Q&A: Experts answer farmers’ multi-cut silage questions

Getting high yields of quality milk at a low cost, while maximising animal welfare has always been key to the dairy industry. And is even more so now, with the unrelenting pressure on prices.

A recent survey of 457 farmers conducted by Kingshay dairy consultants showed nearly all respondents wanted to produce more milk from forage.

And a survey of 187 dairy farmers, conducted in December by Germinal and Volac, revealed 89% aimed to increase milk from forage, with 64% saying grass silage is more important now than it has been previously.

So, it’s clear dairy farmers are trying to increase yields from both fresh and preserved grass. There are several ways of doing that, but one of the increasingly popular methods is multi-cut silage.

A multi-cut silage system sees more frequent silage cuts taken at shorter intervals, rather than the more traditional three-cut system in the UK.

Many dairy farmers tried multi-cut for the first time last year and questions have cropped up. Farmers Weekly put some of these questions to a panel of forage and nutrition experts.

What do you see the key nutritional benefits of multi-cut silage to be?

RW Multi-cut systems produce a consistent quality product and high-yielding dairy cows need consistency. Multi-cut systems produce higher energy density and crude protein crops.

If you look at intakes on herds moving to multi-cut systems, DM intakes increase by 1-3kg DM a cow a day. This allows you to target 35-40% or more of your milk produced from forage.

See also: Benefits of switching to a multi-cut system

Do I need to take the first cut earlier in the season? When should that be and how often should I be cutting?

RW Go with the plant, cut the plant early and regularly at 28 to 30 days.

Remember rye grass is at its highest quality with three leaves; a fourth leaf means one is dead and rotting, so energy density will be lower.

Plus, you also increase the risk of bringing potentially harmful yeast and molds into the clamp.

Be organised so you are ready to go when the plant is, make sure you tell the contractor chop length and mowing height, and don’t assume he will know.

JB The date for first cut will vary depending on a number of factors, such as where you are in the country – but it should certainly be before grass comes into head.

For people wanting to make multi-cut, consider cutting at intervals of less than six weeks – because six weeks gives grass the opportunity to head.

A one week delay in cutting after heading could mean 3.6 units of digestibility value lost and getting extra D value can save you feed. 

Does it require more or less fertiliser and if more, how easy is it to stay within nitrogen limits?

BW Calculating the timings of spring nitrogen is important.

We still talk about two units of N/acre being used a day, so if you apply 80 units, you need 40 days between application and cut. The modern equivalent is 2.5kg/ha.

You should not be using any more than 60-70 units per application, so if you’re looking to cut between the turn of April/May then you need to be applying N in the second to third week of March.

There does seem to be more soil residual N around these days.

You must always consult your Facts qualified advisor and RB209 before applying any fertilisers.

What’s the best chop length?

JB With the leafier crop from multi-cut, there is a higher risk of slippage on the clamp therefore we recommend considering a chop length of at least 5cm, depending on dry matter.

This gives structure to the clamp and can help increase fibre in the silage. Cutting very short crops of multi-cut grass won’t give you the forage you desire.

DD Chop length should be varied according to DM and quality.

If it is all young leafy material and 32% DM then 3-5cm. If its 28-30 then 5cm minimum, but if its wetter and below 28, then it needs to increase in length even up to 10 cm at 22% DM.

What puts me off is the contamination risk. How do I make sure there is no fertiliser or slurry contamination in subsequent cuts?

BW We need to be applying the slurry to the soil, we don’t want to be applying it to the leaf because of what happens in the pit.

Slurry needs to be tested and applied at approximately 25,000 litres/ha. We need at least 10 weeks between slurry and first cut, so it needs to be as early in winter as possible. It should ideally be applied with a trailing shoe or injector, and never a splash plate.

Ideally, we would only apply bagged fertiliser between cuts as the risk of contaminating the grass leaf with slurry is too large. However, I appreciate this isn’t always possible. If applying slurry between cuts please cut back the application and make sure the slurry is of a very low dry matter about 2%. Again, ideally inject the slurry or use a trailing shoe applicator. 

How quickly does the crop need to be wilted and clamped?

JB You need to be cutting, spreading, wilting and clamping it within a day. If it’s a good day, you’ll easily get 28-32% dry matter. Grass should be cut in the morning with a mower conditioner and ted out within two hours to allow quick wilting.

