The basis of all good silage: air exclusion and the fermentation process
The quality of silage is determined as early as the ensiling stage. The aim is to preserve the crop as quickly as possible and permanently in an oxygen-free environment. Only under oxygen-free conditions can the desired lactic acid bacteria begin their work and set the natural fermentation process in motion.
During fermentation, the sugars naturally present in the plant material are converted into lactic acid. This lowers the pH value and preserves the silage. For this process to be successful, even distribution of the crop and thorough compaction are crucial. Modern silage spreaders ensure an even layer formation in the mobile silo, whilst high-performance silage rollers displace the trapped air from the forage.
The less oxygen remains in the silo, the faster and more reliably the desired lactic acid fermentation takes place. The silo must then be sealed airtight. Only in this way is oxygen permanently excluded and can the silage develop its stability.
Once sealed, the silage needs sufficient time to ferment. In practice, a drive-in silo should remain sealed for at least six to eight weeks before the first feed is removed. Only then is fermentation largely complete and the silage reaches its desired feed quality.
If the work has been carried out properly, the result is high-quality forage with a high energy density and good storability. Compaction within the silage pile forms the basis for silage that remains stable in the long term. This structure should, as far as possible, be maintained even after the silo has been opened.
Summer challenges when removing silage
Particularly during the summer months, the risk of quality loss increases significantly. High outside temperatures, intense sunlight and warm nights create ideal conditions for undesirable heating processes. Whilst in the past the night-time hours at least provided some noticeable cooling, temperatures today often remain at a high level round the clock. The result: the silage pile is under constant thermal stress. This development is no longer an exception. Summers are getting hotter, heatwaves are lasting longer and extreme weather conditions are occurring more frequently. For farms, this means that the demands placed on stable silage are constantly increasing. This is because with every additional degree of temperature, the risk increases that yeasts and other microorganisms will become active as soon as oxygen enters the silage.
This is precisely why the correct removal technique becomes enormously important during the summer months. A clean and sealed cut surface plays a central role here, as it helps to keep warm air away from the remaining silage pile and limit the ingress of oxygen. It is important that the compaction of the remaining silage pile is maintained and that as little oxygen as possible is allowed to penetrate.
If the silage is torn open, ripped out or heavily loosened during removal, numerous entry points for air are created. Oxygen and heat can thus penetrate significantly deeper into the silage pile and trigger biological processes there that remain invisible at first.
Clean removal that preserves the structure therefore not only protects the current feed supply at the cut surface. It also plays a key role in protecting the entire remaining silage mass from heating, quality loss and post-fermentation – particularly when the summer heat puts the silage under additional strain.
Warm summer air promotes abnormal fermentation in the silage pile
As long as the silage remains airtight, the acids formed during fermentation ensure stable preservation conditions. However, if warm air penetrates the silage pile, yeasts and other undesirable microorganisms become active again.
Initially, yeasts begin to break down sugars and valuable lactic acid. This process generates heat. The rising temperature, in turn, accelerates the activity of the microorganisms – a cycle that can intensify rapidly, particularly on hot summer days.
This process is known as post-heating.
If the supply of oxygen continues, this often leads to a process of spoilage. As the lactic acid is broken down, the pH of the silage rises again. The preservative effect diminishes and conditions for undesirable microorganisms become increasingly favourable.
If the silage pile is further loosened by improper removal, cracks, voids and entry points for warm air are created. As a result, oxygen and heat penetrate deeper into the compacted silage. The warming is then no longer confined to the cut surface but can gradually spread into the silage pile.
As the temperature rises, moulds, putrefactive bacteria and other pathogens causing abnormal fermentation find increasingly favourable living conditions. The silage loses its stability and valuable nutrients are lost.
What is particularly insidious is that these processes often remain invisible at first. Whilst the cut surface may still appear unremarkable on the outside, post-heating and spoilage fermentation may already be developing inside the silage pile. Particularly during hot summer periods, it is therefore worth consistently minimising air ingress by ensuring clean and structure-preserving removal.
The consequences are manifold:
Breakdown of valuable nutrients
Loss of energy content
Reduced feed quality
Reduced palatability
Increased mould contamination
Declining feed intake by the animals
Economic consequences of post-harvest heating
Any form of post-harvest heating causes losses. The energy and nutrients that were originally harvested, transported, compacted and stored at great expense are no longer fully available to the animals.
Part of the feed loses quality, whilst another part may even have to be discarded. Silage contaminated with mould or that has become excessively warm is no longer suitable for safe feeding.
This results in direct costs. Heating leads to a loss of dry matter and valuable nutrients, which increases feed requirements and may necessitate additional replacement feed. At the same time, the workload increases, whilst potential losses in animal performance further exacerbate the economic consequences. Against a backdrop of rising production costs, any measure that maintains the stability of the silage and reduces losses therefore becomes increasingly important.
A key starting point lies directly at the cut surface – as this determines how well the remaining silage is protected from oxygen.
– Henryk Schultz, Agrargenossenschaft Oberes Elbtal Reinhardtsdorf e.G.
