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Elevated concentrations of atmospheric ammonia (∼20 v. <5 ppm) and LL intensity (∼40 v. 200 lux) had the most pronounced effects, particularly on the nature of social interactions, with pigs under these conditions showing more aggression in the early stages of the experiment. In addition, pigs exposed to a high level of mechanical noise representative of artificial ventilation (∼80 v. 40 dB [A]) were less submissive to aggressive acts, while pigs in ∼20 ppm ammonia showed more reciprocated aggression when in coincident LL (<40 lux).
The results indicate that atmospheric ammonia at commonly experienced concentrations may undermine social stability, particularly in the presence of low lighting, though the mechanisms are currently unknown. These findings have implications for the welfare of growing pigs and hence policy makers and farmers alike, with respect to the improvement of welfare in intensive pig farming.
M.O. Parker, E.A. O’Connor, M.A. McLeman, T.G.M. Demmers, J.C. Lowe, R.C. Owen, E.L. Davey, C.M. Wathes and S.M. Abeyesinghe. The impact of chronic environmental stressors on growing pigs, Sus scrofa (Part 2): social behaviour.animal (2010), 4: 1910-1921.
