Dynamics of Bacterial and Fungal Communities and Metabolites During Aerobic Exposure in Whole-Plant Corn Silages With Two Different Moisture Levels

Abstract

The study was aimed to investigate the effect of moisture content on microbial communities, metabolites, fermentation quality, and aerobic stability during aerobic exposure in whole-plant corn silages preserved long time to improve the quality and aerobic stability of the silage during feed-out. Corn plants with two different moisture levels (high-moisture content, 680 g/kg; low-moisture content, 620 g/kg) were harvested at one-third and two-thirds milk-line stages, respectively, ensiled in laboratory-scale silos, and then sampled at 350 day after ensiling and at 2 and 5 day after opening to investigate bacterial and fungal communities, metabolites, and aerobic stability. High-moisture content increased aerobic stability and pH and decreased lactic acid and microbial counts in silages (<i>P</i> < 0.05). During aerobic exposure, the low-moisture silages had higher pH and lactic acid bacterial count and lower lactic acid than the high-moisture silages (<i>P</i> < 0.05); <i>Acinetobacter</i> sp. was the most main bacterial species in the silages; <i>Candida glabrata</i> and unclassified <i>Candida</i> had an increasing abundance and negatively correlation with aerobic stability of high-moisture silages (<i>P</i> < 0.05), while <i>C. glabrata</i>, <i>Candida xylopsoci</i>, unclassified <i>Saccharomycetaceae</i>, and unclassified <i>Saccharomycetales</i> negative correlated with aerobic stability of low-moisture silages (<i>P</i> < 0.05) with a rising <i>Saccharomycetaceae</i>; the silages had a reducing concentration of total metabolites (<i>P</i> < 0.05). Moreover, the high-moisture silages contained greater total metabolites, saturated fatty acids (palmitic and stearic acid), essential fatty acids (linoleic acid), essential amino acids (phenylalanine), and non-essential amino acids (alanine, beta-alanine, and asparagine) than the low-moisture silages at 5 day of opening (<i>P</i> < 0.05). Thus, the high-moisture content improved the aerobic stability. <i>Acinetobacter</i> sp. and <i>Candida</i> sp. dominated the bacterial and fungal communities, respectively; <i>Candida</i> sp. resulted in the aerobic deterioration in high-moisture silages, while the combined activities of <i>Candida</i> sp. and <i>Saccharomycetaceae</i> sp. caused the aerobic deterioration in low-moisture silages. The greater aerobic stability contributed to preserve the palmitic acid, stearic acid, linoleic acid, phenylalanine, alanine, beta-alanine, and asparagine during aerobic exposure.