Grassland farmers have been advised that it’s particularly important to analyse their grass before taking first cut silage this year.
The unusually long, cold, dry spell through spring could have several effects, which means grass composition is more unpredictable than in a typical year.
A particular concern is the combination of low sugar and high nitrate nitrogen, which don’t go well together. Low sugars limit the amount of lactic acid which can be produced, which is important for a stable fermentation, while high nitrate acts as a buffer, making the job of creating desirable acidic conditions more challenging still.
Although the cold, dry weather is expected to have slowed nitrogen uptake by the plant, this means much of it may remain available for use. If there’s a warmer, wetter spell before silage making, there could be a rapid uptake of this unused nitrogen, raising nitrate in the plant just before the silage is made.
“This unpredictability makes it more important than ever to analyse grass before cutting and will help determine the choice of additive,” says Michael Carpenter from feed and forage preservation specialists, Kelvin Cave Ltd. “There’s a wide range to choose from, each with its own distinct mode of operation, and we would recommend tailoring the choice of additive to the grass quality and cutting conditions.”
Don’t delay cutting
In the face of slow April grass growth, at around half the rates recorded in the same month last year, he also urges growers to resist the temptation of waiting for a heavier crop.
He says: “It’s far better to cut at the optimum stage than delay, as later cutting will reduce forage quality in terms of metabolisable energy and D-value [digestibility]. A later cut will also slow down regrowth, which will compromise cuts later in the year.”
He also advises growers not to ‘lower the mower’, again resisting any temptation to bolster grass yields, but instead, recommends targeting a residual of 7.5cm.
“Just like a later cut, a lower cut would also slow regrowth, while increasing the risk of soil contamination and raising the proportion of stem to leaf in the silage,” he says. “More stem means ME and D-value will again be lower, which reduces dry matter intake, increases undesirable methane production and has a significant impact on animal performance, whether that’s milk production or liveweight gain.” (See notes below.)
However, he warns that a lighter, leafy cut comes with its own risks, one of which is clamp slippage.
“It’s best not to give this type of grass too short a chop length and we recommend it is rolled in thin layers from front to back, rather than in the more traditional Dorset wedge,” he says. “Maintaining consistently high density throughout the whole clamp is also important and minimises the risk of a slip zone.” (See notes below.)
Dry matter is a further consideration and a higher DM will go some way to reducing any problem caused by high nitrate levels. But using an extended wilt to achieve this may be counterproductive as it leads to DM and energy losses, while wilting for over 24 hours is associated with significant increases in yeast, a spoilage organism of silage.
“As with nutritional quality, dry matter should be tested before cutting – and again that’s very important in this unusual season,” says Mr Carpenter. “This can be done using a simple, microwave DM test, as detailed by AHDB.” (See notes below.)
He also points out that a younger, more leafy silage, has the potential to lose moisture during wilting considerably faster than a stemmier crop.
If a light cut is taken, residual nitrogen should also be considered, and any fertiliser not taken up will be available for the following cut.
“We advise growers to calculate the amount of nitrogen they’ve taken off with the crop, as this will alter future slurry and fertiliser applications,” he says.
This can be done using a simple calculation, (as detailed in notes below), potentially saving pollution and wastage.
“The nub of the matter is that this year, different decisions may need to be made before making first cut silage as weather and growth conditions have been so unusual,” he says. “There is the potential for some good quality silage if it’s taken early and preserved with care. However, we urge growers to consult a company specialising in forage preservation which, like Kelvin Cave Ltd, should be willing to offer its customers a free grass analysis service to help put them on the right track.”
Safesil challenge in the ultimate preservative for challenging high Nitrate N or low sugar conditions to maximise quality from your first cut silage in these cold, dry spring conditions.
Please see Farmers Weekly article relating to the above.
Notes in relation to the above
Each 1% increase in D-value equates to an extra 0.26 litres of milk per day or increased daily liveweight gains of 40g/head/day in cattle and 20g/head/day in lambs (NIAB).
Each 1% drop in D-value results in an increase of 0.5 litres/cow/day in methane production due to indigestible fibre slowing rumen throughput.
More mature silages with higher neutral detergent fibre (NDF) have been shown to significantly reduce dry matter intake (Moorby et al).