Impact of long-term storage on alfalfa leaf and stem silage characteristics

Authors: SIKORA, MIRANDA - University Of Wisconsin; HATFIELD, RONALD - Retired ARS Employee; Kalscheur, Kenneth

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2021
Publication Date: 12/10/2021
Citation: Sikora, M.C., Hatfield, R.D., Kalscheur, K. 2021. Impact of long-term storage on alfalfa leaf and stem silage characteristics. Agronomy Journal. 11(12). Article 2505. https://doi.org/10.3390/agronomy11122505.
DOI: https://doi.org/10.3390/agronomy11122505

Interpretive Summary: The goal of this study was to determine whether alfalfa leaves and alfalfa stems separated by a mechanical leaf stripper could be ensiled and stored over a long period of time and result in good quality silage for ruminants. Harvesting leaves separate from stems allows for a longer harvest interval because leaf quality does not change as rapidly as stem quality as plants mature. One challenge of harvesting and ensiling alfalfa leaves is its high moisture content. This research demonstrated that high moisture leaf silage was stable and could be stored successfully up to 350 days without significantly affecting quality. High moisture stem fractions did not ferment well and decreased in quality after ensiling, suggesting that stem silage should be fed soon after ensiling. Ultimately, separating leaves from stems during harvest allows for the creation of two separate feedstocks that can be recombined in appropriate ratios to provide proper protein and fiber concentrations in ruminant diets. This research will be of interest to alfalfa producers, dairy producers, nutritionists, and researchers interested in alternative harvesting methods for alfalfa that can create unique feedstuffs to meet the nutrient requirements of ruminant livestock.

Technical Abstract: Fractionation of alfalfa (Medicago sativa L.) into leaves and stems can reduce cutting frequency while producing a high-value feedstuff. A difficulty with fractionation is the higher moisture content at ensiling due to the inability to wilt leaves without substantial dry matter loss or financial cost. To evaluate whether the silage quality of fractionated alfalfa is competitive with conventional methods under long-term storage conditions, high-moisture leaves (250–280 g·kg-1 dry matter, DM) and stems (190–240 g·kg-1 DM) were ensiled for 21 and 350 days and compared to wilted whole-plant silage for two alfalfa developmental stages. At 21 days, leaf and whole-plant silage fermentation characteristics indicated suitable lactic acid bacterial fermentation through decreased pH, high lactic acid–to-acetic acid ratio, and a lack of clostridial fermentation. At 350 days, leaf silage fermentation and nutritional quality decreased due to sustained proteolysis, but true protein still exceeded that of whole-plant silage. High-moisture stem fractions fermented poorly; at 21 days, stage 3 stems had significant amounts of butyric acid, while stage 5 stems became clostridial at 350 days. Long-term storage of high-moisture leaf silages can produce good-quality silage despite exceeding moisture contents typically recommended for alfalfa, while wilting is required for stem silages