The main purpose of a poultry house ventilation system is to remove moisture. As temperatures rise and birds drink more, this becomes more pertinent, especially as humidity levels and air temperature are two of the main contributing factors to heat stress.
Getting the best out of a poultry house ventilation system and providing the best environmental conditions for the housed flocks will provide enormous benefits, not only the health and welfare of the birds but also financial performance.
An example for layer flocks
Maintaining relative humidity between 50% and 70% in a house will keep ammonia and CO2 levels within acceptable parameters.
Laying hens at 90% production will consume around 270 litres/1,000 birds per day. In warm weather this will increase however the higher air temperatures will make maintaining relative humidity levels easier.
A 16,000 housed flock will consume circa 4,320 litres. With free range flocks, the hens will drink from puddles and take dew from grass, however their primary consumption will still be from drinker lines in the house. The eggs produced by 1,000 hens will potentially remove 48 litres from the house (as the egg is 76% water).
Therefore, the balance of 3,552 litres needs to be removed from the house each day to maintain existing moisture levels.
Removing 3.5 tonnes of water by ventilation alone is a challenge and this will only maintain the litter in the condition it currently is in, if it is wet, a lot more water will need to be removed.
There are different types of ventilation system, and all sorts of equipment related to each type. The basic principles are simple – ventilation systems need to introduce the correct volume of air in the correct condition to carry the required quantity of water (as vapour) out of the house and as far away as possible.
The amount of water vapour that the air can “carry” is related to its temperature, therefore even cold moist air from outside the house can pick up and remove water from the litter if it is warmed in some way in the house.
For every 12 degrees c increase in air temperature the moisture holding capacity of air doubles.
Maintenance is key
Ventilation systems require constant adjustment to get the best results and the driest litter and litter conditions do vary with prevailing weather conditions.
Most systems are controlled by temperature with operators selecting a desired house temperature and the system being left to achieve this. It’s important to maintain the system correctly with simple checks such as:
- Remove dust from light baffles
- Adjust inlet linkages to ensure inlets are opening as predicted by the system
- When fans are off inlet vents should close right up to 0% opening
- Clean fan blades and make sure all fans are working
- Ensure the temperature sender is in a relevant place in the house
- Check the minimum ventilation is adequate by turning on during the day and making sure that the house stays reasonably fresh and fog free
If the ventilation is not right and the litter is soggy and or capped, the hens will not perform well.