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Silage management

Course: Silage Management | Last Updates: 27th May 2016

David Davies
Biography >>

Output from UK grass-based livestock production is valued at more than £8bn, representing more than 60% of the total agricultural output of the UK.
While grass is undoubtedly the cheapest source of feed on farm, ranging from £30-50/t dry matter (DM), silage is still the cheapest winter feeding option at £100-120/t DM. Attention to detail during silage making will result in silage with better feed value produced at a cheaper cost. The old haymakers’ saying “good hay is cheaper to make than bad hay” holds even truer with silage.
Silage making can be split into three distinct areas (figure 1). To make top-quality silage all of the points indicated are equally important and failure to adhere to any will result in poorer nutritive value.

Avoiding spoilage before and during harvest

The ideal silage is formed by the action of the good lactic acid bacteria that either occur naturally on the crop or are added when using an inoculant. But on the crop there is already a huge population of other micro-organisms that, depending on forage management practices, can outnumber the good bacteria by 1,000 to one.
To ensure the good bacteria have a fighting chance a few important rules need to be followed:

  • Make the last slurry application is at least eight weeks before cutting, unless injecting, in which case two weeks are sufficient. Slurry contains many millions of bad bugs that can survive on the sward for a number of weeks.
  • Apply sufficient nitrogen for the crops’ needs. Excess nitrate in the sward is more likely to result in silage with high ammonia and butyric acid concentrations.
  • Roll to remove soil contamination from molehills, etc.
  • Cut to leave 2.5-3in stubble. This will minimise soil contamination and ensure a quicker grass regrowth.
  • Wilt for maximum 24 hours for grass and 48 hours for legumes such as red clover. Extended wilting times can result in a 1,000 times increase in the level of aerobic spoilage micro-organisms such as yeasts and moulds.


The ideal date of cutting will vary from farm to farm depending on factors such as grass varieties used, height above sea level and latitude. But it will also vary from year to year on the same farm depending on the season.
It is important when producing silage intended for productive animals – be they dairy cows, beef or sheep – to aim for 67-70D. This is equivalent to 50% ear emergence. Research at IBERS, where the same grass was ensiled in three different ways, is shown in table 1 (below).

Table 1: Milk production from grass silage
Good practice Poor practice Mature crop
Dry Matter (%) 24.3 22.6 24.8
pH 3.9 3.9 4.1
Ammonia-N (g/kg N) 11.7 13.1 11.5
ME (MJ/kg DM) 12.6 12.7 10.4
Crude Protein (%) 19 19.6 13.5
Intake (kg/d) 13 6 12.5
Milk Yield (litres/d) 24 21 19

The research aimed to show the effect of different management practices on silage quality and, ultimately, animal performance. Grass was cut at the ideal time with an ME of 12.6 MJ/kg DM and ensiled in a clamp using good or poor practices. A third treatment delayed cutting for about two weeks until the ME had dropped two units to 10.4 MJ/kg DM.
On feeding, cows fed silage made from grass cut at an ideal stage and ensiled using good practice gave five litres more milk a day than cows fed silage made from mature grass. So maximising grass quality by cutting at the optimum maturity can result in a big difference in milk yield and thus profitability.


We recommend a rapid wilt and research conducted in Germany has shown that with the pores on the underside of the leaf open, water loss is 100 litres/t/hour, but when they close it drops to 20 litres/t/hour.
The pores only stay open for about two hours after cutting. So to achieve this it is important to spread the crop as quickly as possible once cut, over as wide an area as possible. An IBERS trial investigated the differences in sward drying times using three different treatments. These were mower conditioner with spreading (Mo/Co & tedding), mower conditioner without spreading (Mo/Co) or a Vicon high performance conditioner (HPC). Results are shown in Figure 2 and it is clear that the fastest rate of drying was achieved with the HPC, while tedding the crop speeded up the drying process over not tedding.

Silage management

The importance of good silage management can be seen from the results in table 1. The grass was harvested at the same time for the good and poor management practices, with differences in how the grass was handled between harvesting and ensiling. These differences resulted in a loss of three litres a day per cow representing more than £160 (based on a milk price of 29.5ppl and a 180 day winter) over a winter feeding period. The differences between good and poor practice were simply the way the grass was managed between forage harvesting and sealing the clamp. The well managed system had a good additive applied at the correct application rate. The grass was compacted well in small even layers and the silage clamp was sealed well immediately after the clamp was filled. The poor management had no additive, poor and uneven compaction and sealing was done slowly without sufficient top weight placed on the clamp after sealing.
Management of big bale silage also affects forage quality and the costs associated with poor bale management will be similar to those associated with clamp silage.

Bale wrapping and stacking

There are a few quick and easy rules to follow to ensure good big-bale silage production.

  • Ensure wrapper is set up to apply the correct number of layers at the right % stretch.
  • Use good quality film, green or black.
  • Wrap bales close to the stacking area.
  • Wrap within two hours of baling.
  • Apply a minimum of four layers of film to the whole bale, but use six layers for square bales, bales with dry matter over 40%, heavy chopped bales or those for stock sensitive to mould eg pregnant sheep and horses.
  • Only stack three high if the silage is 30% DM or greater.
  • Store more than 10m away from a watercourse on a surface that is free from sharp stones, etc.
  • Protect the bales from bird and vermin damage.

Table 2: Average spoilage per bale for different wrap combinations
The practical question of which colour of wrap to use is one that CEDAR has researched, together with Dow Europe. In a recent comprehensive experiment, grass was wrapped with either four or six layers of either green or black film. The amount of spoilage was recorded on opening the different treated bales and showed that there was less wasted with a combination of four layers of green film, than any of the others. Green film is proven to keep the surface of the bale cooler which reduces the permeability of the wrap hence reducing the growth of spoilage organisms in the bale and retaining valuable nutrients.

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