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 (P < 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 (P < 0.05); Acinetobacter sp. was the most main bacterial species in the silages; Candida glabrata and unclassified Candida had an increasing abundance and negatively correlation with aerobic stability of high-moisture silages (P < 0.05), while C. glabrata, Candida xylopsoci, unclassified Saccharomycetaceae, and unclassified Saccharomycetales negative correlated with aerobic stability of low-moisture silages (P < 0.05) with a rising Saccharomycetaceae; the silages had a reducing concentration of total metabolites (P < 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 (P < 0.05). Thus, the high-moisture content improved the aerobic stability. Acinetobacter sp. and Candida sp. dominated the bacterial and fungal communities, respectively; Candida sp. resulted in the aerobic deterioration in high-moisture silages, while the combined activities of Candida sp. and Saccharomycetaceae 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.
Highlights
Corn is the most common crop for ensiling and the main forage source for ruminants worldwide because of the high biomass yield, suitable starch concentration, and good fermentation quality (Khan et al, 2015; Keshri et al, 2018; Guan et al, 2020; Zhang et al, 2020)
The time of high-moisture silages with 2◦C above the ambient temperature was longer than lowmoisture silages (P < 0.05) (Figure 1)
The whole-plant corn silage has become a predominant forage for dairy industry worldwide (Ferraretto et al, 2018) and is produced for feeding dairy cow throughout year
Summary
Corn is the most common crop for ensiling and the main forage source for ruminants worldwide because of the high biomass yield, suitable starch concentration, and good fermentation quality (Khan et al, 2015; Keshri et al, 2018; Guan et al, 2020; Zhang et al, 2020). The effects of different moisture content (high- and low-moisture content) or harvesting stages (one- and two-third milk-line stage) on the fungal community and metabolites in whole-plant corn silages remain unclear. Previous studies revealed the microbial community dynamics in whole-plant corn silages inoculated with lactic acid bacteria (LAB) (Keshri et al, 2018; Xu et al, 2020b) and derived from materials obtained from three areas in Iran (Gharechahi et al, 2017). Keshri et al (2018) examined the bacterial and fungal communities of whole-plant corn silages at 5 day after aerobic exposure. Little is known regarding bacterial and fungal community dynamics in whole-plant corn silages during aerobic exposure, especially at the species level. The SMRT is considered suitable for precisely assessing the microbial community at the species level in silage (Guo et al, 2018; Xu et al, 2019, 2020a,b)
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