Mid-Winter Forage Review

Mid-Winter Forage Review


If the clamp is looking untidy & the face is uneven, it’s likely that it is allowing air to get in – the number one enemy to silage. Correcting an untidy face is a straightforward fix, with the use of a block cutter or shear grab to ensure minimum disturbance to the silage which will make a big difference to the existing crop.

Clean Silage face

If there is wastage present further into the clamp this may indicate poor fermentation, which is due to oxygen being present in the clamp at sealing and will need to be improved next season. Correct clamp consolidation is one of the most important factors when it comes to ensiling, as this removes all the existing air from within the crop, helping to make an anaerobic environment which improves the fermentation process. Using an oxygen barrier silage sheet will also be beneficial, as this stops entry of oxygen through the sheet & ensures there is no waste on the top and shoulders – the hardest areas of a clamp to compact. If there are darker layers of silage visible, this can indicate that excess nitrogen was present in the grass when it was cut, it is important to ensure that a long enough window is left between nitrogen application & cutting.


Good quality silage that has been well compacted should remain cool. If the silage feels warm to the touch, this is a sign of aerobic spoilage, which is caused when silage is exposed to oxygen & will worsen once the clamp is opened. To prevent heating next season, compaction & sealing are again key. Use of an oxygen barrier sheet has been proven to improve aerobic stability and prevent heating once the clamp has been opened by an additional two days, making the crop more palatable.

Clamp temperature


How does the clamped silage smell? If the crop has an unpleasant smell, it is likely a sign of poor fermentation. This will make the crop less palatable at feed out, and like heating up of silage, will cause even more of the nutritional value to be lost. When looking ahead to next season, ensure harvesting takes place at the correct moisture & stage of maturity. The clamp should be filled rapidly with effective compaction & then sheeted immediately afterward.

Well fermented silage means reduced losses of DM, resulting in more available high-quality feed, which will improve feed intake, milk production & ultimately profitability. Typically, it takes between 10 days – 3 weeks for adequate fermentation, so silage should not be fed until after this process is complete.

Cows eating silage


Wet, slimy silage can be another indicator that there was excess nitrogen present at harvest. It can also be due to low sugars & poor fermentation which allows the negative bacteria so break down the crop in the clamp. It is important to ensure the crop is cut at the correct timing, ideally in the afternoon/evening when sugar levels have increased, and grass has been wilted to more than 28% DM.

If the crop is too fibrous, it’s likely that it was cut too late and will contain excess stem material. This is typical if cutting was delayed with the aim of achieving extra bulk. The optimum time for quality & high yielding silage is to cut just before the grass starts heading, if the crop is cut after heading, the digestibility falls by approx. 0.5% daily.

checking silage

Dry Matter

The DM % is the amount of silage left over after the water has been removed, usually the higher the DM, the higher the potential intake of silage – however if silage is too dry, this can cause heating & mould. If the DM is too high or low, usually the wilting technique needs to be reassessed ahead of next season. Rapidly wilting to 28-32% DM is the ideal target to minimise in field losses and reduce the risk of effluent once clamped. Correct sealing of the clamp can help to ensure no additional oxygen can enter once sealed, along with the use of an appropriate additive, which makes clamp conditions anaerobic faster and thus speeds up the fermentation process.