Ammonia Emissions of Laying Hens as Affected by Stocking Density and Manure Accumulation Time

International audience

English. Different stocking densities (SDs) or space allocations are being practiced in commercial laying-hen operations as an attempt to improve hen welfare. Information concerning the impact of SD on accumulated manure properties (e.g., moisture content) and thus ammonia (NH 3 ) emissions is limited in the literature. Bird SD affects the amount of manure per unit of accumulated manure surface area, which may affect the NH 3 emission from the accumulated manure. A lab-scale study was conducted that resembled the conditions of manure-belt laying-hen houses for, with the objectives of (a) determining NH 3 emission rate (ER) of W36 laying hens housed under different SDs; (b) measuring the NH 3 emissions from laying hen manure during 7-d manure accumulation time (MAT); and (c) delineating the dynamics of feed disappearance, manure production and NH 3 ER during dark and light periods. Two different SDs were evaluated, 413 vs. 620 cm 2 /hen (64 vs. 96 in 2 /hen), designated as HD and LD, respectively. Ammonia ER was expressed in the units of NH 3 emission per bird, per kg of feed nitrogen (N) disappearance, per kg of as-is and dry manure, per kg egg output, per m 2 of projected manure surface area (PMA), and per animal unit (AU, 500 kg BW). Results show that SD effect on NH 3 ER is more pronounced for MAT ≥ 3d, where led to higher ER. Specifically, NH 3 emissions from the 3 rd to 7 th d MAT ranged from 41 to 307 mg/hen-d for HD and from 29 to 188 mg/hen-d for LD. This outcome supports the current industry practice of removing manure at 1-to 3-d MAT for the manure-belt house systems. Daily NH 3 ER increases exponentially with MAT (P&lt;0.0001). The results also showed that hourly NH 3 ER during the night or dark period was as high as the hourly emissions during the daytime or light period.</p></div>