Carbon monoxide

Carbon monoxide poisoning in swine occurs where faulty gas heaters are used in farrowing houses and ventilation is poor resulting in an increase in stillbirths. Also, the decomposition of faeces, particularly in slatted floored finishing houses produces high levels. 50ppm are not uncommon and suggest inadequate ventilation. Levels of 250ppm however interfere with the uptake of oxygen by the haemoglobin in the pig's blood and similarly in people. Instead of oxyhaemoglobin, carboxyhaemoglobin is formed and the oxygen carrying capacity of the blood is reduced. This markedly increases the number of stillborn piglets. Levels may rise to 50%. Carbon monoxide affects the blood of unborn piglets more quickly than the sow.

Clinical signs

Sows may show dark coloration of the mucous membranes and stillborn piglets are often bright red due to the formation of the carboxyhaemoglobin in the blood. Such levels of carbon monoxide can have a similar effect on people so care should be taken in investigating the housing area.


If gas heaters are used in farrowing houses and a sudden rise in stillbirths occurs, inadequate combustion must immediately be suspected together with poor ventilation. Carbon monoxide levels can be measured using glass sampling tubes.


  • Improve the ventilation immediately, and identify and remove the source of production.
  • Administer oxygen but this may be impractical.