Pay close attention to detail to mowing, wilting and fermentation if hoping autumn grass silage cuts will help to top up drought-hit silage stocks from summer, livestock farmers are being urged.
According to Volac technical business manager, Ken Stroud, resumption of grass growth in autumn will be a godsend for farmers facing forage shortages this winter. But it will be important to make the most of this, he says, by minimising losses in dry matter (DM) and quality in the field and in the clamp.
Although fresh autumn grass can be high in protein and digestibility, it can be challenging to wilt and preserve,” says Mr Stroud. “If poorly managed, DM losses might reach 20-25%.
“Difficulties wilting due to heavy dews and shorter days in autumn can result in wetter grass being ensiled, requiring a bigger fermentation. If this isn’t achieved, it means undesirable microbes present on the grass will be able to feed on the silage for longer in the clamp, consuming more of its DM and nutrients.
“On top of that, sugars available for fermentation are likely to be in shorter supply in autumn grass because there’s less sunlight for photosynthesis. And the number of beneficial fermentation bacteria naturally present on the grass is likely to be lower because of cooler temperatures.
If making autumn silage when ground conditions are soft there’s also more chance of unwanted bacteria getting into the silage from soil. Some unwanted bacteria also produce compounds that make silage less palatable, so livestock might refuse some of it – the last thing you want if forage stocks are tight.
All of these factors underline the need for extra attention to detail when making autumn silage, Mr Stroud says.
If wilting times can be reduced while still achieving a suitable %DM, this can help the amount of sugar available for fermentation, he says, by reducing losses from the cut grass in the field prior to ensiling. Also effective clamp consolidation and sealing will aid conservation, he notes. But there is still an added argument for using a proven inoculant to dominate the silage fermentation with high numbers of good bacteria to boost preservation, he points out.
“For example, Ecosyl inoculant delivers a million MTD/1 bacteria per gram of forage treated,” he explains, “and results in rapid production of beneficial lactic acid, which quickly inhibits undesirable bacteria.
In research, Ecosyl has halved DM losses versus untreated grass silage, with treated silage also more digestible. Indeed, where grass was lower in digestibility to begin with, which is likely if autumn grass is stemmy, the benefit of Ecosyl over untreated silage on digestibility was even greater. Across a range of forages in independent research, cows fed silage conserved with Ecosyl also yielded on average 1.2 litres more milk/cow/day.
To speed up wilting of autumn grass, Mr Stroud advises tedding immediately after mowing, with an ideal target of reaching 28-32% DM content in the shortest possible time. But do not leave it too long to achieve this, he says. It might be better to harvest it sooner and ensile it at a lower %DM to reduce in-field sugar and protein losses, he adds.
“Also, if short on silage, don’t be tempted to mow grass too low for extra yield. The stem base is lower in digestibility and can introduce additional undesirable microbes into the clamp. Leaving a longer stubble to keep cut grass off the ground also aids wilting by letting air circulate beneath it, and allows the tedder to be set slightly higher, reducing the risk of it hitting the ground and flicking soil into the silage,” he adds.
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