kilogram of air. There are several Mollier Diagram/psychometric chart-based climate calculation tools available online to help make these calculations, de Lange pointed out.

Conditioning outside air to inlet specifications does not come without a cost, de Lange said, as demonstrated in the following two examples:

De Lange concluded with the following points:

* Consult the incubator manufacturer for setter and hatcher inlet air climate specifications.

* Choose the most energy-efficient (i.e., cheapest) combination of temperature and RH within these specifications after taking outside climate into consideration.

* Ask the incubator manufacturer about available options to further reduce the energy costs for hatchery climate control.

* Do not waste expensive, preconditioned air, avoid over-ventilating incubators and keep the doors of clean air plenums closed as much as possible.