Ammonia aversion in commercial pigs?

New project planned for 2021.

This study aims to test the averseness of acute exposure to various ammonia concentrations on commercially housed pigs. Due to the high number of pigs under human care and the potential damaging effects, elevated ammonia concentrations may have on the olfactory apparatus of these animals, we believe that further studies are urgently needed to establish, the minimum air quality requirements in commercial pig houses.


Both the scientific community and the general public acknowledge that pigs have a very well-developed sense of smell. It is therefore surprising that conventional pigs often are kept in environments with a huge odour impact (e.g. ammonia). Juvenile Duroc x Landrace crossbreds have an olfactory detection threshold for butanol at 2.09 parts per trillion (Jones et al., 2001) and Götingenminipigs a detection threshold of 0.05 parts per million (ppm) for ethanol and 0.01 ppm for ethyl acetate (Søndergaard et al., 2010). These studies scientifically document the amazing olfactory ability of pigs. It is important that we remember – and acknowledge – the olfactory ability of pigs since 1,5 million pigs are currently housed commercially in Sweden (Jordbruksverket, 2019). If we look towards the EU as a whole, the number of slaughtered pigs exceeded 257 million in 2016 (eurostat, 2017) emphasizing the high number of pigs under human care. Pigs in commercial production are housed indoors and continuously exposed to gasses such as ammonia. Several studies document that high ammoniaconcentrations may occur in indoor production with temporary levels raising to levels that cause concern for animal health. For instance mean ammonia levels in sow, weaner and finisher houses range between 4.5-17.8 ppm in the Netherlands (max level recorded 59.8 ppm), Germany (max level recorded 43.7 ppm) England (max level recorded 58.6 ppm) and Denmark (max level recorded 43.8 ppm) but with maximum recordings (temporary peaks) being considerable higher (Groot Koerkamp et al., 1998).

Jones et al. (2001) investigated the effect of acute and chronic exposure, of juvenile pigs, to ammonia (concentration of approximately 40 ppm). The authors found indications that prolonged exposure to these ammonia levels could be damaging to the olfactory apparatus, and hence to the sensory capabilities, of pigs. An ammonia concentration of 40 ppm is high and pigs may be expected to start displaying aversive behaviour at lower levels. Identifying these aversive levels is highly relevant as there is currently no scientific knowledge justifying the existing levels for air quality stated in the Swedish national regulations (max level 10 ppm NH3, 0,5 ppm H2S, (Anonymous, 2019), and within the EU no specification regarding air quality in pig barns has been established with regards to the welfare of the animals. 

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