March 31st - 2021

Silage production Part 1

Producing good quality silage

Good quality silage is essential to achieve low-cost high quality milk, meat and biogas. As the forage grown on the farm is the cheapest and largest part of the ration maximising its potential is highly important. A few key areas we recommend you focus on are:

• Ensuring the crop in the field is not over-mature at the time of harvest and is of high metabolisable energy (ME) value, 11.5 MJ/kg dry matter (DM). For grass and legume silages, the crop is also high in crude protein CP, >15% of DM, see Table 1.

• Cutting grass as soon as possible when good weather is forecast. Delayed harvest of grass means a decrease in ME of 0.5 MJ/kg DM per week. Protein is also lower in mature grasses and legumes than in young, leafy crops. If you are using a contractor then ensure you are in regular communication and work together to make the most of the weather windows to suit.

• Minimising losses at all stages of silage making, particularly sealing the clamp. So often all the focus is on cutting, filling and good consolidation of the clamp that the sheeting is rushed and poorly done. It needs as much attention as the rest of the process to ensure that all the hard work and investment in the crop is protected to the maximum. An Oxygen Barrier film has to be a key element of the plan to ensure you minimise losses and reduce spoilage to enable most of the crop ensiled is available for feed out.

Target energy and protein concentrations of good quality silage

Typical losses of dry matter in field and silo

There is a huge range in loss of DM at each stage of the conservation process, depending on weather conditions and management of the silo.

Losses of dry matter between cutting and feed-out

Effect of weather on losses


• If rain occurs after cutting and pre-harvest, it increases loss in the field due to leaching of nutrients.

• Rain reduces the DM concentration of the crop at ensiling, which increases the extent of fermentation, with higher invisible loss of nutrients as carbon dioxide, and more visible loss as liquid effluent (leachate).

• Rain also increases the risk of soil contamination.


• Wind increases rate of water loss during wilting - a benefit, especially with high-yielding crops.

• Wind increases field losses - in high winds physical losses between harvester spout and trailer can increase.

• Wind increases the risk of poor covering of the silage surface due to difficulty of handling film during covering.


• Sunshine, combined with prolonged wilting of grasses and legumes, can result in high crop DM at ensiling. This increases the risk of poor consolidation and high nutrient losses in the initial aerobic phase of ensiling.

Effect of silo management on losses

Nutrient losses during respiration and fermentation are reduced by:

• Inoculation at harvest with live lactic acid bacteria (LAB).

• Good compaction of the ensiled crop during filling.

• Preventing oxygen ingress into the clamp.

Losses can be very high in uncovered clamps, especially in the top 50 cm. Surface spoilage and aerobic deterioration are reduced by:

• Covering the surface of the ensiled crop in the clamp with an Oxygen Barrier film as soon as possible. On large clamps or when the fill rate is slow, cover as the clamp is filled to reduce spoilage. A cling film which is designed to closely follow the contours of the crop and so eliminate air pockets is best practice and will significantly reduce surface spoilage.

• An additive designed to restrict the growth of yeasts and moulds.

Correct weight on top of the clamp once its covered is also vital. Random covering of old car tyres will not give the correct weight where needed and also adds to the risk of contaminating the silage with wire etc. The sustainable move towards gravel bags, offers a very effective solution to help seal the edges and joins of the sheets and covers, adding the right weight across the clamp when laid out in a grid effect has proven very successful.

Nutritional value of silage

Well-made high quality silage can supply up to 50% of the total daily ME required by the dairy cow, and up to 90% of the total daily ME required by beef cattle and sheep and is therefore a major feed cost item.

By delaying harvest for one week after the optimum stage of maturity (50% ear emergence for grasses, early bloom for lucerne), you can reduce DM intake by 10% which could be the equivalent to 1.5 litres of milk per day.

Also an extended delay in wilting lucerne can reduce protein concentration, this protein loss will then have to be made up with expensive bought in options.

Delayed harvest of whole-crop maize and whole-crop cereals is likely to reduce DM intake, digestibility and increase mycotoxin levels.

All the above show that good planning and timing of your harvest can have such an effect on the crop and its potential to feed your animals over the coming Winter.

Again our message is clear and simple, maximise your home grown forage by filling the clamp with a crop that is at its peak and protect it with a good quality Oxygen Barrier film and cover to ensure all the nutrients are available to feed.

For more detailed information click here

Tim Brewer