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Best practice – Ensiling maize

Advice from our specialist Advice from our specialist12-9-2019

Maize silage has plenty of starch available for the fermentation and has a low buffering, so should be easy to ferment. However it is higher dry matter than most grass silages and can have a longer chop length so is more difficult to consolidate in the clamp. This means there is more air in the clamp and greater risk from yeast and mould spoilage.

A maize crop is at greater risk than other forages due to the time of year it is harvested with yeast and mould growth on the standing crop.

Afbeelding: Untitled-2
Maize being transferred into the clamp


  • Fill the clamp quickly
  • Apply a suitable silage additive to improve aerobic stability and reduce dry matter losses.
  • Consolidate well. Roll continuously and keep the front face pushed up.
  • Seal completely for rapid, anaerobic fermentation.
  • Weigh down with tyres, bales or weights.

Silages vary in two ways. Firstly how easily they ferment which is determined by the amount of starch or sugar available plus their buffering capacity and secondly how easily they heat up in the presence of air also called aerobic spoilage.

Using an Additive

Reasons to treat forage maize with a silage additive:

  • Reduce DM losses during fermentation & storage
  • Reduce losses & waste after opening
  • Increase Milk Yield or Live Weight Gain

The risk at feed-out is greater during warm weather with higher ambient temperatures or if the removal across the face is slow. A narrow face can help reduce waste if the amount used in the diet is low and moving from left to right in a consistent way so that the oldest exposed material is used first will also help.

Using a silage additive can improve aerobic stability and reduce DM losses by up to 50%, however choosing the right additive is important to be most effective. Yeast and mould can tolerate lactic acid so a different type of fermentation which produces propionic acid and acetic acid is required to stabilise maize silage.

Energy losses from maize silage of 20-24% are typical with 16% from feed-out, face and fermentation DM losses. Silage clamps mainly heat at the top and shoulders where compaction is less, which is often shown as a 10 degree difference in temperature between the top and bottom of the clamp.

It may take 3 days for silage to heat up when exposed to air during the summer months or 5-6 days in the winter, however using a silage additive can increase this time by an extra 2-4 days allowing transition across the face before spoilage occurs.

Situations where silage additives may help maintain feed quality.

Situation Comment
>35% DM at harvest Dry maize is difficult to consolidate

Long-chop length (>20mm)

Long-chop maize is difficult to consolidate

Feeding out during hot weather

Warmer maize is more likely to deteriorate

Wide clamp face/slow feeding out rate

Maize left exposed to the air for a long time is more likely to deteriorate

Fast clamping/insufficient consolidation possible

Poorly compacted maize will have significant oxygen levels which can result in aerobic spoilage

Aerobic spoilage experienced in the past

An additive may prevent this, but should not be a substitute for poor management pre-ensiling


The digestibility and starch content of maize silage improves with time in the clamp. Ideally maize should be left for at least a month before feeding to allow pH and feed quality to stabilise.

For further information on maize, please contact your local ForFarmers Forage Specialist or call us on: 0330 678 1200