Overheating Index
The Overheating Index provides a snapshot of the silage’s susceptibility to aerobic spoilage (heating) once exposed to air. A high sensitivity allows for early preventive actions to minimise feed-out losses and maintain feed quality. It also guides management improvements for future silage production.
Heating results from microbial activity, primarily yeasts, once oxygen is introduced (e.g., during feed-out). A temperature difference of more than 10°C between the silage and ambient air indicates spoilage.
Consequences of Heating
Heating can lead to daily losses of up to 3.5% dry matter and 15 VEM (Dutch net energy unit) per kg of dry matter. Over several days, these losses can exceed 10%. Reduced intake and even complete spoilage due to mould growth are additional risks.
Interpreting the Overheating Index
The index reflects how prone the silage is to spoilage upon exposure. Scores below 20 indicate low risk; scores above 50 indicate high risk.
Management Recommendations
- Feed more sensitive silage during winter
- Adjust feed-out rate or clamp height
- Use propionic acid on cutting faces
- Apply extra weights to improve clamp sealing
Future harvest tips
- Chop finer
- Increase compaction capacity
- Use additives (inhibitors or preservatives)