2nd May 2023

Our top three tips to maximise silage quality this year

Grass is the cheapest livestock feedstuff there is and producing quality silage can be a valuable way to help maximise profit while optimising nutritional intake.  

The drought of 2022 impacted both the quantity and quality of the grass silage produced across the UK. According to a survey conducted by Ecosyl:

  • 74% of the dairy farmers questioned, who make silage conventionally, reported that their grass silage crop had declined due to the drought
  • 35% said that the quality of grass was poorer than in previous years
  • Most respondents were planning to improve the quality of their silage this year
  • 79% stated that high feed costs are pushing the move towards a greater reliance on quality silage

Here are our top 3 tips to help improve your silage quality this year and reduce wastage. 

1. Optimise grass cutting times 

Cutting time can have a significant impact on silage quality.  The timing of the grass cuttings will depend on the livestock  you’re planning to feed the silage to. To help determine this, it’s recommended to start taking samples three weeks before last year’s cutting date to get an insight into the D-value (a measure of digestibility), nitrate level, crude protein and natural detergent fibre (NDF).

Grass for silage should be cut when the NDF value is between 38% and 42%. Arise of 5% in NDF can lead to a reduction in metabolizable energy of 1.6 MJ per Kg/DM. The target percentage of dry matter at cutting should be 28-32% for clamp silage and 35-45% for bale silage. This will speed up the wilting time by reducing the amount of water needing to be lost and reduce effluent lost during the ensiling process. Silage effluent should be stored in accordance with the Defra’s silage, slurry and agricultural fuel oil (SSAFO) regulations as it’s 200x more polluting than raw sewage. 

Grass growth indicators

  • As the grass starts to grow more stems and heads, the yield may increase but  digestibility tends to decrease
  • As the grass starts to produce flowering stems, the D-value reduces by 0.5 units every day. 
  • If the grass has bolted and started to produce woodier stems, the silage produced can still be used, but will be of lower quality. 

As a general rule, the table below highlights the values you should aim for when testing silage ahead of cutting, dependant on the end use.









% ear emergence




Energy (MJ/kg DM) 




Crude protein %





Finishing cattle and ewes carrying two or more lambs

Autumn calving  sucklers, ewes carrying singles

Dry cows, spring calving sucklers

Adapted from AHBD “Making grass silage for Better Returns

2. Ensure correct consolidation of the silage clamp

As the fermentation of grass to make silage happens under anaerobic conditions, ‘squeezing’ the air out of the grass as you put it into the clamp is essential. If your grass has a DM of 30%, you should aim for a density of 250kg/DM/m3.

Make sure trailers of freshly cut grass arriving at the clamp don’t come so quickly that there isn’t enough time to spread the grass out between loads by using smaller trailer loads or waiting until adequate compaction is reached before adding another load. 

Even the heaviest of tractors can only compress the top 15cm of silage at a time, so compacting thinner layers will lead to better-quality silage due to more consistent compaction. 

The edges of the clamp are often the hardest to consolidate effectively, so pay particular attention to them with the compactor. Use a compactor that has an equal width to the tractor so that there aren’t ‘hot spots’ under the tractor wheel. 

3. Seal the clamp with Sila-Cover® 300

Dry matter losses can be as high as 25% in a clamp, due to poor consolidation and incorrect sheeting, creating unnecessary wastage. Creating an airtight seal is key to enabling fermentation. Keeping the air out during fermentation, and until feed out, reduces spoilage and prevents contamination from the elements and pests. 

When preparing the clamp:

  1. Add side sheets to the edge of the clamp with a 1.5m overhang which can then be folded in
  2. Place a high-quality oxygen barrier over the side sheets and a top sheet over the top.
    1. The top sheet should be strong enough to withstand high winds while still being flexible enough to mould to the silage and maintain the airtight seal. 

Galebreaker’s Sila-Cover® is made from super-strong 300g/m2 polyethylene material with twice the tensile strength of knitted high-density polyethylene (HDPE) of the same weight. The close weave is impenetrable to birds and rodents. Sila-Cover® also moulds to the shape of the silage, ensuring a more oxygen tight seal. 

Lower levels of the clamp will have been compacted more by the tractor and weights of the layers on top, but the top can remain quite loose. Weighing down the top of the clamp guarantees consistent fermentation throughout the entire crop. 

Galebreaker’s Sila-bags provide an alternative to using tyres to weigh the clamp down. Tyres can release harmful chemicals and shards of metal which can contaminate the silage and even cause death. Sila-bags are made from the same polyethylene as the Sila-Cover® with hooks that can securely attach them in place, even in high winds and on steep slopes.