Chapter 8 - Moisture Production and Removal

Broilers eliminate moisture through respiration, evaporation, and fecal evacuation. Broiler size, environmental temperature, housing type, manure handling practice, and watering systems all contribute to apparent moisture production. Published moisture production rates are either from calorimeter (chamber) studies or from whole-house studies; the latter typically have higher values because they include evaporation of water from feces and the drinking water system. Significant differences in moisture production between broilers raised in houses with conventional versus tunnel ventilation have been found. This difference is presumed to be due primarily to changes in water delivery systems that have occurred over the two decades since the data for the conventional housing system were collected.

Moisture balance

Moisture balance occurs when the rate that water vapor produced by broilers, feces, and the drinking system equals the rate that water vapor is expelled by the ventilation system. The ventilation rate needed to achieve the moisture balance is the minimum ventilation rate, usually expressed in cubic feet per minute (CFM).

The recommended values for minimum ventilation rate start at 0.04 CFM per chick for young broilers and increase as broilers grown and their moisture production increases. Broilers reared on fresh litter can withstand short periods of low ventilation because the litter can absorb moisture. However, excess litter moisture will lead to ammonia and disease problems. If a low ventilation rate is used (for example, to save fuel during cold periods), the moisture must be removed later in the production cycle using higher ventilation rates. If broilers are raised on previously used litter, the required minimum ventilation could be as much as nine times that normally recommended to keep ammonia levels within the desired range. For broilers, recent research suggests that today’s young broilers and production practices result in significant higher moisture production than two decades ago. This translates into higher minimum ventilation rates to remove this moisture.