Microbial populations, fermentation end-products, and aerobic stability ofcorn silage treated with ammonia or a propionic acid-based preservative

We studied the effects of ammonia treatment on microbial populations during the fermentation of corn silage. We also compared the effects of ammonia t o a preservative containing buffered propionic acid and other antifungal co mpounds on the fermentation and aerobic stability of corn silage. In the fi rst experiment, whole-plant corn was ensiled without treatment or treated w ith ammonia-N to supply an additional 0.3% N (fresh-forage basis). The addi tion of ammonia immediately increased silage pH and had no effect on number s of lactic acid bacteria, but delayed their growth compared with untreated silage. Numbers of enterobacteria declined more slowly, but numbers of yea sts and molds declined more quickly in silage treated with ammonia. During the early stages of ensiling, lactic acid increased more rapidly in untreat ed than in treated silage. The reverse was true for acetic acid concentrati ons. When exposed to air, growth of yeasts and molds was delayed in ammonia -treated silage. In a second experiment, various levels (0.1 to 0.3%, fresh weight) of ammonium-N or a preservative with buffered propionic acid were added to whole-plant corn and allowed to ensile for 106 d. Silage treated w ith ammonia had a greater ratio of L- to D-lactic acid than did other silag es. Untreated silage was aerobically stable for 32.3 h, whereas the low (42 h) and moderate (52.7 h) concentrations of both additives numerically impr oved aerobic stability. High concentrations of ammonia-N (0.3%) or a buffer ed propionic acid preservative (0.3%), markedly improved the aerobic stabil ity of corn silage (82 and 69 h for ammonia and propionic acid-treated sila ge, respectively).