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Determining the Nitrogen Budget and Total Ammoniacal Nitrogen Emissions from Commercial Broilers Grown in Environmental Chambers

L. Mitran^*, J. M. Harter-Dennis^*,1 and J. J. Meisinger

^* University of Maryland Eastern Shore, Department of Agriculture, Princess Anne 21853; and USDA-ARS, Beltsville, MD 20705

Correspondence: ¹ Corresponding author: jmharterdennis{at}umes.edu

One of the undesirable by-products of raising commercial broilers in confinement is the production and release of NH₃ into the environment. Ammonia negatively affects flock performance, reduces air quality, increases N deposition into neighboring ecosystems, and reduces plant-available litter N. Animal agriculture is currently under pressure to reduce NH₃ emissions. Understanding the fate of N inputs and outputs from commercial broiler operations is important for increasing flock N efficiency and reducing gaseous N emissions. A total direct-measurement N balance trial was conducted on broilers from 0 to 42 d of age with all N inputs and outputs measured. The N inputs included feed and chick N, whereas outputs included broiler N retention, total ammoniacal N (TAN) emissions, mortality N, and litter N accumulation. The major N input was feed N, accounting for 99% of total inputs. After 42 d, the percentage of N input recovered was as follows: 67 ±2% in live broilers, 26 ±2% accumulated in the litter, and 13 ±0.4% in TAN emissions. The average difference between the measured N inputs and outputs was 5 ±3%, indicating a good N balance. The period from 0 to 21 d of age accounted for 23% of the flock total TAN emissions. The remaining 77% of TAN loss occurred from 22 to 42 d of age, most likely due to greater N excretions in the feces and a rise in litter pH and moisture resulting in greater NH₃ production. Daily TAN emissions ranged from 0.13 to 0.78 g of TAN per bird, with a 0 to 42 d mean of 0.37 g of TAN per bird. Total TAN emissions over 42 d averaged 15.3 ±0.5 g of TAN per bird, which is consistent with other literature values and the high N recovery in the broilers. The TAN emission from a complete broiler cycle, including the emissions for a week interval between flocks, was 17.5 ±0.5 g of TAN per bird. These results support the view that management practices leading to high broiler N recovery are consistent with lower TAN emissions.

Key Words: ammonia emission • nitrogen budget • broiler • ammoniacal nitrogen