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Fungal Growth During Fermentation and Refermentation of Nonprotein Nitrogen Treated Corn Silage¹

Department of Dairy Science, Michigan State University, East Lansing 48824

ABSTRACT

Chopped corn (35% dry matter) was treated with urea, aqua ammonia, or an ammonia-mineral suspension at 0, .23, .45, or .9% added nitrogen, placed in polyethylene bags (containing 56 kg) inside 200 liter metal drums, evacuated, and sealed. During fermentation, silages were sampled and temperatures measured on days 0, 5, 20, and 86. On day 86 of fermentation, two 12-kg portions were placed in open containers at 25 C. On days 0, 7, 21, and 28 of refermentation, silages were sampled, aerated, and temperatures were measured. All silages were analyzed for lactic acid, pH, and number and type of fungi. Initial and final pH values were increased by urea but most with ammonia. During refermentation, all nitrogen sources produced large pH increases. Addition of .23% nitrogen as ammonia stimulated lactic acid, but more depressed lactate production. Lactic acid disappeared during refermentation. Silages treated with the ammonia-mineral suspension required the longest time for appearance of visible fungi. Total fungal counts fell more rapidly on ammonia treatments, but additives did not differ on days 5 and 20 of fermentation. Despite large variations, all sources at all percents of nonprotein nitrogen depressed fungal counts during refermentation with the .45 and .9% nitrogen treatments showing lower counts than 0 and .23%. Treatments did not change the relative proportions of fungi during spoilage. Yeasts dominated prior to and throughout fermentation, and Geotrichum increased during refermentation. Some Penicillium and Aspergillus were identified, but they never comprised a major proportion of the total counts.

¹ Published with the approval of the Director of the Agricultural Experiment Station as Journal Article No. 7096.

² Department of Animal Science, Eastern Kentucky University, Richmond 40475. Partially supported by NIH Training Grant GM01818.