High summer temperatures result in higher ventilation rates, which should mean drier litter. So why is caked litter often an issue, particularly near the cool cells?
It takes three things to remove moisture from litter – heat, air movement and moderate humidity (40-60%).
Basics of Litter Moisture in Cold Weather
In the winter, it’s fairly easy to understand why caked litter can be relatively common. Though house temperatures may be correct, producers may tend to be conservative with ventilation in an effort to save on fuel costs. Lower ventilation rates result in high house humidity (+70%) which make it difficult to remove moisture from the litter. In addition, lower ventilation rates typically result in a relatively minimal amount of air movement over the litter.
In this situation, we’re missing two of the three factors that help maintain dry litter–moderate humidity and air movement which increases the likelihood of caked litter. The situation can be improved with a circulation fan system that can help generate some air movement across the litter surface, resulting in some level of litter drying.
Understanding Wet Litter in Hot Weather
During hot weather, ventilation rates are primarily driven by house temperature. As temperatures increase, more fans turn on in an effort to remove more heat and keep birds cool with higher air speeds. So higher air speeds mean dry litter throughout the house, right?
1. Evaporative cooling is not in use
2. The level of air movement in the cool cell area was as high as that as in the remainder of the house.
Evaporative Cooling = Moisture
The use of evaporative cooling pad increases the incoming humidity. For every one degree of cooling, humidity will increase by 2.5%. The more we use our evaporative cooling systems, the more humid the air will become.
The use of evaporative cooling pads results in an incoming Rh of between 75 and 85% Rh, though it can be higher when cooling pads are overused. So, though we are bringing in a lot of air, it has a relatively low ability to remove moisture from the litter.
The Importance of Air Speed
Air enters through cool cells (tunnel inlet) relatively slow and does not reach maximum air speed until the end of the pad. Only once air passes the transition zone and into the pipe section of a house does it start to increase and reach target air speed. The litter at the tunnel inlet end as well as the transition zone have slower air moving across it which reduces litter drying. You can often see the litter become noticeable drier 50’ or so past the end of the tunnel opening.
*courtesy of UGA Poultry Science Department
One way to help minimize this issue is by relying on airspeed to cool birds rather than evaporative cooling systems. For example, on market age birds you would turn on all tunnel fans before turning on the cool cell systems. A second way is to delay the use of evaporative cooling pads until house temperature reaches between 82-85°F.
Unless you’re growing birds in a very dry climate, turning cooling systems on at a lower temperature will likely harm you more than help you when it comes to litter quality as well as bird cooling.
Have more ventilation questions? Let us know!