Aversion of pigs and domestic fowl to atmospheric ammonia

Abstract

Housed pigs and domestic fowl are exposed chronically to atmospheric ammonia at concentrations that may exceed 30 ppm in buildings with poor environmental control. While the effects of ammonia on animal performance and health are reasonably well understood, the effects on behavior are not. In a series of experiments, we therefore studied the aversion of weaner pigs, broiler chickens, and adult laying hens to atmospheric ammonia in a choice test. Typically, individual or small groups of animals were kept in a multi-compartment exposure chamber for one or two weeks. The physical environment in all eight compartments of the chamber was identical in all respects but one: the concentration of atmospheric ammonia was set at approximately 0, 10, 20, or 40 ppm. Observations of the animals' location and behavior were used to indicate their aversion to ammonia. Both pigs and domestic fowl (of both strains) significantly preferred fresh air (approximately 0 ppm) to an ammoniated atmosphere. Visit duration and frequency declined with increasing ammonia concentrations, although interestingly, both species showed a delayed avoidance of ammonia, perhaps indicative of a sense of malaise, which was only manifested after about 30 to 60 min. When given a forced choice between thermal comfort and access to fresh air, cold-stressed pigs chose the former over the latter. Overall, pigs and fowl did not always make short-term choices that were necessarily in their long-term interests. Further work is in hand to study the strength of this aversion in fowl. Current recommendations for air quality in pig and poultry houses should be revised to take account of the animal's strong preference for fresh air; our findings indicate limited tolerance of ammonia at concentrations typical of current housing systems.