Overheating is a microbial degradation process. In silage, various anaerobic microbes that are activated by the presence of oxygen, especially yeast varieties, are present. This is the case when silage is opened. Overheating occurs when the difference between the temperature of the silage and the outside temperature is more than 10°C. Sensitivity to overheating is related to several factors, such as the acid content (pH), acid pattern and dry matter content. Overheating affects the preservation and palatability of the silage.
Overheating in silage can cost an average of 3.5% of dry matter and 15 Feed Unit Milk of energy per kilogram of dry matter in the silage per day. Because open silage is always exposed to overheating for two to three days, the loss in feed value quickly rises to 10%. This does not include a reduction in the feed intake or, in the worst case, the upset of an entire silage due to mold.
The overheating sensitivity score indicates how sensitive silage is to heat once opened. An overheating sensitivity of up to 20 points indicates that the silage is not sensitive to overheating, while an overheating sensitivity of over 50 points indicates that the silage is very sensitive to overheating. The overheating sensitivity index is determined by a Forage Manager.
Insight into the behavior of silage at the time of feeding to reduce future silage loss:
- In case of multiple silages: if possible, feed the silage with the highest overheating sensitivity in winter and with the least overheating sensitivity in summer.
- Increase/decrease feed rate by increasing/decreasing the amount of other products in the ration or decrease the height of the silage by lengthening it
- Use propionic acid to spray the cutting surface during ensilage (to prevent overheating)
- Use extra covering materials (sand / bags of gravel, etc.) to keep pressure on the silage and above the cutting surface
Towards the next harvest:
- At next harvest, chop finer
- At the next ensilage moment, arrange more driving capacity (yourself or via a contractor)
- Add a heating inhibitor and/or preservative during or after chopping at the next harvest.