Heating and good ventilation play an important role in managing litter moisture. The ability of air to hold water increases as the temperature of ambient air increases. Dunlop and Stuetz (2015) provided a general rule that states the relative humidity of air halves if the air temperature increases by 10–14 °C, and the relative humidity doubles if the temperature drops by 10–14 °C. At a given temperature, air is saturated (when it reaches maximum water holding capacity). This is also known as the ‘dew point temperature.’
This heating of air can control litter moisture, particularly during winter in southern Australia, when prolonged wet weather occurs. Heating and good ventilation can remove considerable moisture from sheds (Ritz et al., 2017). Dunlop and Stuetz (2015) described the process of how the transfer of water is regulated by the water activity of the litter and the relative humidity of the air above it. If the water activity in the litter is lower than the relative humidity of the air, then the litter will absorb moisture from the air. However, if the situation is reversed, water will transfer from the litter to the air. Thus, one way to ensure that water evaporates from litter is to ensure that the relative humidity of the air at the litter surface is as low as possible.
To enable sufficient water evaporation from litter, ensure the relative humidity of the air at the surface of the litter is kept as low as possible (<60%). Heating can help remove litter moisture, as warmer air holds more moisture. The relative humidity of air roughly halves if the air temperature is increased by 10–14 °C, and the relative humidity doubles if the temperature drops by 10–14 °C.
For ventilation to be effective, Dunlop and Stuetz (2015) suggested that incoming air requires conditioning, so that it has low relative humidity (less than 60%) and can absorb moisture from the litter. They also stated that this can be difficult, as most water collects under feeders and drinkers (via excreta and water loss) where chickens congregate. They suggested strategies to regulate the relative humidity of air at the litter surface and keep the air moving, (e.g. using circulation fans and not excessively using evaporative cooling) that may prevent wet litter.
Effective ventilation, heating and humidity control can also compensate for factors that could cause wet litter (e.g. high moisture in bedding material, water added by excreta, drinker spillage or leaks, condensation). As Dunlop (2017) explained, adding additional dry litter (including repositioning of dry litter that may already be in sheds), or increasing ventilation or heating, can compensate for poor litter water holding capacity. Increasing ventilation, or making it more effective at chicken height, will reduce in-shed humidity and increase evaporation.
Temperature variation can cause chickens to congregate in cooler areas when they are hot or warmer areas when they are cold. This uneven stocking density can cause uneven manure distribution and lead to areas with wet litter. This will indicate that maintenance is required, or ventilation system changes are needed to prevent temperature variation.
