BGS Silage Day

Published 26 April 13

Making the Cut

At the recent BGS/Silage Advisory Center (SilAC) Silage Day an expert team talked about how to get the best from this year's silage making and storage.

At Lower Medhurst Farm, Congleton, Stuart Yarwood explained that his father has passed on best practice in silage making to him and he in turn hopes to pass this onto the next generation.

In his father's day they were feeding 6,000 litre British Holstein cows and the farm made about four cuts of silage between May and September, using an acid additive.

Nowadays the farm has Holstein cows yielding 9,000 litres, therefore the silage has had to change with them. The need to get the intakes into them is all important.

  • Lower Medhurst Farm now uses a contractor do all 160 acres
  • They can mow the whole area in one day and with the weather forecasts available now it's much easier to identify the right weather window.

They found that silage with 11.5ME and a relatively low DM of about 28% was just going through the cows, so they needed a second forage and now grow whole crop.

As the herd expanded, they took on extra land and buildings, they have been using big bale silage to help meet the increased forage requirements.

The first cut silage goes into the clamp and then most of the second and third cut goes into haylage, which goes into the main ration at about 3kg/cow/day.

With the wet grass and short weather windows last summer, the big bales proved to be a real lifeline this winter and spring. The big bales had about 20% DM and they work out about £10 per bale. Lower Medhurst Farm has provided the young stock and dry cows with their forage this spring.

Stuart thinks that with the increasingly unpredictable weather it's important to build flexibility into the system. "With some of the warm springs followed by the cold and wet conditions we've had over the past few years there aren't any hard and fast rules about when grass grows. You need to take the opportunities when they arise."

Managing factors to reduce clamp silage losses, Dave Davis, SilAC

Many of these factors apply to both clamp and big bale silage.

It's old data but still true. ADAS data shows 25-40% DM losses in clamp silage, 0.2-8% in bailed silage and 15-30% in maize.

There are good reasons to control losses. Three areas that you need to pay real attention to detail to are:

  • Management of the crop
  • Management of harvesting
  • Management of the clamp or bale.

"It's all about getting the right bacteria working quickly and well in order to preserve the plant's energy."

Cutting height is crucial - 10cm will mean better fermentation and reduce the amount of undesirable bacteria from soil contamination this equates to less wastage. For permanent pasture the cutting height can be lower.


  • Even in a wet year you need to spread the silage to help with wilting
  • The quicker you spread the quicker the increase in wilting
  • Target DM should be around 32% on most UK farms. If however you're not there after 24 to 36 hours wilting ensile it anyway.

However tempting don't fill trailers completely - you'll only lose some on the way back to the clamp.



  • Getting the oxygen out at the start of the fermentation process is crucial
  • Oxygen trapped in the clamp will mean higher yeast growth and will also be there ready to grow when you open the clamp
  • Some of the best silage seen is when the farmer is actually rolling or on 'duty' by the clamp
  • Rolling needs to keep up the loads of grass being delivered. Tell the contractor to hold on if you need extra time to roll
  • If you can't push your finger into the face of the silage it's well compacted
  • You want the tyres touching across the top
  • Don't overfill the clamp - put excess into big bales. If too full to seal properly air will get in and that means more wastage. Think about maybe making a separate 'pile' of excess for the first few feeds.
  • Sealing is important; a thick film sheet clings down quickly reducing the oxygen entering the clamp. It pays for itself in reduce wastage of silage crop
  • Use a side sheet
  • Use sand bags instead of types against the wall to get a tight seal
  • The main aim during filling, storage and feeding out is to exclude as much oxygen as possible. Spoilage means variation in silage quality and cows don't like that.

What to do if you need to leave the clamp overnight during silage making

Pull the sheet over and put on a few tyres to hold it down

Don't roll before you start to fill the next morning as it will reduce the silage quality. Fill the first load in the morning to about 20cm (not the normal 15cm).

An increasing number of contractors have the facility to weigh crops so you can get a print out of what each field gives. You can tell which fields are underperforming but this will also give you an idea of the losses you're incurring during silage making. There will come a time when you pay a contractor for silage quality.


Management factors to improve baled silage quality,Rhun Fychan, SilAC

Benefits of bale silage

  • Flexible management system
  • Variable harvest dates
  • Economic harvesting of small areas
  • Flexibility of feeding
  • Excellent system of rapid sealing, increase rates of fermentation and reduces spoilage
  • When feeding out only open wheat need, reduce wastage.

Methods to adopt to reduce losses in big bale silage.


Ensure that you have got a good bale shape. If you haven't dense corrugations will form on the surface which means the film will come apart. The layers of the film need to be together to work well and the corrugations provide pathways for oxygen to enter.

You want a smooth shoulder shape as all bumps and humps provide pathways for the oxygen to enter. A wide bale net (edge to edge) will help create smooth shoulders.

Chopping will increase bale density by 15% as it means more grass in each bale and therefore less air. Chopping also helps release sugars
leading to a quicker fermentation.

Film layers

A study, at Aberystwyth, showed the benefits of wrapping big bales in 8 layers compared to 6 or 4. With a higher number of layers you get less mould cover, less DM losses and a more efficient fermentation.

Financially, the costs of extra wrap and labour more than makes up for itself in reduced losses.

  • Count the number of times it takes to cover the bale, add one and then add 2 for 4 layers and 3 for 6 layers
  • The baler might control itself but you need to check its set up right for your specifications
  • The rollers need to be clean or the wrap will not be stretched
  • Check what film your contractor is using - but a wrap the manufacturer is happy to put their name to.


  • Bales wrapped by the stack have a much better film seal and less mould
  • Problems with birds with field wrapping
  • Cart bales back immediately, don't leave them in fields
  • Stubble damage creates holes, allowing oxygen in and wastage to occur
  • 6 layers of wrap reduce stubble damage to big bales
  • When dealing with wet big bales use 6 to 8 layers as they are more likely to become misshapen.


Silage Additives, Shirley Heron, Volac

Benefits of silage additives:

  • Improve fermentation
  • Reduce DM looses
  • Improve animal performance.

But additives won't make up for poor management. Double check you know what effect your additive has on animal performance as fermentation improvements don't necessarily affect animal performance.

Make sure your additive has been proved in feeding trials and that all trials are included not just those that worked!

  • Bacteria are living organisms and need to be alive and happy when applied in order to work. Treat your additive with respect
  • Read and follow the instructions
  • Wash system frequently with clean water.