Research shows benefits of High Oxygen Barrier films

Research shows benefits of High Oxygen Barrier films

Research into the benefits of single sheet high oxygen barrier (HOB) films compared to multiple sheets of traditional black plastic have shown significant productivity and environmental benefits, says Tim Brewer of silage film specialists Silostop.

Trials from around Europe and further afield have shown significant reductions in silage waste, improvements in feed quality and an overall reduction in energy use and associated carbon footprints, he explains.

“One of the most compelling of these is a meta-analysis of over 50 individual pieces of work which showed a reduction in waste of 42% in the top layers of clamps sealed with a high oxygen barrier film compared to standard polyethylene film.

“The proportion of silage judged inedible by livestock was also reduced with material stored under the HOB film compared with the standard film covering system and the aerobic stability of the uppermost layer of silage under the HOB film was much greater too.

“These results correlate with work carried out at the INRA Research Centre in France where HOB film gave a total silage loss of just 7% compared to over 15% with traditional black polyethylene film.

“The trial was carried out using a Silostop covering system as the HOB film with protective net and gravel bags to secure it compared to a standard polyethylene film weighed down by tyres.

“A single crop of primary growth perennial ryegrass was harvested on 12th and 13th June after a 48-hour period of field wilting and was ensiled in adjacent silos simultaneously without any additive. Period of storage for both was 240 days.”

Despite the same approach for both silos, very different results were seen when they were opened, he explains.

“Whilst mean silage density was similar for both, the total amount of silage DM removed for feeding was 17% higher with the HOB material, reflecting lower losses during the storage period.

“Butyric acid concentration was much higher in the polyethylene covered clamp compared to the Silostop HOB one – 17.2g/kg DM as opposed to 7.35g/kg DM – indicating poorer fermentation quality in the traditionally covered clamp with a correspondingly lower pH for this clamp too.

“The study clearly demonstrated the extent to which total losses can be reduced and silage quality improved using an oxygen barrier film compared to the standard silage covering technique.

Advantages of HOB film extend to environmental ones too, he says.

“Covering ensiled forage maize with a single layer thin HOB film has been shown to give large reductions in primary energy and greenhouse gas production compared to the normal practice of covering clamps with two layers of standard film which is much thicker.

“Work in the Netherlands has shown the total weight of plastic used in a 40m long by 12m wide clamp using standard film to be 241.5kg whereas with an HOB film it was only 43.4kg – just 18% of the standard film weight.

“In terms of primary energy needed to produce the film at 78.1 MJ kg film this was 18.9 GJ for the standard film and 3.39 GJ for the HOB one. So it’s taking less than 20% of the energy to produce the HOB film for a silo compared to that for the standard polyethylene approach.

“When it comes to greenhouse gas reduction, whilst the manufacturing of the HOB film released 92.3 kg CO2 to the atmosphere, with the standard film it was 514.4kg – over 5.5 times more.

“At a time when everybody needs to produce their home-grown forages as efficiently as possible whilst limiting any harmful effects on the environment, HOB films have an awful lot going for them.

“The number of people still using a range of variously-sized black plastic sheets plus a few worn-out tyres with rusty wires thrown on top is still worryingly high, especially when there is such a downside to not sealing a clamp properly.

“We wouldn’t tolerate 15% storage loss for any other agricultural product yet as the research shows that is often the case with clamped forages.”

“Our experiences in the UK suggests a drop in silage wastage from 15% to 5% as a result of better clamp sealing when people switch from traditional black plastic to HOB films is a common outcome.”


Tim Brewer recommends looking at five key management points when switching over to HOB films.

  1. Plan ahead

Single sheet films are available in range of sizes and the best fit will depend on individual circumstances, he explains.

“For a start, you’ll also need to be sure you can handle the weight and size of rolls selected and work out whether going from side to side across the clamp is the best option or if going from front to back is better.

“The overall aim is to keep the number of joins to a minimum to avoid potential air ingress, so it’s best to work with somebody who understands the different films and sizes available and who can help you make the right decisions.

  1. Make sure you’re using a genuine high oxygen barrier

Not all plastic films are created equal and it’s important to choose a genuine high oxygen barrier if you want to get the best results, he adds.

“A proper high oxygen barrier will have an oxygen transmission rate of less than 5 cm3/m2 of film, which means almost no air can get into the clamp in use, but with typical black silage plastic this is more like 300 cm3/m2 .

“When this is stretched out to make an imitation oxygen barrier cling film, it can reach 1000 cm3/m2 so quite a lot of air is able to pass through the film resulting in considerable spoilage and dry matter shrinkage in the top layers.

"These thin transparent polyethylene films can appear to give a reasonable result with a visual reduction in top layer spoilage, but their extremely high oxygen transmission rates results in high DM losses.

“We’ve also ensured all our films are recyclable, but that’s not the case with all films.

“Again, you need to talk to somebody who understands this and be prepared to ask the questions about oxygen transmission rates and recycling.”

  1. Use sidewall sheeting wherever possible

Once you’ve made your overall plan, sealing the sides of the clamp using an appropriate wall film is the first operation you should carry out, he says.

“Make sure the clamp is as clean as possible then line the walls with side sheeting to make sure oxygen cannot enter through the walls.

“Ideally, leave 0.5m of film at the base of the walls so it overlaps onto the floor of the clamp. This will help secure the film when the silage starts to be put in.

