Ammonia emissions in poultry houses and microbial nitrification as a promising reduction strategy

Abstract

High ammonia (NH3) levels (>25 ppm) in poultry houses reduce the body weight gain, feed conversion, survival ability, carcass conviction rate, and immune system of birds. High NH3 levels can also cause pain, eye-inflammation, and increased oxidative stress. The volatility rate of NH3 in poultry litter depends on the pH, humidity, ventilation rate, air velocity, manure nitrogen (N) content, and temperature. The litter's pH is a major factor regulating the volatilization of NH3because it specifies the volatile ammonium (NH4+)/NH3 ratio between their ionic and nonvolatile forms. High NH3 levels damage birds' respiratory systems' mucous membranes, thereby increasing their susceptibility to respiratory infections, particularly to Escherichia coli infection. In this review, the existing knowledge on soil-nitrifying bacteria and NH3 nitrification approaches for advancing poultry manure microbial nitrification and environmental implications of using various NH3 emission control techniques were summarized. Although few studies have focused on reducing NH3 volatilization by nitrification, nitrification is deemed a sustainable approach for reducing N excretions and controlling NH3 emissions in poultry houses. However, further studies are required to determine the most suitable soil nitrification bacteria to increase microbial nitrification