Nutritive value, silage fermentation characteristics, and aerobic stability of 3 round-baled, perennial-grass forages ensiled with or without a propionic-acid-based preservative

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Propionic-acid-based products are used commonly for storage of dry hay but generally not for baled silages. The objective for this study was to compare perennial-grass-silage bales made with 2 application rates of a propionic-acid-based preservative against untreated controls for storage efficiency, nutrient preservation, fermentation characteristics, and aerobic stability. This study evaluated 3 preservative treatments applied to 3 perennial-grass forages (meadow fescue, orchardgrass, or tall fescue) that had been field wilted to respective moisture concentrations of 31.1, 42.1, or 41.4% before baling. A propionic-acid-based preservative was applied at rates of 0.01 (control), 0.48, or 0.77% of wet bale weight to 24 round bales. After an 84-d storage period, aerobic stability was assessed by exposing bales to outside weather conditions during October for 14 d. On a pre-ensiled basis, preservative application increased ( P < 0.001) buffering capacity and decreased ( P < 0.001) initial pH relative to control bales. After storage, orchardgrass silages exhibited greater ( P < 0.05) concentrations of lactic and total acids than other forage types, which was partially related to differences in bale moisture compared with meadow fescue. During a 14-d aerobic exposure period, the maximum surface temperature (0.15-m depth) was greater for controls compared with preservative-treated silages (33.4 vs. 15.2°C; P < 0.001), and exposed pH exhibited a similar response (5.76 vs. 5.26; P < 0.001). Application of a propionic-acid-based preservative improved aerobic stability in relatively dry grass silages, but cost must be weighed in any decision before use.