This is the time frame the stomata are open, so tedding needs to be quick to maximise the moisture loss from stomata.

Grass should be rowed up just before the forager.

DD The ideal DM would be somewhere about 32%. The quicker you can reach this the better, so monitor in the field. 

The Dutch are advocating a much higher DM (into the 40% DM range), but with UK clamps and weather, this is a mistake as it significantly increases field losses and feed-out losses. 

Ideally 24 hours, with an absolute maximum of 36 hours, wilting period. More than 36 hours you can lose more than 4% units of digestibility (0.7 MJ/kg DM ME) in the field. 

However, with the lower yield/cut from the multi-cut, the wilting time will be quicker so a double whammy benefit for energy content (higher energy at mowing and lower energy losses due to the shorter wilt time).

I have experienced slippage in the clamp with multiple cuts in it. What’s the answer? Should I step the clamp?

JB Clamp management is really important. The clamp needs to be consolidated in small layers – a maximum of 15cm. The layers should be flat, not sloping. Seal the clamp quickly after harvest and use side sheets. A minimum of two covers are needed and I would almost argue to use three. Definitely look to keep plenty of weight on top of the clamp.

RW Clamp density is everything. Make sure you don’t have product coming in too fast and the guy with the buckrake knows how to make a clamp with thin layers of grass starting from the outside and evenly spread over the top of the surface so it can be effectively consolidated. Once you think it is rolled enough roll it for another hour

The silage face should be nice and flat like the below picture.

DD Slippage tends to occur with lower DM crops generally below 25% DM. However, the multi-cut system provides additional challenges because the low fibre content makes it more prone to slippage.

Therefore, the key things are that the chop length should be longer – even at 30% DM, 5cm would be ideal, this will also help in improving rumen use of the silage. 

In addition, the clamp should never be filled at an angle greater than 20deg to the horizontal. More than one cut in the same clamp, which means re-opening and filling a subsequent cut also adds a risk, as if the subsequent cut has a lower DM it will have a heavier weight and could lead to slippage through additional weight on top.

Care is required and I would prefer if possible to fill most of the subsequent cut in front of the previous cut, providing you can keep to the rule of 20deg maximum filling angle. 

Stepping at feed-out is a possibility to reduce slippage, but it can increase other problems such as rain water contamination and spoilage.

What sort of silage additives do I need to use in the clamp?

DD Grass harvested in a multi-cut system will be higher protein and lower sugar than a standard cut because of the changes during grass growth. This means the silage fermentation will be potentially more challenging and so an inoculant that contains just homofermentative species of bacteria such as Lactobacillus plantarum or Pediococcus should be used.

Additives with heterofermentative species such as Lactobacillus buchneri, L kefiri and L brevis are less efficient silage fermenters and require more sugar to stabilise the pH. Even in combination with homofermentative bacteria, they will prove less efficient.

In addition, it will be young and leafy material so the levels of aerobic spoilage yeasts will be lower and the crop will consolidate more easily, making control of aerobic spoilage at feed-out easier.

Also, higher protein crops are inherently more aerobically stable. The correct silage additives are very beneficial but they must be used in combination with best ensiling and feed-out practice.

My main concern is contractor charges. Is there any way to reduce this?

BW Contractor costs will be higher in a multi-cut system, but I’d argue that the energy level increase you get will pay for the contractors and a lot more (see ‘Contractor costs weighed up’, below). It may be that your contractor will consider a reduced rate for subsequent cuts given that he is getting more work overall.

Should I be concerned about soil compaction if we’re doubling traffic over the ground?

BW This is a good question, as compaction is a major issue in grassland management, irrespective of the grazing or silage making system. If compaction is suspected, normally indicated by poor grass yields, then soil assessment should be carried out in late summer in the form of soil structure digs.

Dig holes in the suspected compacted part of the field and also under a hedge or an electric fence in the middle of a field. This will give you a good idea of whether you have soil compaction in areas. If compaction is found then appropriate measures need to be taken in the autumn preferably to alleviate the problem. 

DD This is an interesting question. I would always advocate where possible floatation tyres for field work (not on the clamp of course). However, there will be fewer traverses across the field each time compared with a standard cut when forage harvesting due to the lower yield.

So maybe the impact is not as great on soil as you may expect. However, I would recommend looking at the AHDB website on controlled traffic to try and reduce the impact as much as possible.