Effect of storage temperature and time on fermentation and nutritive value of sorghum-sudangrass silage

Authors: COONS, ELIZABETH - Rock River Laboratory, Inc; Akins, Matthew

Submitted to: Applied Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Harvesting of cold or frozen forage in late fall or early winter may limit silage fermentation and stability of the silage when feeding due to continued low temperature of the stored forage. Sorghum-sudangrass forage was harvested and ensiled in mini-silo vacuum seal bags, then stored at either room temperature (20°C) or in a refrigerator (4°C). Silage was stored for up to 60 days then analyzed for fermentation and feed quality. Storage at 4°C slowed the fermentation process and limited conversion of sugars to silage acids compared to storage at 20°C. Silage stored at 4°C also had lower fiber levels due to less fermentation. However, the silage stored at 4°C was less stable when exposed to air and heated more quickly (47 hours stable) than silage stored at 20°C (149 hours stable). Harvesting of cold or frozen forage would limit silage fermentation, thus it is recommended to allow forage to thaw/warm prior to harvesting.

Technical Abstract: Objective: The study evaluated the fermentation and nutritive value of freeze-affected sorghum-sudangrass silage stored at two temperatures. Materials and Methods: Sorghum-sudangrass forage affected by several frost/freeze events and lodging was harvested and chopped, then ensiled in vacuum sealed plastic mini-silos. Silos were stored at either 4°C or 20°C for 5, 10, 15, 30 or 60 days with triplicate silos at each time. Resulting silage was evaluated for pH, silage acids and alcohols, nitrates, and nutritive value. Aerobic stability was also measured on silages stored for 60 days. Results and Discussion: Silage pH decreased more quickly when stored at 20°C with a 10-day lag before pH decreased when stored at 4°C. Lactic, acetic, and propionic acid concentrations were greater at all times for silage stored at 20°C. Ethanol and methanol were also higher in silage stored at 20°C likely due to presence of wild yeasts in the forage. Aerobic stability however was greater for silage stored at 20°C (149 h) compared to 4°C (47 h). Having less fermentation for silage stored at 4°C resulted in 1% greater DM recovery. Silage storage at 4°C also resulted in lower NDF concentration due to less silage acid production, with no other changes in nutritive value observed due to storage temperature. Nitrate concentrations were low in the initial forage (76 ppm DM) with concentrations lower after storage (43-50 ppm DM). Implications and Applications: Storage temperature of sorghum-sudangrass silage had a significant impact on silage acid production and aerobic stability with limited fermentation the first 10-15d of storage. This research is applicable when harvesting forage during cold or freezing temperatures which limits early fermentation. Allowing standing forage to thaw/warm prior to harvest may improve fermentation. Additional research on changes in nitrate of frosted sorghum forage is needed due to low initial levels in this study.