Dr. Ma. Estela Uriarte Archundia
Technical Advisor to synBios and Silostop
July 2026
Good Sealing Reduces Silage Heating
Ensiling is an anaerobic process for preserving forage. This means that, for the process to work effectively, it must take place in the absence of air.
If forage comes into contact with air, it begins to deteriorate (or "spoil"). As silage deteriorates, its temperature increases. Therefore, silage that is heating up is silage that is deteriorating. This has several negative consequences, including:
- Reduced nutritional value
- Growth of microorganisms or production of compounds that negatively affect livestock performance and health
- Significant economic losses
What is Aerobic Deterioration of Silage?
Because ensiling is an anaerobic process, exposure to atmospheric oxygen causes deterioration. This results not only in the loss of valuable nutrients but also in the production of volatile organic compounds that can negatively affect feed intake, milk production, and animal health.
Poor silo sealing allows air to enter and remain trapped within the forage for extended periods, resulting in considerable losses.
The presence of oxygen creates ideal conditions for undesirable microorganisms to grow, causing silage deterioration. In simple terms, air causes silage to spoil.
Aerobic deterioration is characterised by the heating of the forage.
Although aerobic deterioration is a complex process, it depends largely on whether microorganisms capable of causing deterioration survive or become established during the fermentation and storage phases.
If the populations of these spoilage microorganisms are high, aerobic stability will be short, meaning the silage will heat quickly.
The principal factors influencing aerobic deterioration include:
- Oxygen exposure (both the amount of oxygen and the length of exposure)
- The microbial populations present
- The type and quantity of available nutrients within the forage, particularly water-soluble sugars and organic acids
Of all the microorganisms present, yeasts are the organisms most closely associated with aerobic deterioration.
The Role of Yeasts
Yeast growth is promoted by oxygen.
Certain yeasts can use the lactic acid present in silage as an energy source.
The greater the number of these lactic acid-utilising yeasts, the faster silage begins to deteriorate and the greater the resulting nutrient losses.
Research has shown that silages containing more than:
5 log₁₀ CFU of yeast per gram of forage
(approximately 100,000 colony-forming units per gram)
are susceptible to aerobic deterioration, particularly when most of these yeasts are capable of utilising lactic acid.
How Can Good Sealing Reduce Aerobic Deterioration?
Effective sealing is essential to prevent oxygen entering the silo.
Good sealing is achieved by:
- Using correct sealing techniques, including 1.5 metres of overlap between sheets and around the perimeter of the clamp.
- Applying uniform weight across the entire surface.
- Sealing the silo immediately (within 24 hours) after compaction, or after completing each section.
- Using materials that provide an effective oxygen barrier.
Poor sealing allows oxygen to infiltrate the silo, causing aerobic deterioration, nutrient loss, and a reduction in forage quality.
Sealing within 24 hours is therefore critical for minimising oxygen ingress and reducing aerobic spoilage.
Effects of Delayed Sealing
Exposure to oxygen during filling and storage can delay fermentation.
This delayed fermentation allows undesirable microorganisms to survive and multiply, consuming valuable nutrients within the forage.
The document includes research showing the effect of sealing time on:
- Figure 1: Silage pH
- Figure 2: Lactic acid concentration
(Both adapted from Weiß et al., 2022.)
Yeasts and Dry Matter Losses
Many yeast species ferment sugars naturally present in forage, including:
- Glucose
- Maltose
- Sucrose
During this process they produce alcohols such as:
- Ethanol
- Propanol
These fermentation products are associated with:
- Higher dry matter losses
- Loss of valuable nutrients
- Formation of volatile compounds such as aldehydes and esters
The document includes:
- Figure 3: Effect of sealing time on lactic acid-utilising yeast populations (Uriarte, Bolsen & Brent, 2002)
- Figure 4: Effect of sealing time on ethanol production (Weiß et al., 2022)
These negative effects not only reduce forage quality but also increase losses and make the silage more susceptible to spoilage during feed-out.
Figure 5 shows that delayed sealing increases dry matter losses.
Oxygen Barrier Films Improve Aerobic Stability
Using oxygen barrier films reduces oxygen entering the silo and therefore reduces aerobic deterioration.
In other words, plastics that limit oxygen transmission improve aerobic stability by:
- Preventing or delaying yeast growth
- Reducing mould development
- Preventing silage heating
- Preserving nutrients
- Reducing dry matter losses
Figure 6 demonstrates that oxygen barrier films significantly reduce yeast and mould populations in the upper layers of maize silage compared with conventional polyethylene film.
(Adapted from Parra et al., 2021.)
What is Aerobic Stability?
Aerobic stability is the length of time silage remains without heating after being exposed to air.
If the silage does not heat:
- Nutrient losses are minimised.
- Nutritional value is maintained.
- Overall dry matter losses are reduced.
Figure 7 shows that maize silage covered with an oxygen barrier film has substantially greater aerobic stability than silage covered with standard polyethylene film.
(Adapted from Parra et al., 2021.)
Summary
The paper concludes that oxygen is the main cause of silage deterioration after sealing. Good management practices—including immediate sealing, proper overlap, even weighting, and the use of oxygen barrier films such as Silostop—significantly improve silage preservation by:
- Reducing oxygen infiltration
- Limiting yeast and mould growth
- Preventing heating
- Preserving nutrients
- Improving aerobic stability
- Reducing dry matter losses and economic losses
- Supporting better livestock performance through higher-quality forage
This is a technically sound review supported by published research and clearly explains why sealing quality and oxygen barrier technology are critical for preserving silage quality.