Top layer humidification of bedding material of laying hen houses to mitigate dust emissions: effects of water spraying levels on dust, ammonia and odour emissions

Introduction: Spraying small amounts of water on littered floors of aviary housing systems for laying hens could be a (cost) effective mitigation option for fine dust. By the humidification of the top layer of litter, dust generation by animal activity may be decreased. The objective of this study was to determine the effect of spraying different doses of water on the litter of two aviary housing system of laying hens, on the emissions of fine dust, ammonia and odour. Material and Methods: The study was performed in eight climate separated rooms of an experimental poultry farm. Four of the eight rooms were equipped with an aviary system with non-integrated nestboxes, the other four with a portal aviary system, both housing 640 hens.The following treatments were studied in terms of daily water dosing and frequency of daily application : 0 ml/m2, 150 ml/m2 (2 x 75 ml/m2), 300 ml/m2 (2 x 150 ml/m2), 300 ml/m2 (2 x 150 ml/m2) and 600 ml/m2 (2 x 300 ml/m2). Each treatment was replicated once per aviary system. The water film was applied manually using a battery backpack sprayer. The experiment was conducted during 34 days. Mean concentrations, emissions and emission reductions of PM10, PM2,5 ( both gravimetrically) and ammonia were measured on days 19, 26 and 33 of the experimental period. On day 26 the odour concentrations and emissions were determined. Technical results were determined each day (number and quality of eggs; mortality). Behavior (scratching and dust bathing), foot pad condition and plumage condition were observed on days 14, 42 and 49 of the experimental period. Results/Conclusions: Spraying 150 ml/m2 resulted in a reduction of PM10 and PM2.5 emissions of 18% and 44%. An increase of the amount of water sprayed on the litter floor resulted in a proportional increase of reductions. Spraying 300 m/m2 resulted in PM10 and PM2.5 emission reduction of 48% and 59%, while 600 ml/m2 resulted in a reduction of 64% for both PM10 and PM2.5. However spraying 150, 300 and 600 ml/m2 water resulted in an increase of ammonia emission with 21%, 65% and 64%. All reported effects were statistically significant (P 0.05) . Spraying negatively affected litter quality. Due to the worse litter quality smoothening of the plumage and foot pad occurred. The reduced litter quality had no adverse effect on plumage condition and dust bathing behavior of the laying hens. Spraying water on the bedding material had no effect on mortality rate, laying percentage, percentage of second grade eggs and percentage of floor eggs. It is concluded that the investigated principle can be an effective technique to reduce fine dust emissions from aviary houses, if ammonia emission can be reduced. Increasing the frequency of application or the use of water additives could be possible solutions to reduce this negative side effect. Acknowledgements/References: We want to acknowledge the Ministry of Economic Affairs, Agriculture and Innovation of the Netherlands for financing this study.