A simple switch from multiple sheets of traditional black plastic to a single sheet of high oxygen barrier (HOB) silage film could cut silage waste from 15% to 5%, says Tim Brewer of silage film specialists Silostop Agri.
At a time when all producers are encouraged to use home-grown feeds, he believes the approach could deliver significant productivity and environmental benefits.
“We’re seeing significant reductions in silage waste and improvements in feed quality across the UK with HOB films and this is supported by comprehensive trials across Europe.
“One such study of over 50 individual pieces of work has shown a reduction in waste of 42% in the top layers of clamps sealed with HOB film compared to standard polyethylene film.
“The proportion of silage judged to 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.
“In addition, 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.”
The 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.”
According to Hampshire-based independent dairy nutritionist Martin Attwell, reducing silage losses from 15% to 5% at the clamp can significantly impact a dairy operation's finances.
“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.
“Using high oxygen barrier film and applying attention to detail when clamping not only saves money, it also improves milk from forage calculations.”
He explains that 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.
“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.”
He adds that even with a moderate-sized dairy herd, the financial impact of 10% extra forage is significant.
“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.”
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 as one of their key priorities.
“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.”