Silage harvesting season is well and truly underway, and while unfavorable weather conditions have slowed proceedings, farmers will be focusing on cutting, wilting, treating, picking up and ensiling silage over the coming weeks.

It is important to note that decisions revolving around these activities can have major implications for the quality of the resulting silage.

There are many benefits of feeding high-quality grass silage over the winter period. Firstly, silage is one of the most cost-effective ways to feed cows, and thus reducing the need for bought-in feed. As a result, profits can maximised by utilising one of the farm’s main assets – grass.

In addition, this high-quality forage has the potential to improve cow health and fertility. As part of Cut to Clamp – an initiative from Volac which aims to help farmers make consistently better silage – we take a look at all the important points to remember when harvesting a crop of silage.


The feeding value of silage is linked to the amount of leaf and stem present in the sward – an increase in the latter leads to a corresponding fall in quality.

Delaying cutting to boost yields has a negative impact on silage quality. The grass should be cut just before heading as it gives the balance of yield and quality; after heading, dry matter digestibility (DMD) declines by 0.5%/day.


Farmers should avoid cutting too low, as the base has the lowest digestibility and there is a risk of contamination with ‘bad’ microbes, which could hinder fermentation and cause aerobic spoilage (heating).

Another factor that needs to be considered is the sugar content of the grass. Grass sugars are highest on bright sunny days with cool nights.

A high sugar content is important to ensure silage crops preserve properly; if a crop is low in sugar, it can be resolved by wilting or adding an inoculant.

Farmers also need to keep an eye on the weather when planning to mow their silage, as it should only be done when weather conditions allow for harvesting and ensiling to be completed.

Mowing in wet or damp conditions increases the chances of soil contamination occurring, which can result in poor preservation and reduced feed quality.

When it comes to cutting height, it is recommended to mow dense swards to 5cm. But in open swards, this may need to be increased to 7.5-10cm to avoid the risk of soil contamination.


Wilting is an important step when making grass silage as it increases the dry matter (DM) percentage and reduces the quantity of effluent produced. Ideally, farmers should aim to wilt their silage to a DM of 28-32% – anything above this will have no benefit on animal performance.

Drying grass, through wilting, makes the sugars more concentrated in the grass, allowing the resulting silage to stabilise at a higher pH. This means that less acid or inoculant is required to preserve the crop.


In ideal conditions, farmers should aim to wilt the grass as quickly as possible to limit sugar losses post-cutting. The problem is, as soon as grass is cut, sugars start declining because they are being used up by the plant, since it is still living, and by undesirable bacteria.

This is important as approximately 6% of the sugars present in grass can be lost during a 24-36 hour wilting period. Therefore, the aim should be to wilt as rapidly as possible to an ideal target DM of 28-32%.

Harvesting and chop length

Harvesting or picking up the silage crop is important and there are a number of factors farmers need to bear in mind when completing this task. Such factors include: chop length; avoiding field losses; and making sure the entire process runs smoothly.

Farmers need to avoid the common pitfall of not paying enough attention to chop length, as using the optimum chop length is crucial when harvesting grass.

The optimum chop length has a big impact on how good a consolidation you can ultimately achieve in the clamp or pit.

The ideal chop length is to be driven by the DM percentage of the grass and, generally speaking, the drier it becomes the shorter the chop length that is required.

ken ring Kennedy Kennedys silage contractor

As a guide, if the grass is >30% DM, chop to 1.5-2.5cm – if being fed as part of a high-maize diet, this should be increased to ensure sufficient effective fibre in the diet to help improve consolidation.

If grass is at 20-30% DM, farmers should use a chop length of 2.5-5.0cm and if it’s <20% DM you may need to increase the chop length up to 10cm to reduce effluent and prevent clamp slippage.

Irish farmers and contractors often face a battle with the weather when picking up silage crops and the risk of rain may force some to overfill trailers.

However, overfilling trailers can result in losses and doing so can result in 1-2% of the grass crop being lost in the field. It may not seem like a lot, but on large acreages it can amount to a substantial amount of potential feed.

Furthermore, keeping the knives sharp and making necessary adjustments, if needed, can have a positive impact on the amount of fuel used during the harvesting stage.

Treating and fermentation

Silage is produced when beneficial bacteria ferment some of the sugars in grass to lactic acid. This ‘pickles’ the grass – preventing the growth of spoilage micro-organisms – and preserves nutrients.

An efficient fermentation requires air-free conditions within the clamp (pit). Farmers should also look at additive results, as well as reducing DM losses.

A quality bacterial additive can improve ME and D value and boost milk yield (by an average of 1.2L/cow/day in the case of lactobacillus plantarum MTD/1).

However, farmers should not leave preservation to chance; you don’t know if bacteria populations on grass are sufficient for an effective fermentation. When used correctly, a quality additive will supply one million ‘good’ bacteria per gram of forage.

The clamp

When it comes to ensiling, good consolidation is needed to squeeze out as much air as possible. For grass at 30% DM, aim for a target silage density of 250kg of DM/m³ (750kg fresh weight/m³).

If you trap too much air in the clamp when you ensile the grass, there is a risk of reducing fermentation quality and increase aerobic instability problems at feed-out.

Often, silage isn’t consolidated enough simply because trailers are arriving at the clamp too quickly and grass is not spread properly.

You can only really efficiently consolidate the top 15cm. So, layers should be even and no greater than this depth, before being compacted and the process repeated with the next layer.

For effective consolidation, consider using a compacter that equals the full width of the tractor, so that you’re not just consolidating beneath the tractor wheels.

Also, avoid over-filling the clamp. Once clamps are filled above the walls, density drops. Then, once consolidated, sealing the clamp will stop air / oxygen ingress, which is essential for fermentation and aerobic stability.

grass pit

Use side sheets and leave a good overlap with the top sheet of 1.0m, preferably 1.5m. Once the clamp is filled, the side sheet should be folded in, an oxygen barrier film placed on top and then a top sheet.

Always put as much weight on top of the clamp as possible. But, it is also important to pay attention to the ramp. If carbon dioxide is allowed to seep out of the bottom of the clamp (because it is heavier than air), it creates a vacuum, which sucks oxygen in.

So, as well as sheeting the rest of the clamp correctly, ensure there is at least 0.5m of extra silage sheet at the front of the clamp and weight it down well all around the edge.

Ecosyl lifts silage quality on Tipperary dairy farm

Different crops have different issues when it comes to making and feeding silage. The two main problems are achieving low, stable pH quickly and preventing aerobic spoilage (heating and moulding) – especially at feedout.

Generally, crops that are difficult to ferment are aerobically stable and vice versa. The Volac range of Ecosyl silage additives is effective in maintaining the nutritional quality of silage, whether clamp, big bale, maize or whole crop.

All of the silage inoculants have been thoroughly researched and tested, and are manufactured by Volac to the highest specification.

Co. Tipperary dairy farmer Michael Ryan is convinced of the benefits of Ecosyl additive in improving the quality of his silage.

Dairy farmer Michael Ryan

“I used Ecosyl once a number of years ago so I was aware of the benefits it could bring. Last year, I decided to try it again in order to improve preservation and quality.

“It worked great. The first and second-cut silage had an overall DMD of 74% and preservation was excellent with little or no wastage,” said Michael, who milks a herd of 80 cows at Killistafford, two miles from Cashel.

He used Ecosyl powder which last year was applied on the pit. This involved a lot of labour and was not as accurate as he would like.

Eco applicator

In late May, he installed a state-of-the-art eco-powder applicator on his forage wagon, which provides evidence of his commitment to using Ecosyl in this and future years.

The 80-cow herd is split into two-thirds spring and one-third autumn calving; the milk is supplied to Centenary Co-op.

Michael owns just 25ac of land around the milking parlour. He leases 111ac, half of which is approximately 0.5 miles away with the balance three miles away.


With such a limited grazing platform, zero-grazing is a big part of the feeding programme. Cows are zero-grazed indoors every night during the grazing season. He uses the forage wagon and has a front-mounted mower on the tractor.

With a third of the herd calving in the autumn, and such a limited grazing area, there is big emphasis on the volume of high-quality silage.

The first cut of 55ac was due to be harvested during the first week of June. A further 65ac will be closed for a second cut. All will be treated with Ecosyl; round bales will also be made from any surplus grass.


Michael has 28 replacement heifers ready for breeding and 20 replacement heifer calves are being fed this year. The rest of the calves, mainly beef crosses, were sold off the farm.

From next year, he will breed all cows to beef bulls and buy in-calf heifers. He plans to “increase a bit in cow numbers”.

He said breeding all cows to beef bulls and selling the calves will give him the extra cash-flow in spring when the payments on the leased land are due.

Michael Ryan with Rebecca O’Sullivan, Volac business manager. Silage treated with Ecosyl last year had a DMD of 74%

Ecosyl at a glance

  • Contains the unique MTD/1 strain of the lactic acid bacteria Lactobacillus plantarum, proven to bring about fast, efficient silage fermentation;
  • Guaranteed to deliver one million of these unique bacteria per gram of grass, leading to a rapid fall in the pH of the silage, thereby speeding up the fermentation process;
  • Backed by more independent research than any other silage additive;
  • Proven to lift digestibility, leading to increased dry matter intake and improved animal performance;
  • An increase of 1.2L/day in milk yield – 15 independent trials;
  • A 15% increase in live weight gain – 19 independent trials;
  • Available in 2L bottles and 5L cans for liquid application or in a 20kg bag for dry application. A 2L bottle or 20kg bag treats 100t of silage;
  • Full range of applicators available for liquid and dry application.

World’s most tested silage additive

Ecosyl is backed by more independent trial evidence than any other silage additive.

  • 26 independent trials have shown that Ecosyl increased silage digestibility by an average of three units;
  • More than 30 independent trials have shown that Ecosyl treatment leads to an increase of 5% in silage dry matter intake by animals;
  • 15 independent animal trials showed that Ecosyl-treated silage led to an increase in milk production of 1.2 litres/day.
  • Nineteen independent trials showed that Ecosyl-treated silage gave an increase of 15% in daily liveweight gain in growing animals;
  • 28 independent trials showed Ecosyl treatment gave an increase of 50% in dry matter recovery – amounting to an extra 35t of silage dry matter in a 1,000t clamp;
  • Trials have shown that Ecosyl treatment improves true protein in silage by 3.5%.

Millions of unique bacteria

Ecosyl contains the unique MTD/1 strain of the lactic acid bacteria Lactobacillus plantarum. It also contains the bacteria Pediococcus pentosaceus and potassium sorbate, a safe, non-corrosive food and feed-approved preservative.

This special blend is proven to give improved fermentation and better aerobic stability, leading to higher-quality silage that delivers better animal performance.

Ecosyl is guaranteed to deliver one million of these unique MTD/1 bacteria per gram of grass, leading to a rapid fall in the pH of the silage, thereby bringing about fast, efficient fermentation.

Ecosyl gives a 3:1 return

Research in Ireland and elsewhere has found that every euro spent on treating silage with Ecosyl inoculant gave a return of at least €3 in increased milk yield and animal performance.

Using Ecosyl, even in silages that are wilted, will enhance silage quality. An analysis of the results of some 50 animal performance trials carried out in Ireland shows the economic benefits to improving silage digestibility.

The best silages (75% DMD), when offered as the sole diet, sustain a milk yield of 23L/day and a daily liveweight gain of 1.1kg/day in finishing steers.

Poor-quality silage do not even support animal maintenance.

Increasing silage DMD from 68% to 73% increases milk yield by 1.65L/day and carcass gain by 0.12kg/day, or 18kg over a 150-day finishing period.

More information

For more information on Volac’s Cut to Clamp initiative, just click here and for additional information on the silage additive Ecosyl, click here