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Silage grab bucket or cutting system – a crucial difference
When removing silage with a silage grab bucket, the silage is often not cleanly separated but torn out of the silage pile. This loosens the compacted layers of forage and disrupts the structure of the remaining silage pile. The effects are often not limited to the quantity removed directly. The pulling action creates cracks, voids and loose areas through which oxygen can penetrate deep into the silage pile.
Particularly during the summer months, this additional hot oxygen creates ideal conditions for yeasts and other aerobic microorganisms. They begin to metabolise the readily available nutrients in the silage, thereby generating heat. The result is rising temperatures in the cut area, declining forage quality and increased nutrient losses. If this process is not interrupted, the heating can gradually spread further into the silage pile.
Cutting systems therefore take a fundamentally different approach. Shear grabs and cutting shovels separate the silage from the silage pile with a clean cut, rather than tearing it out.
Silage grab bucket
Tears the forage out of the silage pile and loosens its structure
Creates cracks and voids through which oxygen can penetrate deeply
Higher risk of spoilage and nutrient losses
Shear bucket and shear grab
Cuts the forage cleanly and preserves the compact structure
Leaves a smooth surface and prevents oxygen ingress
Greater silage stability and better preservation of forage quality
The first crucial factor is the stable, welded cutting edge without any protruding material. This allows the shear bucket or cutting tongs to glide smoothly through the silage pile without snagging on the silage or pushing material ahead of them. The forage is cleanly separated and not loosened.
The second factor is the high cutting force. Combined with the sharp cutting edge, this enables a particularly even cut and ensures perfect gliding through the silage mass. The cutting edge penetrates the silage mass in a controlled manner, rather than displacing or tearing out the forage.
The third factor is the cutting geometry, which is specifically designed for silage. It promotes a consistent cut across the entire working width and ensures that the forage is cleanly severed. This results in a cut surface that is as smooth and even as possible, with fewer points of entry for oxygen.
Thanks to the interplay of these three characteristics, the cutting edge penetrates the compacted silage pile evenly and cuts the forage cleanly. The surrounding structure remains largely undisturbed and is neither torn open nor loosened. This has a direct impact on silage stability. At the same time, the risk of spoilage and nutrient loss is reduced. The remaining silage retains its quality for longer and is available to the animals in a more consistent form. Every clean withdrawal therefore protects not only the amount of feed currently required, but also the entire remaining feed supply in the silo.
The cut surface as a protective shield for the silage block
The cut surface is the most sensitive part of an open mobile silo. However, its role is not merely to look clean. Rather, it acts as a protective shield for the silage mass behind it – particularly on hot summer days. Measurements show that, when silage is removed using shear grabs or a shear bucket, the cut surface often reaches higher temperatures at the surface than when removed with a silage grab bucket. However, what matters is not the temperature directly at the cut surface, but how far this heat can penetrate into the silo mass. Thanks to the smooth and sealed cut surface created by shear grabs and shear buckets, the high temperatures are, in a sense, contained at the cut surface. The compaction of the silo mass is maintained, and the heat has significantly fewer opportunities to penetrate into deeper layers. Whilst the surface may be warmer, the temperatures inside the silage pile remain considerably more stable.
The situation is different when removing silage with a Silage grab bucket. Tearing open and loosening the silage creates numerous cavities and pathways for heat to enter. As a result, the temperature directly at the cut surface often appears lower; at the same time, however, the heat can penetrate much deeper into the silage pile. Particularly at depths of 40 cm to 100 cm, significantly higher temperatures are frequently measured than with a clean cut surface. Ideally, the silage should be 15 °C at a depth of 40 cm. The main concern here is significant temperature differences between the cut surface and deeper layers. Fluctuations of more than 5 °C pose a high risk of heating processes and can jeopardise the stability of the entire silage pile. The cut surface therefore protects not only the currently visible area, but the entire remaining feed supply behind it.
Comparison of the cutting surface: Silage grab bucket vs shear grab
A smooth cut surface in the grass silage prevents the ingress of warm summer air
The cut surface produced by the shear grab and shear bucket ensures a cool silage pile
Actively counteracting post-fermentation heating in summer
However, once the silo has been opened, it is primarily the removal technique that determines how well the silage retains its quality. In summer in particular, high temperatures can further exacerbate the effects of oxygen ingress and increase the risk of post-heating. The cut surface plays a key role here. It forms the boundary between the ambient air and the compacted silage mass. If the silage is torn out with a Silage grab bucket, the structure is often loosened and oxygen can penetrate deeper into the silage mass. This results in increased risks of post-fermentation heating, nutrient losses and a decline in forage quality.
Switching to a shear bucket or shear grab helps to prevent these losses. Both systems cut the silage cleanly from the silage pile, maintain the compaction and leave a smooth cut surface. This reduces air ingress and improves the stability of the remaining silage. As well as safeguarding forage quality, gentle removal also offers economic benefits. Less post-fermentation means lower losses of energy and nutrients, better feed intake and more efficient utilisation of the stored feed.
Switching from a silage grab bucket to a shear bucket or shear grab is an important step towards improving silage quality and economic efficiency. By maintaining compaction within the silage pile and minimising oxygen ingress, you protect your feed supply and reduce losses in the long term.
