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At GFW, our farm team are experts in collecting, interpreting, and advising farmers on silage analysis, helping to maximise nutritional value, encourage desirable fermentation, and optimise feed-out strategies.
Silage dry matter (DM) is a highly variable characteristic, influenced by farm practices, seasonal conditions, and the cut of forage. Analyses have shown that DM can range widely, from 15–55% in clamp silage to 17–79% in big bales. While visual assessment such as squeezing the silage and observing water release can provide a rough indication, DM can vary significantly across the clamp. For accurate, up-to-date monitoring, frequent sampling combined with Near-Infrared (NIR) analysis is recommended.
The DM of silage plays a crucial role in successful conservation, or ‘pickling’, and also affects clamp management and feed-out quality. DM directly influences the type of fermentation that occurs during ensiling: the desirable homofermentation, or the less favourable heterofermentation. Both pathways rely on glucose derived from water-soluble carbohydrates (WSC) in the forage, but homofermentation is the most efficient route because it produces primarily lactic acid, which is the strongest of acids, which rapidly lowers pH. In contrast, heterofermentation generates a mix of acids along with ethanol and carbon dioxide, with less lactic acid produced, resulting in lower preservation efficiency.
When silage DM is within the optimal range, around 30–35% for grass, it requires less acid to achieve effective pickling because the lower water content reduces the forage’s buffering capacity. With less water, the acids produced by lactic acid bacteria are more concentrated, allowing the pH to drop quickly and stabilise the silage with minimal acid production. This rapid acidification helps preserve sugars and maintain the nutritional quality of the forage. By comparison, wetter forage has a higher water content, which dilutes acids and increases buffering. More lactic acid is therefore required to achieve the same pH reduction, prolonging fermentation and depleting water-soluble carbohydrates and increasing the risk of undesirable microbial activity.
To assess whether silage has undergone favourable homofermentation, analysis of lactic acid relative to other volatile fatty acids (VFA) is essential. Ideally, the lactic acid concentration should be approximately three times that of the VFA, indicating efficient preservation and high silage quality. Regular monitoring of DM and fermentation products, combined with proper harvest timing, wilting, and clamp management, is therefore critical to producing silage that is both nutritious and stable.
“Understanding your silage’s dry matter helps you make better day-to-day decisions,”
says Olivia Ward, Farm Business Consultant at GFW.
“It influences how the crop ferments, feeds out, and performs in the ration. Regular sampling and analysis give farmers the confidence to adjust practices and get the most from every cut.”
The GFW Rural Team can help advise on and interpret silage analysis, offering practical insight on how to enhance silage quality through tailored on-farm practices.
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