Tama Assist From Field to Feed: What Happens Inside a Wrapped Bale?
A well made silage bale might look simple from the outside, but inside it is a carefully managed biological process. The quality of the feed months later depends on what happens in the first few hours and days after baling; and on how effectively air is kept out of the crop.
Understanding what’s going on inside a bale helps farmers and contractors make better decisions in the field, from crop moisture and baling density to the choice of netwrap and film.
As soon as grass is cut and baled, the plant cells and naturally occurring microorganisms begin to respire, using oxygen and producing heat.
For good silage, this aerobic phase needs to be as short as possible. Once oxygen is excluded, beneficial lactic acid bacteria begin to dominate, converting sugars into lactic acid. This lowers the pH and preserves the crop, locking in feed value.
If oxygen remains present for too long, less desirable microbes can multiply, leading to heating, mould growth, and dry-matter losses.
In simple terms:
Air present = spoilage risk
Air excluded quickly = stable, high quality silage
A dense, well formed bale contains less trapped air to begin with. But just as important is the shape of the bale surface, particularly with round bales.
If the surface is uneven, or if the edges are not properly supported, pockets of air can remain between the bale and the stretchfilm. These pockets can allow aerobic activity to continue locally, even when the rest of the bale is fermenting correctly.
This is why consistent bale formation and even coverage across the full width of the bale are so important.
Before stretch film is applied, the netwrap plays a key role in holding the bale’s shape.
Lower quality or poorly performing net can sometimes fail to cover the bale fully from edge to edge. This can leave what operators often refer to as “shoulders”; areas at the edges where the crop is less tightly contained.
These shoulders can:
- Make it harder for stretchfilm to seal tightly
- Increase the likelihood of air being trapped
- Raise the risk of mould developing at the bale edges causing more bale wastage and ultimately, increasing your baling costs
Edge-to-edge net coverage helps produce a smoother, more uniform bale surface, allowing the stretchfilm to perform as intended.
Once wrapping begins, the stretchfilm takes over as the primary barrier against oxygen.
Good wrapping achieves three key things:
- Excludes oxygen by sealing the bale
- Maintains pressure on the crop as it settles
- Protects against punctures and weather
The number of film layers, the overlap, and the condition of the bale surface all influence how effective this barrier will be.
Even small amounts of air ingress over time can allow yeast and mould to develop, particularly around the outer layers of the bale.
Once sealed, fermentation typically progresses through several stages:
- Initial respiration (first hours)
Plant cells and aerobic microbes consume remaining oxygen.
- Lactic acid fermentation (first days to weeks)
Beneficial bacteria convert sugars into lactic acid, reducing pH and stabilising the silage.
- Stable storage phase
If air has been successfully excluded, the bale remains stable for many months with minimal nutrient loss.
Problems generally arise when oxygen re-enters the bale, either through poor sealing, damage to the film, or uneven bale formation.
When silage quality is disappointing, the cause is often linked to one or more of the following:
- Crop baled too dry or too wet
- Low bale density
- Delays between baling and wrapping
- Insufficient film layers
- Air trapped due to uneven bale shape
- Film damage during handling or storage
Many of these factors are within the operator’s control, and small improvements can make a noticeable difference to feed quality.
Good fermentation preserves:
- Energy
- Protein
- Palatability
Poor fermentation can lead to:
- Dry-matter losses
- Heating and mould
- Reduced intake by livestock
Ultimately, every bale represents a significant investment in time, fuel, labour, and land. Protecting that investment depends on getting the details right; from mowing and baling to netwrap performance and wrapping technique.
A wrapped bale isn’t just stored grass, it’s a controlled fermentation system.
The faster oxygen is removed, the more stable the silage will be. Bale density, uniform shape, effective net coverage, and high quality stretchfilm all play a role in creating the right conditions from the moment the bale leaves the chamber.
Because in the end, what happens inside the bale determines what comes out at the feed face.
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