Eight-point plan to making better quality silage

Producers could be shooting themselves in the foot by failing to adhere to the basics of silage making. Aly Balsom provides some step-by-step points to making the best silage

Failure to get the most from home produced forage this season could mean livestock farmers are hit with an even bigger feed bill than necessary.

According to grassland experts, rising input costs mean there are even more benefits to be had from making top quality grass silage this year.

Piers Badnell, DairyCo extension officer, says growing higher quality grass silage can reduce the amount of bought-in concentrate significantly.

“Producing a grass silage with an ME of 11.7MJ/kg DM versus an ME of 10-10.5 MJ/kg DM will mean that for every 10kg of DMI, you are likely to see a three-litre increase in milk production.”

But to reap the benefits it is important farmers adhere to all the steps involved in silage making:

Selecting fields for silage:

• Close-up all grazing areas with covers of more than 3000kg DM/ha for silage

• Start monitoring silage fields for cutting as soon as fields are shut-up

• Avoid cutting fields or grass areas where soil contamination is a problem – as soon as you put soil through the harvester, it will ruin the whole clamp

• Think about controlling moles now

• Consider using an additive when ensiling soil contaminated silage is unavoidable (see box)

• For an optimum quality silage at 70% D value and 11 MJ/kg DM ME, grass should be cut just prior to ear emergence

• Ear emergence can be assessed by splitting the stem with a thumb nail

• When you have concerns over residual N, send off grass for analysis – when N levels are too high, fermentation will be slower and silage ammonia levels will be high, resulting in reduced intakes

Silage additives

There could be a higher level of dead material in the bottom of the sward this season following the long winter. As a result, using a silage additive may be worth considering, says consultant Dave Davies, Silage Solutions.

“Many farmers will be on top of this problem, but it is a potential issue for some.

“When dead material is an issue, aerobic stability may be compromised, so consider using a Lactobacillus and benzoate sorbate or sulphate salt type additives. The bugs will help with fermentation, while the salts inhibit the yeasts and moulds.”

An acid type additive to control mould and yeast growth can also be used when soil contamination is a concern.

Silage enhancers can also be used to promote protein degradability, says Douglas Green of Douglas Green Consulting. “With the cost of supplementary protein so high, the case to use these additives can be high. But remember inoculants will make good silage better, not bad silage, good.”

When to cut?

• When the D value is correct and N levels low, grass should be cut at the first spell of good weather

• Cutting on a bright day is ideal. This will increase the sugar content of the grass, which means sugar is more likely to be retained. Sunshine will also promote a more rapid wilt, reducing the amount of water ensiled

• It is imperative grass is dry when cut – cutting when wet will mean a longer wilt time and a reduction in nutrients

• Cutting late in the day is more preferable than starting at 9am when dew may still be a problem.

“When you think grass is ready a week before you would ideally cut and the weather is OK – go in and cut,” says Dr Davies.

“When you wait a week, quantity may be higher, but quality will be reduced.”

It is better to cut earlier than usual, agrees Mr Badnell. “This may mean yields are lower, but good re-growth will mean second cut yields will be higher.”

Mowing and wilting

• The mower should be set at a minimum height of 2.5in. This can be increased to up to 4in on new leys

• To speed up the wilting process, the cut crop should be spread out over 100% of the field straight after cutting

• The stomata in the grass are only open for a few hours post cutting, so it’s important to maximise water loss during this period

• A rapid wilt prevents excessive sugar and protein losses – ideally grass should not be left for longer than 24 hours

• Aim for a target DM of 30%

• When grass is ensiled too wet, silage will be too acidic or ammonia levels will rise creating an unpalatable feed. Effluent is also likely when dry matter is less than 25%

• When grass is too dry, consolidation will be a problem and secondary fermentation is likely at feed out.


• Rake up as close to harvesting as possible

• Set up the rake on solid ground and check the tines do not touch the ground when turning

• Ensure the person raking knows what they are doing – compromising here will only compromise quality.


• Ideal chop length will promote good consolidation in the clamp, but provide enough fibre for the cow

• Chop length should be set at one inch for grass with a DM of 30%

• When grass is wetter (20% DM), consider a chop length of 2in

• High DM grasses will be harder to consolidate so a shorter cut may be appropriate

• First cut is a good opportunity to look critically at how productive a sward is and assess whether a summer re-seed is needed.

Clamp management:

Filling of the clamp is where the biggest problems lie in terms of grass silage making.

Sally Tuer, consultant for the Dairy Group, says the key aim is to make the clamp as air tight as possible. “It is important there is no cracked concrete on the floors or walls of the clamp. All effluent should also be collected to prevent environmental contamination.”

• Clean the clamp thoroughly

• Provide adequate overhang on the side sheet as it will gradually disappear as the clamp is filled

• Consolidation is where the biggest problem lays – ensure grass is spread in even layers of no more than six to nine inches and rolled consistently

• When silage layers are too thick, pockets of air will be formed, slowing fermentation and increasing yeast and mould growth. Silage is also more likely to heat up when the clamp is opened

• Use two tractors – one rolling and one buck raking

• In a wet season, it is worth sacrificing grass to drive over and clean the tractor wheels before entering the clamp to reduce soil contamination

• 15% wastage is likely when carrying out best practice, but this loss will double when you are not getting things right

Sheeting up:

• The aim should be to make an envelope with the side sheet so that any water running off the top of the clamp runs down the side and not into the silage

• When not filling a clamp in one day, do not roll until another load has been delivered the following day, otherwise you will introduce air into the clamp

• Double sheeting with silage sheets is recommendable to ensure all air is expelled – use a new sheet first and then last year’s sheet on top

• When using weighted silage sheets as an alternative to tyres, a slight dome is needed on the silage clamp to ensure adequate “pull down”

• On inside clamps, straw bales are a better option for weighting down silage sheeting as they are heavier than tyres

• Cling film-type silage sheets are becoming widely used. These thin plastic sheets cling down on the top of the silage, reducing air pockets and reducing spoilage; a black silage sheet will still be needed on top.

Low permeability, clear polythene sheets dramatically reduce visible waste and improve silage quality, says consultant Hefin Richards, ProFeed Nutrition. “With the cost of silage making and bought in feed, any steps that can be taken to improve quality should be taken – using cling film-type silage sheets is a no brainer.”

* To read more about weighted silage covers and silage clamp tyre management, visit www.fwi.co.uk/tyrewire

Feed out

• Leave a minimum of 3-6 weeks before feeding out or analysing fresh silage – opening too soon will affect fermentation, increase wastage and produce a more variable feed

Working with the contractor

The farmers that produce the best quality silage are generally the ones that stand by the clamp during silage making, says Dr Davies.

“Make sure you are involved in the process and the best place to do this is at the clamp. You can then monitor chop length and check that rolling is being carried out OK.

“And don’t be afraid to say slow down – after all, it’s your silage.”