calendar icon 3 December 2018
clock icon 3 minute read

Ammonia is the most common poison in the pig's environment. The concentrations of the various gases found in piggeries are expressed as parts per million (ppm). Generally ammonia levels are less than 5ppm in well run pig houses. The human respiratory tract can detect levels at around 10ppm. Levels of 50 to 100ppm affect performance, particularly daily gain which may be reduced by up to 10% during prolonged periods of exposure. At levels of 50ppm and above the clearance of bacteria from the lungs is also impaired and therefore the animal is more prone to respiratory disease.

Clinical signs

These include increased coughing and respiratory rates, irritation of the mucosa lining the respiratory tract and an increased incidence of pneumonia. Pigs are restless, uncomfortable and may show increased levels of vice, such as tail biting, ear biting and flank chewing.


This is based on the assessment of air quality by the pig person and observed effects on the pig. Ammonia levels can be measured easily using glass sampling tubes. These are thin glass tubes containing a chemical to which syringes are attached. By drawing air through the chemical, a colour change takes place which indicates the ppm of the gas being tested for.


  • Increase ventilation rates.

Management control and prevention

  • Where levels reach above 30-50ppm ventilation must be improved and other measures taken.
  • Increase the drainage of urine from the house and remove solid faeces daily. If a slurry system is used, remove slurry regularly and prevent a crust developing on the surface. Proprietary products that include an extract of the yucca plant are effective in reducing ammonia production in slurry.
  • When designing houses keep the surface area and depth of the slurry to a minimum.
  • Slurry systems that are flushed every twenty minutes reduce ammonia levels.
  • Do not store slurry under slats. Empty frequently to holding areas. Make alterations to the diet to reduce nitrogen excretion.

Emily Houghton

Editor, The Pig Site

Emily Houghton is a Zoology graduate from Cardiff University and was the editor of The Pig Site from October 2017 to May 2020. Emily has worked in livestock husbandry, and has written, conducted and assisted with research projects regarding the synthesis of welfare and productivity of free-range food species.

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