Storage characteristics of baled alfalfa-grass forages treated with a propionic-acid-based preservative or wrapped in stretch plastic film

Authors: Coblentz, Wayne; AKINS, MATTHEW - University Of Wisconsin; KIEKE, BURNEY - Marshfield Clinic Research

Submitted to: Applied Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2021
Publication Date: 9/28/2021
Citation: Coblentz, W.K., Akins, M.S., Kieke, B. 2021. Storage characteristics of baled alfalfa-grass forages treated with a propionic-acid-based preservative or wrapped in stretch plastic film. Applied Animal Science. 37(5):505-518. https://doi.org/10.15232/aas.2021-02193.
DOI: https://doi.org/10.15232/aas.2021-02193

Interpretive Summary: For this study, the application of plastic film onto relatively dry alfalfa-grass forages (25.8%) using field procedures identical to those used commonly for wetter baled silages proved extremely effective in reducing spontaneous heating during storage, as well as minimizing nutrient losses during this time interval. This management approach shows promise as an alternative to various preservatives for conserving forages in humid environments, or when unstable weather prohibits desiccation of forages to acceptable moisture targets for safe storage as dry hay. Potentially, this is particularly relevant in circumstances when forage approaches suitability for safe storage as dry hay, but weather conditions will not allow the remaining drying necessary for safe storage in this manner. The production of fermentation acids and associated pH depression were greatly restricted in these dry silages, suggesting preservation was accomplished primarily by exclusion of oxygen, and that maintaining anerobic conditions within the bale is critical for long-term storage. Furthermore, application of plastic wrap under these conditions should effectively eliminate the effects of weathering that are commonly observed with outdoor storage of round-baled hay. Although the propionic-acid-based preservative numerically reduced spontaneous heating at various time points throughout the 84-day storage period, neither the magnitude, nor the consistency, of these reductions were sufficient to generate statistically significant responses, unless unwrapped bales were analyzed independently from from those wrapped in plastic.

Technical Abstract: Objective: Objectives for this study were to assess the storage characteristics of relatively dry mixed-species forage preserved with a propionic-acid-based preservative, or by wrapping with 7 layers of plastic film as baled silage. Materials and Methods: The experimental design was a randomized complete block with a 2 × 2 factorial arrangement of treatments, which included application of a propionic-acid-based preservative at 0.27 ± 0.025% of wet bale weight (yes or no) and wrapping in 7 layers of stretch film (yes or no). A total of 33 round bales (1.2 × 1.5 m) containing 66% legumes (alfalfa) and 31% grasses (orchardgrass) were produced at 25.8 ± 2.20% moisture. Bales were positioned on wooden pallets for 84 d before final sampling. Internal bale temperatures were monitored daily during the 84-d storage period. Results and Discussion: Generally, there were no interactions (P > 0.05) of main effects observed. The preservative had no statistical effect on any measure of spontaneous heating (P = 0.103). In contrast, application of plastic film yielded reduced maximum internal bale temperatures (41.3 vs. 61.3oC; P < 0.001) and total heating degree days > 30oC (92 vs. 722; P < 0.001) when compared to unwrapped bales. These reductions in spontaneous heating also were reflected in measures of nutritive value, where NEl was reduced in unwrapped bales by 9.9% (P < 0.001), but only by 1.4% (P > 0.05) in wrapped bales compared to pre-storage values. For wrapped bales, application of the preservative resulted in a more acidic final pH (5.84 vs. 5.95; P = 0.020), but fermentation was very restricted within all bales. Implications and Applications: The application of plastic film onto relatively dry mixed-species forages using baled silage techniques proved extremely effective in reducing spontaneous heating during storage, as well as minimizing nutrient losses.