Ammonia Emissions from USA Broiler Chicken Barns Managed with New Bedding, Built-up Litter, or Acid-Treated Litter

Poultry producers in the United States have attempted to maintain barn aerial ammonia (NH3) levels below 25 ppm to improve air quality, and more recently to decrease aerial emissions to the atmosphere. Our objective was to investigate the influence of litter management strategies on NH3 emissions from commercial broiler barns employing new bedding, acid-treated built-up litter (sodium bisulphate), or untreated built-up litter (normal practice). Nearly 400 barn-days of NH3 emissions data were collected from 12 broiler barns on four farms monitored in 48-hour episodes over one year. On each study farm, the barns were paired for repetition of conditions. Emission was calculated as the product of gas concentration of the exhaust air and barn ventilation rate. Use of new bedding for every flock led to consistently lower NH3 emission (averaging 0.35 g NH3/(bird d)) at day 21 of the 42-day flock grow-outs, followed by flocks raised on the annual cleanout with new bedding (0.52 g NH3/(bird d)). Built-up litter without any treatment had the highest emission (0.73 g NH3/(bird d)), followed by the built-up litter with acid treatment (0.63 g NH3/(bird d)). One study site was managed with two barns using litter treatment and two identical barns with untreated, built-up litter for a side-by-side comparison of results under field conditions. Ammonia emissions from treated built-up litter barns were similar to those from untreated built-up litter barns, however, the temporal pattern of emissions provided evidence that ammonia held in the acid-treated litter at the beginning of the flock was released during the latter period of the flock cycle.