Behavioural responses of pigs to atmospheric ammonia in a chronic choice test

The behaviour of two groups of four pigs in concentrations of ammonia gas that are frequently recorded in piggeries (0, 10, 20 and 40 p.p.m.), was continuously observed for 14 days each in a choice test. An octagonally shaped (annular), eight compartment preference chamber was built to house the pigs. Each compartment supplied the pigs with ample food, water and bedding material but differed in the level of atmospheric contamination. Adjacent compartments were separated by plastic curtains, allowing the pigs free access to neighbouring compartments while reducing cross-contamination of the pollutant. The position of the contamination was changed weekly to eliminate positional preferences. The location of the pigs was scan sampled every 15 min and their behaviour at this time was instantaneously recorded. A significantly greater proportion of their time was spent in the unpolluted compartments (53.4%) than in the 10 p.p.m. (26.9%), 20 p.p.m. (7.1%) or 40 p.p.m. (5.1%) compartments (P <0.001). This avoidance was maintained for the 14 days that each group inhabited the chamber (P >0.05). The occupancy pattern was resumed following the rotation of the ammonia concentrations and/or following cleaning (P >0.05). Higher concentrations of ammonia were visited less often (P=0.005) and once there, the pigs stayed for a comparatively shorter time (P=0.003) -for approximately 35 min. As the aversion was not immediate, it is suggested that aversion was not due to the odour of ammonia initially experienced on entry. Instead the insidious aversion may be due to a sense of malaise that may develop while a pig is in a polluted atmosphere. The pigs chose to rest (P=0.002), sit (P=0.007), feed (P=0.007) and forage (P=0.013) more in the unpolluted compartments. Overall more feeding behaviour was observed in the fresh air and more food was consumed in these compartments of the chamber (P=0.002).