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Digestibility vs. energy
Climate-related challenges are becoming greater from year to year. The strategic task of achieving a balance between yield and nutritional quality of silage is increasingly demanding. Maize silage makes up 50% or more of many rations and has a decisive influence on digestible structural components. High-yield dairy cows require a ration with a fiber content of more than 25%. This makes silage digestibility a crucial factor for the overall energy content of the ration.
The cob – the golden part
Starch from the cob is the most important soluble carbohydrate. Its concentration is directly linked to plant maturity. Starch accumulation occurs when sugar concentration in the dry matter reaches its peak. This happens within a period of one to two weeks. After that, the concentration either increases slowly or plateaus. However, energy in maize silage does not come only from starch (typically 30–40% of DM), but also from digestible cell walls, which make up about 45% of the maize plant DM.
Maximum starch = less sugar
To maximize starch accumulation in the grain, harvest is often delayed, which leads to higher dry matter content. Due to ongoing respiration (even when photosynthesis is reduced), sugar levels drop by about 5 g per kg DM per day. While this may seem small, on 1 hectare with 16 tons of DM it equals a loss of about 80 kg of sugar per day. Remember: sugar is the main energy source for silage bacteria. The drier the maize, the worse the compaction—and the greater the negative consequences.
Stay-green for silage?
Stay-green varieties are bred so that the grain dries quickly while stalks and leaves remain moist, keeping the plant green. While this is desirable in grain production, it must be treated with caution in silage maize. Rapid grain drying can reduce starch digestibility.
The fiber fraction
One key parameter for digestibility is neutral detergent fiber (aNDFom), which indicates fiber quality. This fraction consists of hemicellulose, cellulose, and lignin. As with plant cell walls, maturity (% DM) directly affects the availability of these components. Lignification, maturation, and cell wall thickening can reduce aNDFom degradability. In addition, the proportion of resistant starch increases with plant maturity, which must be considered depending on the ration.
Harvest timing guideline
An optimal harvest time is typically at 30–35% DM of the whole plant. The cob should be in the middle of the dough stage—firm but still easily indented with a fingernail. Note: in drought conditions, harvest may need to take place earlier to maintain a silageable and digestible plant material.
Fermentation
The rapid conversion of sugars into fermentation acids by lactic acid bacteria is key for producing high-quality silage. One way to improve fermentation is the use of specialized silage inoculants, which effectively reduce nutrient losses. The faster the pH drops, the better.
More digestible with silage additives
The combined use of homo- and heterofermentative bacteria has proven particularly effective. Together, they ensure rapid pH reduction, protection against reheating, and improved palatability. Trials have shown improved digestibility of dry matter and NDF with such bacteria.
Starch alone is not enough
High starch content alone is not sufficient. Late harvest reduces digestibility and energy in the remaining plant. The later the harvest and the higher the dry matter, the more difficult proper chop length becomes, the harder compaction gets, the higher the risk of reheating, the more mold spores are present, and the lower feed intake becomes.
