BEHAVIORAL-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 oct agonally shaped (annular), eight compartment preference chamber was bu ilt to house the pigs. Each compartment supplied the pigs with ample f ood, water and bedding material but differed in the level of atmospher ic contamination. Adjacent compartments were separated by plastic curt ains, allowing the pigs free access to neighbouring compartments while reducing cross-contamination of the pollutant. The position of the co ntamination was changed weekly to eliminate positional preferences. Th e location of the pigs was scan sampled every 15 min and their behavio ur 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 da ys that each group inhabited the chamber (P >0.05). The occupancy patt ern was resumed following the rotation of the ammonia concentrations a nd/or following cleaning (P >0.05). Higher concentrations of ammonia w ere 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 th e aversion was not immediate, it is suggested that aversion was not du e to the odour of ammonia initially experienced on entry. Instead the insidious aversion may be due to a sense of malaise that may develop w hile a pig is in a polluted atmosphere. The pigs chose to rest (P=0.00 2), sit (P=0.007), feed (P=0.007) and forage (P=0.013) more in the unp olluted compartments. Overall more feeding behaviour was observed in t he fresh air and more food was consumed in these compartments of the c hamber (P=0.002).