Nitrogen dioxide (silo gas) poisoning in pigs.

Investigations were conducted on the composition of silo gas and its effects in pigs which inhale it, and comparison was made of lesions of silo gas toxicosis in pigs and those described for silo-filler's disease in man. Caged pigs were exposed for varying periods to the silo gas by placing them in recently filled silos or within an enclosure formed with plastic sheets at the bottom of a silo chute. Pigs inhaling a high concentration of silo gas for periods longer than 10 minutes died in 21 to 72 minutes. Composition of the silo gas as determined by mass spectrometer analysis was 0.173 to 9.05% carbon dioxide, 0 to 140 p.p.m. of nitric oxide, and 8 to 360 p.p.m. of nitrogen dioxide. In pigs dying from inhaling silo gas, the early lesions were pulmonary alveolar edema and hyperemia. Large amounts of alveolar fibrin were present in pigs that survived the longest. In addition, there were hemorrhage, bronchiolar and bronchial epithelial desquamation, and perivascular, interlobular, and subpleural edema. Pigs surviving the acute effects of silo gas toxicosis did not develop bronchiolitis fibrosa obliterans (BFO) as described for silo-filler's disease in man. 25 references, 5 figures, 2 tables.