Start with the risk, not the product
Silage additives can help support the fermentation process, limit undesirable microorganisms or improve silage stability after opening. However, the additive must match the specific conditions and the intended effect.
A silage additive cannot replace the correct harvest timing, clean forage, adequate compaction, rapid exclusion of oxygen or a sufficient feed-out rate. Simply increasing the application rate cannot reliably compensate for shortcomings in these areas.
The first question should therefore not be, “Which product should we use?” but rather, “Which risk do we need to control?”
Determine the required mode of action
The DLG classifies silage additives according to independently demonstrated efficacy categories. These include, in particular:
- Improving the fermentation process in forage with different degrees of ensilability
- Improving aerobic stability, meaning stability when exposed to air
- Limiting the growth of clostridia
- Other specific effects, where these have been demonstrated for the respective additive
This distinction is important. An additive that supports rapid acidification is not automatically the best solution for preventing heating after opening. Conversely, an additive intended to improve aerobic stability may not be suitable for every wet or difficult-to-ensile forage.
EU authorisation and independent proof of efficacy are not the same. Authorisation determines whether and under which conditions an additive may be used. Additional independent testing, by contrast, demonstrates a particular effect within a defined range of application.
Biological silage additives: targeted fermentation management
Biological silage additives contain selected lactic acid bacteria. Their properties vary depending on the bacterial culture and strain.
Homofermentative lactic acid bacteria convert fermentable sugars primarily into lactic acid. Under suitable conditions, this can accelerate the decline in pH and support the desired fermentation process. Their main purpose is controlled acidification. However, improved stability after opening the silo does not automatically follow.
Heterofermentative cultures also produce other metabolites that can help limit yeast growth. When correctly selected and applied, they can support aerobic stability. This is particularly relevant for silages that tend to heat after opening and exposure to air.
The result depends on factors including forage type, dry matter content, sugar content, bacterial strain, application rate, distribution and storage period. For biological additives, the requirements concerning water quality, temperature, storage life of the prepared solution and minimum fermentation period must also be observed.
Chemical silage additives: direct action under higher-risk conditions
Chemical silage additives often contain organic acids, their salts or carefully formulated combinations. Depending on their composition, they can support acidification or limit undesirable bacteria, yeasts and moulds.
Such solutions may be particularly useful for difficult-to-ensile, wet, highly buffered or contamination-prone forage. An appropriate chemical solution may also be considered for very dry material that is difficult to compact or where there is a pronounced risk of heating after opening.
However, not every formulation provides the same effect. The decisive factors are the specific active-ingredient profile, the authorised conditions of use, the prescribed application rate and uniform distribution throughout the forage.
The label, safety data sheet, equipment and material compatibility, and personal protective measures must be observed during application. The prescribed application rate or formulation should not be altered independently.
Assess typical starting conditions correctly
The following points provide an initial guide:
- For wet, low-sugar or difficult-to-ensile forage, supporting the fermentation process is often the primary objective.
- For maize silage, whole-crop silage, drier material, low feed-out rates or recurring heating, aerobic stability is usually the central concern.
- Where there is an increased risk of undesirable fermentation or clostridia, an additive with the corresponding independently demonstrated efficacy should be selected.
- Biological systems can reach their limits in very dry forage that is difficult to compact. In such conditions, an appropriately tested chemical solution may offer a more robust option.
- If a silo must be opened early, only an additive expressly suitable for a shorter storage period should be used. Otherwise, an adequate fermentation period remains necessary.
This initial assessment does not replace an evaluation of the individual farm, forage and intended additive.
Application rate and distribution are decisive
The intended effect can only be achieved if the additive is applied in accordance with its authorisation and product instructions. The application equipment should be inspected and calibrated before harvesting and adjusted to the actual forage throughput.
Uniform distribution throughout the forage is equally important. Applying the correct total quantity is not sufficient if individual areas are underdosed or remain untreated.
Where heating repeatedly occurs after opening, the application rate should not simply be increased. Compaction, film integrity, edge sealing, the exposed silo face, feed-out hygiene and daily feed-out rate should first be reviewed.
Total losses are what ultimately matter
The effect of a silage additive should not be assessed only on the basis of individual values measured while the silo remains sealed. A process may cause small additional losses during fermentation while reducing losses after opening through improved aerobic stability.
The entire process chain—from harvesting to feeding—must therefore be considered. The objective is not the lowest individual measurement, but the lowest possible overall losses combined with stable, hygienically sound silage.
Conclusion: analyse first, then select
Silage additives are not a universal safeguard against errors in forage conservation. When properly selected and correctly applied, however, they can be an important tool for supporting fermentation, limiting undesirable microorganisms or improving aerobic stability.
Selection should be based on forage type, dry matter content, contamination risk, compactability, intended storage period, silo type and subsequent feed-out rate. These factors determine the required mode of action and, in the next step, the appropriate biological or chemical solution.
AGRO‑NEX® supports farmers and agricultural contractors in assessing their starting conditions and selecting a suitable application concept.
Technical notice: This article provides general technical guidance and does not replace farm-specific advice concerning feeding, animal health or individual product use. Only authorised additives may be used, strictly in accordance with their labelling and the manufacturer’s instructions. No particular silage quality, storage stability or economic outcome can be guaranteed.
Further technical information: