The impact of chronic environmental stressors on the social behaviour of growing pigs, Sus scrofa

Abstract

Introduction The effects of common and current environmental stressors on the social behaviour of farm animals are poorly understood and have never before been tested in controlled conditions. Here, we report the results of a longitudinal, multi-factorial experiment designed specifically to examine the individual, additive or interactive effects of elevated ammonia, noise and dim light levels on the social behaviour of growing pigs under strictly controlled environmental conditions. Material and methods Two batches of 126 4-week-old hybrid gilts (50% Pietrain, 25% white Duroc, 12.5% Large White, 12.5% Landrace) were obtained at weaning. Eight rooms were allocated to eight experimental treatments in a 23 multifactorial design. Each treatment comprised elevated or low levels of light intensity (nominally 200 vs. 40 lux), atmospheric ammonia concentration (nominally 20 ppm) and dim light intensities (<40 lux) can affect aggression in pigs. Aggression in pigs is signalled with odour and visual cues. Group-mate recognition can be olfactory, and odour cues may be masked by the ammonia, affecting perception and modulating the formation of stability in the group. The findings reported here may have implications for the welfare of farmed pigs in the UK. Ventilation systems should be designed further to minimise the aerial ammonia concentrations to avoid potential exacerbation of aggressive acts early in the development of the pigs. In addition, it seems that dim lighting may increase aggressive acts, again, early in the development of the pigs, and the industry should take account of this when designing facilities in the future