February 13, 2017
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.
Example of climate requirements for setter and hatcher inlet air
*Above 70% relative humidity increases the risk of fungal growth
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:
Outside air of 10°C and 75% relative humidity (RH): This air contains only 5.7g water per kilogram of air, which means that both heating and humidification are required to bring it within climate specifications. Just heating to 21°C is not enough, because subsequently adding water by spraying or fogging causes the temperature to drop again with evaporation. The most energy-efficient option within the climate specifications is 21°C/53% RH (= 8.2 g water per kilogram), and for that, the outside air should first be heated to 27.6°C. This requires 17.8 kJ/kg of air.
Outside air of 30°C and 75% RH: Although RH is the same as in the previous example, this air contains 20.2 g more water per kilogram of air. Cooling this air to 25.1°C will result in 100% RH, which equals the condensation or dew point. However, water content is still the original 20.2 g/kg of air; further cooling to 19°C is required to achieve the maximum specification of 13.8 g water per kilogram of air. This air, however, is still too cold and should be heated up to at least 21°C. At that temperature, though, RH is 88% — far higher than the maximum specification of 70%. To reach that RH, heating to approximately 25°C is required. The energy required for cooling from 30°C to 19°C is 27.6 kJ/kg of air, and heating to 25°C takes another 6.1 kJ/kg of air.
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.
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