<i>Particulate Matter Suppression and Heat Stress Relief in a Cage-free Hen House</i>

Compared to conventional cage production system, cage-free (CF) hen housing offers hens more space and opportunities to exercise their natural behaviors (e.g., perching, dust bathing, and foraging). However, CF housing poses many inherent environmental challenges, among which are high levels of particulate matter (PM). Spraying liquid agent (e.g., 125 mL m-2 per cm litter depth) has been shown to effectively mitigate the generation of PM by 60%-70% from CF henhouse litter in our previous lab-scale tests. The objectives of this study were to verify the lab-study findings of PM reduction with liquid spray on a commercial CF farm and to evaluate the cooling effect of liquid spray on hens in hot weather. This study was conducted with a commercial aviary CF house (50,000 laying hens) in Iowa during winter of 2017-2018 and summer of 2018. A water sprinkling system was installed in half of the experimental henhouse in the length direction (treatment section), whereas the other half of the henhouse served as the control. Results show that the PM emission was reduced by 37%-51%. Adjusting spray dosage according to litter depth is necessary for maintaining a certain reduction efficiency. Litter moisture content of the treatment sections was 9%-14% higher relative to the control, but NH3 concentrations in treatment and control were similar. For the summer cooling, sprinkled hens had up to 7 oC lower body surface temperature than non-sprinkled one immediately after a 20-sec or 30 mL m-2 water spray. The sprinkled hens were still 5 oC cooler than the non-sprinkled ones 3 min after spray. The cooling effect for some birds lasted for about 10 min, but most would dry out soon under the testing conditions (temperature of 35 oC and relative humidity of 32%).