<i>Mitigating Particulate Matter Emissions of a Commercial Cage-free Aviary Hen House</i>

Abstract

Concerns over animal welfare among general public and marketing decisions have led to pledges by a number of U.S. food retailers and restaurants to source only cage-free (CF) eggs in the foreseeable future, e.g., by 2025. Compared to conventional cage production system, 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) and ammonia (NH3). 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 indoor air and litter quality before and after liquid spray. This field verification study was conducted with a commercial aviary CF house (50,000 laying hens, L×W×H = 154 × 21.3 × 3.0 m) in Iowa during winter of 2017-2018. 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. In each trial, the spray dosage (125 mL H2O m-2 per cm litter depth) was adjusted according to the initial litter depth before the spray. A total of three trials were conducted in this study. Results show that the PM concentration was reduced by 37-51% PM in the commercial aviary henhouse. The lower reduction efficiency in the field than the values obtained in the lab tests was partially attributed to the fact that water spray was applied to only the open litter area, and the litter area under the aviary system was not sprayed. 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 than control (i.e., 15.6% vs. 14% for Trial 1, 14.6% vs. 12.2% for Trial 2, and 17.7% vs. 14.9% for Trial 3), but NH3 concentrations in treatment and control were similar during the test.