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

Authors: COBLENTZ, WAYNE; AKINS, MATTHEW - UNIVERSITY OF WISCONSIN; CAVADINI, JASON - UNIVERSITY OF WISCONSIN

Submitted to: Applied Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2021
Publication Date: 5/26/2021
Citation: Coblentz, W.K., Akins, M.S., Cavadini, J.S. 2021. Nutritive value, silage fermentation characteristics, and aerobic stability of 3 round-baled, perennial-grass forages ensiled with or without a propionic-acid-based preservative. Applied Animal Science. https://doi.org/10.15232/aas.2021-02157.
DOI: https://doi.org/10.15232/aas.2021-02157

Interpretive Summary: Baled silage techniques offer a forage conservation option that limits risk to valuable hay crops because less wilting time is required to reach normal recommended moisture targets (45 to 55%) compared to dry hay. One issue related to baled silage management occurs during feedout, when silage bales may be exposed to air for various reasons prior to consumption by livestock. This concern can be more problematic for bales wrapped with in-line wrapping systems, where partial or total removal of the plastic wrap prior to transport to the feeding site is unavoidable. Our research objectives were to compare the fermentation characteristics, nutritive value, and aerobic stability of 3 perennial cool-season grasses (meadow fescue, orchardgrass, and endophyte-free tall fescue) conserved as silages baled at relatively low moisture concentrations (31.1 to 42.1%) with or without a propionic-acid-based preservative. Application of the preservative at rates of 0.48 or 0.77% of wet bale weight provided additional aerobic stability compared to untreated bales after exposure to air. This response was consistent with previous findings for alfalfa-grass baled silages, and provides forage and livestock producers with an additional management tool for use within their operations. The preservative will add cost to producing baled silages, and may not be necessary or advised in all situations. However, use of preservatives may be justified in targeted situations where baled silages must be exposed to air prior to feeding, particularly during seasonal transition periods when ambient temperatures are greater than those during winter, and may accelerate the aerobic deterioration process.

Technical Abstract: Objective: Propionic-acid-based products are used commonly for storage of dry hay, but generally not for baled silages. Objectives for this study were 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. Materials and Methods: 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% prior to 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. Results and Discussion: 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 related (in part) to differences in bale moisture compared to meadow fescue. During a 14-d aerobic exposure period, the maximum surface temperature (0.15-m depth) was greater for controls compared to preservative-treated silages (33.4 vs 15.2oC; P <0.001), and exposed pH exhibited a similar response (5.76 vs. 5.26; P < 0.001). Implications and Applications: Application of a propionic-acid-based preservative improved aerobic stability in dry grass silages, but cost must be weighed in any decision prior to use.