“An extra 1m of film should also be left at the top of the wall so this can be folded back over the silage once the clamp is full. Make the silage surface as dense and smooth as possible by lots of rolling.”

  1. Manage films correctly

Type of forage will also play a key role in choosing the optimum film, Tim Brewer points out.

“If you’re using a multi-cut system, where you will be repeatedly opening the clamp up to add material, a stronger film is advisable. This can then be used with a secure cover.

“If you’re clamping maize or wholecrop silage where the clamp is filled and then left until it is opened, the lighter sheets with an Anti-UV cover are the best option.

“Silostop Anti-UV covers, for example, provide full UV and physical protection and are designed to work in conjunction with just one layer of thin but strong Silostop Orange HOB film.”

  1. Secure films properly

Whichever approach you take, bags and purpose-made mats are the best materials for keeping covers in place and minimising pest damage, he advises.

“The other advantage is that sheeting time can be cut in half and that’s important in making sure clamps are sealed every evening when you are filling them and also whenever you remove material from it over the winter.

“The easier this is to do, the more likely it is to happen and this alone can help minimise silage loss considerably.”


Reducing silage losses from 15% to 5% at the clamp can have a significant impact on the finances of a dairy operation, says Hampshire-based independent dairy nutritionist Martin Attwell.

“Grass energy is cheaper than concentrate feed energy regardless of the system so no matter how you farm, getting as much energy from your silage will always improve overall profitability.

“With high fertiliser prices and the dry spring in some parts of the country, it is even more important to prevent clamp wastage this year.”

“Using high oxygen barrier film and applying attention to detail when clamping not only saves money, it also improves milk from forage calculations.”

A typical silage clamp measuring 20m across and 50m deep filled to a height of 3m will contain around 600t dry matter (DM) of silage at 30% DM, he explains.

“So if you are able to cut clamp wastage from 15% to 5%, you are going to end up with an extra 60t DM of silage.

“Silage of 11.5 MJ ME/kg will yield 11,500 MJ ME for every tonne of dry matter. If we use a realistic value of 90% of that energy making it from clamp to cow, then that’s 10,350 MJ ME.

“The energy taken to make milk depends on its quality, but it’s generally 5.3 MJ ME per litre so the extra 10,350 MJ from silage would potentially produce 1950 litres of milk. So that extra 60t DM will produce an extra 117,000 litres of milk.

“At 40p/litre of milk that’s over £46,000 of extra milk revenue or, if you want to look at it another way, each 1.0t DM lost would need 0.75t of concentrate to replace it, so if you can save 60t DM of clamp loss you’ll be saving on 45t of extra concentrate.

“At £350/t that’s a saving of almost £16,000.”

Even with a moderate sized dairy herd, the financial impact of 10% extra forage is significant, he adds.

“If you’ve got a 250-cow herd producing 8,500 litres/year with a 6-month indoor feeding period you’re going to need to make around 700 tonnes DM of silage every year and if you are reducing clamp losses from 15% to 5% the effect on the bottom line is huge.”


Somerset dairy producer Mark Humphry is increasingly focusing on improving silage clamp management to enhance the quantity and quality of forage, which is is a key business goal.  

Run as a business partnership with wife Belinda and son Matt, Bartletts and Southey Farm, Isle Brewers, a Duchy of Cornwall tenancy, now has 360 crossbred commercial milkers.

“Producing lots of high quality grazing and silage is absolutely fundamental for us, so improving the efficiency of clamp sheeting has been a real priority in recent years.

“We changed to the Silostop Orange sheet and Anti-UV cover system recently and this has proved a great move. We were originally very sceptical that a thin sheet would do the job and hold up to everyday use.

“But we’ve definitely seen reduced spoilage on the top and this not only reduces the worry that this could find its way into the cows, it also eliminates the time spent removing waste from the clamp which can be considerable.

“It’s much simpler to use too. The Silsotop orange all-in-one film that we use now means when you have finished with your silage clamp in the evening, it’s a really easy job in terms of covering the clamp back up so you’re more tempted to do it than waiting until the next day.’

Covering a silage clamp used to be about the worst job you could do on the farm, Mark admits.

“I used to reckon it took us longer to cover a silage clamp properly than it did for us to put the silage in there, but that has all changed now.

“It takes less time to cover the clamp properly at silage making, management is much simpler during the winter feeding period and we get better, more consistent forage to feed to the cows as well.”


With rising input prices across the board, Cheshire milk producers Halton Farms Ltd are targeting a 40% increase in milk production from forage with minimising silage clamp wastage one of their key priorities.

The farm’s new clamp sealing system is based on a Silostop Max high oxygen barrier film for the main sheet and an Secure cover with the results being very impressive, says Jack Halton.

“In one move we’ve managed to simplify the silage making process, reduce stress at a busy time of year and increase the amount of high quality silage available for the cows.

“We’re definitely getting near that 5% figure now in terms of the much reduced waste we’re seeing and were easily heading towards 15% with the old approach.

“It’s not just the reduction in spoiled silage visible at the clamp, but there’s less material left in the troughs by the cows so the overall palatability and digestibility of our silage has obviously improved.

“Dry Matter intakes have definitely increased and the potential risk of mycotoxin problems resulting from poorly conserved grass is also much reduced.”

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