Thinking more about how silage clamps are sealed could deliver sizeable benefits in terms of forage quality and herd performance, as well as reducing plastic use.
TEXT PHILIP WINSTANLEY
At a time when all producers are focused on making maximum use of home-grown feeds to cut down on input costs and reduce carbon footprints, the way that silage clamps are sealed could have a bigger impact than many realise. So says Silostop Agri’s Tim Brewer.
“Switching from multiple sheets of traditional black plastic to a single sheet of high-oxygen-barrier film could cut silage waste from 15% to 5%,” he says. “That’s a reduction in silage waste of two thirds, or an extra 10% of forage available for the herd.”
Such reductions in silage waste and improvements in feed quality are being seen on UK units using high-oxygen-barrier (HOB) films, and these observations are supported by the results of comprehensive trials across Europe.
One study reveals a 42% reduction in waste in the top layers of silage clamps sealed with HOB film compared to standard polyethylene film. “The proportion of silage judged inedible by herds was also reduced with material stored under the HOB film compared with the standard sheeting system,” says Mr Brewer. “And the aerobic stability of the uppermost layer of silage under the HOB film was also higher.”
He says these results correlate with work carried out at France’s INRA Research Centre, where using HOB film saw a total silage loss of just 7% compared with more than 15% where traditional black polyethylene film was used.
“And, while mean silage density was similar for both, the total amount of silage dry matter removed for feeding was 17% higher for clamps were HOB film was used, reflecting lower losses during the storage period.”
Advantages of HOB film also extend to the environment. “Work in the Netherlands has shown the total weight of plastic used in a 40m x 12m clamp using standard film to be 241.5kg. This compares to just 43.4kg – just 18% of the standard film weight – when a HOB is used,” he says.
“In terms of primary energy needed to produce film, at 78.1MJ/kg, this was 18.9GJ for standard covering and just 3.39GJ for the HOB alternative. It required less than 20% of the energy to produce the HOB film for a silage clamp compared to that required for standard polyethylene.”
As for reducing greenhouse gas emissions, manufacturing of HOB film releases 92.3kg of CO2 but standard film produces 514.4kg.
Hampshire-based independent nutritionist Martin Attwell says that using HOB films to reduce silage clamp losses can have a significant impact on the bottom line.
“Grass is cheaper than concentrate feed, regardless of rationing system, so producing as much energy from silage as possible will always improve overall profitability,” he says. “Using HOB film, and paying close attention to detail when clamping silages, not only saves money, but also improves milk-from-forage calculations.” A typical silage clamp, measuring 20m across, 50m deep and filled to a height of 3m will hold around 600 tonnes of silage at 30% dry matter. Losing 10% less silage as waste in such a clamp produces an additional 60 tonnes of silage.
Silage analysing at 11.5 MJ/kgDM will yield 11,500 MJ/kgDM for every tonne of dry matter. If we use a realistic value of 90% of that energy making it from clamp to cow, that’s equivalent to 10,350MJ/kgDM. The energy needed to make milk is typically 5.3MJ/ kgDM per litre, so the extra 10,350MJ from silage would potentially produce 1,950 litres of milk. An additional 60 tonnes of silage will produce an additional 117,000 litres of milk.
At 40ppl, that’s more than £46,000 of additional milk revenue, or a 45-tonne reduction in concentrate use. At £350/t, that’s a saving of almost £16,000.
Cheshire-based producer Halton Farms is targeting a 40% increase in milk production from forage and minimising silage clamp waste is a key priority. “Average milk from forage is currently around 2,500 litres and we’re aiming to push this to 3,500 litres,” explains Tom Halton, who runs a 500-cow herd near Congleton with his wife Karen and son Jack.
The herd is averaging 11,000 litres, at 4.0% butterfat and 3.4% protein, on three-times-a-day milking, and the Haltons are taking steps to keep bought-in-feed costs to a minimum. “High volumes of top-quality forage are absolutely key to the business’ future sustainability,” says Tom.
He’s seen many benefits since moving from several layers of polyethylene sheets to a Silostop Max HOB film and secure cover. “Individual sheets are difficult to work with, particularly in windy conditions. It was such a tough job that after a hard day’s silaging it was all too easy to leave the sheets off so you’re building waste into the system from the very start.
“Even when the clamp is fully sealed, achieving an airtight join between the individual sheets is almost impossible, so that’s another area where waste creeps into the system.
“And as soon as the clamp was opened for feed out we faced the same resealing problem.”
He says that since switching to a HOB film they are closer to 5% in terms of silage waste. “We were heading towards 15% with our previous clamp-sealing approach. But the HOB film simplifies the silagemaking process, reduces stress at a busy time of year, and increases the amount of high-quality silage available to the herd.
“We’ve seen silage crude protein levels reach 20% since making the switch.
“There is also less feed left by the cows in the trough, dry matter intakes have definitely increased, and we feel the potential risk of mycotoxin problems is also much reduced.”