Nutritive value, silage fermentation characteristics, and aerobic stability of round-baled, alfalfa-grass forages ensiled at 2 moisture concentrations with or without a propionic-acid-based preservative

Authors: Coblentz, Wayne; AKINS, MATTHEW - University Of Wisconsin

Submitted to: Applied Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2021
Publication Date: 3/22/2021
Citation: Coblentz, W.K., Akins, M.S. 2021. Nutritive value, silage fermentation characteristics, and aerobic stability of round-baled, alfalfa-grass forages ensiled at 2 moisture concentrations with or without a propionic-acid-based preservative. Applied Animal Science. https://doi.org/10.15232/aas.2020-02128.
DOI: https://doi.org/10.15232/aas.2020-02128

Interpretive Summary: Most state-of-the-art balers manufactured today come equipped with applicator systems for preservatives and/or inoculants, or the option exists for factory installation at the time of purchase. Within this context, propionic acid-based preservatives are available, and are used commonly, as preservatives for storage of dry hay, but not for baled silages. Our objectives for this study were to test several application rates of a propionic-acid-based preservative on the storage efficiency, nutrient preservation, fermentation characteristics, and subsequent aerobic stability of alfalfa-grass silages made at two moisture concentrations (51.6 or 43.6%) and damaged by a 0.2-inch rainfall event during wilting. The application of a propionic-acid-based preservative at rates of 0.13, 0.44, or 0.80% of wet weight, executed simply by engaging the different pumping options with the factory-installed applicator, showed some evidence of restricting overall silage fermentation. Preservative application, regardless of rate, was effective at improving the aerobic stability of alfalfa/grass baled silages compared to untreated controls. The 0.44 and 0.80% rates provided better stability than the lowest rate, and on a practical basis, were essentially equivalent within an 11-d exposure period. For a 4 × 4-ft round bale weighing 1250 lbs (50% moisture), about 5.5 lbs of product appeared to provide optimum benefit. While this option adds cost, it still may be a viable tool for overall production management, particularly in targeted situations where periods of exposure to air are likely before consumption by livestock. This may be particularly true during seasonal transitions before or after winter, when warmer temperatures may be less inhibiting of aerobic deterioration.

Technical Abstract: Objective: Propionic-acid-based products are used commonly for storage of dry hay, but they are not often considered when ensiling baled forages. Objectives for this study were to test several application rates of a propionic-acid-based preservative on the storage efficiency, nutrient preservation, fermentation characteristics and aerobic stability of alfalfa-grass silages. Materials and Methods: This study evaluated 4 preservative treatments applied to alfalfa-grass forages that had received 5.1 mm of unexpected rainfall during wilting. A propionic-acid-based preservative was applied at rates of 0.01 (control), 0.13, 0.44, or 0.80% of wet bale weight to 24 (1.2 × 1.2-m) round bales made at either 43.6 or 51.6% moisture. Aerobic stability was assessed by removing plastic film from all bales, and exposing bales to outside weather conditions during spring. Results and Discussion: Before fermentation, forage pH declined linearly (P < 0.001) from 6.14 to 5.77 across increasing product-application rates. After a 242-d storage period, there were linear increases in concentrations of total alcohols (P = 0.002), and particularly 2,3-butanediol (P < 0.001), as application rate increased. After aerobic exposure, maximum surface temperatures (0.15-m depth) were 55.6, 34.3, 22.7, and 17.9oC for the 0.01, 0.13, 0.44, and 0.80% rates, respectively, which represented a linear (P = 0.001) effect. A similar linear (P = 0.002) effect was observed for exposed surface pH (range = 6.52 to 5.41). Implications and Applications: Use of a propionic-acid-based preservative improved aerobic stability of round-bale silages, but the additional cost must be considered as part of any management decision.