Aerobic deterioration in corn silage relative to the silo face

Movement of oxygen and subsequent microbial development and heating in corn silage were measured over four days at 5, 20, 35, and 50 cm from the exposed face in laboratory-scale (60 ¥ 15.5 cm diameter) PVC silos. In all six trials, most microbial activity occurred at the 5-cm level. Acetic acid bacteria initiated heating in all trials although yeasts were significant in two trials. Bacilli were not important until silage pH was above 5 and were associated with a secondary temperature rise in four trials. Oxygen entering the silage at the open face was utilized principally near the face, and temperatures above 40° C were observed only at the 5-cm level. Heating at 20 cm occurred in all trials, but appeared to result from heat transfer from the active zone rather than from microbial activity at that depth.