Effects of gestation pens versus stalls and wet versus dry feed on air contaminants in swine production

Objective: Evolving production practices in the swine industry may alter the working environment. This research characterized the influence of stall versus pen gestation housing and wet versus dry feed in finishing on air contaminant concentrations. Methods: Eight-hour time-weighted ammonia, hydrogen sulfide, respirable dust, respirable endotoxin, and carbon dioxide concentrations and temperature were measured regularly at stationary locations throughout a year in a facility with parallel gestation stall and open pen housing and parallel finishing rooms using dry and wet feed delivery systems. Hazard indices were calculated using ammonia, hydrogen sulfide, and endotoxin concentrations and relevant occupational exposure limits. Statistical analyses were performed to assess the influence of time of year, housing, and feed on measured parameters. Results: Due to reductions in ventilation rates as outdoor temperatures decreased, season affected pollutant levels more than other factors, with concentrations approximately one order of magnitude greater in winter than during summer. Ammonia, dust, and endotoxin were 25%, 43%, and 67% higher, respectively, on average, in the room with gestation pens than in the room with stalls. Endotoxin concentrations were more than five times higher, on average, with the dry feed system than with wet feed. While individual contaminant concentrations were generally below regulatory limits, hazard index calculations suggest that the effects of combined exposures on respiratory health may present a risk to workers. Elevated levels of respirable endotoxin and hydrogen sulfide were observed during power washing. Conclusions: Ventilation changes in response to seasonal requirements influenced air contaminant concentrations more than production practices, especially housing type. Wet feed systems substantially reduced airborne endotoxin concentrations.