Occurrence of fungal species in stored alfalfa forage as influenced by moisture content at baling and temperature during storage

Abstract

A study was conducted to evaluate the effect of moisture content at baling on fungal growth during storage of alfalfa forage. Alfalfa forage was baled at DM contents of 64.1–66.2% (Low), 71.9–73.2% (Medium) and 75.4–77.4% (High) and was sampled 1, 2, 3, 4, 5, 6, 7, 8, 9, 14, 21, 35 and 60 d after storage. For each sample, abundance of fungal and yeast species was assessed by plating on media. Total fungal counts, number of species, species diversity, and species dominance were subjected to analysis of variance, and variation in the fungal assemblages was characterized by ordination. Total fungal counts, number of species, species diversity, and species dominance were not influenced (P > 0.05) by moisture content in the early (days 1 to 8) storage phase. Moisture content at baling did influence (P < 0.05) total counts, number of species, and species dominance in the latter phase (days 9 to 60) of storage. Total fungal counts were highest in Low DM forage, and number of species highest in Medium DM forage. Species dominance was highest in High DM forage. Low DM forage was associated with Aspergillus fumigatus, Mucor spp., Absidia spp., Emericella nidulans, and thermotolerant hyphomycetes. Aspergillus repens, Absidia spp. and some yeasts were more predominant in Medium and High DM forages. Moisture content and temperature were related to species assemblages during storage but water-soluble carbohydrate concentration, crude protein concentration and total bacteria counts were not. "Field" fungi, Phoma, Alternaria, Cladosporium spp. and most yeasts were eliminated within 8 d of storage. Physical conditions created in the early stages of storage likely affected fungal growth in the later storage phase. Key words: Moisture content, temperature, storage, alfalfa hay, fungal species, diversity