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Farmers should consider moving from a conventional three-cut system to one that involves cutting every five to six weeks, a leading silage expert has suggested.
Presenting data from a Welsh study at an Alltech webinar last Thursday, Dr Dave Davies from Silage Solutions highlighted the yield and quality differences between a three-cut and five-cut system.
Where lighter crops of grass are taken off at shorter intervals, regrowth is faster, and overall the five-cut system produced an additional 0.92t of dry matter per hectare (DM/ha) when compared with the three-cut alternative.
The silage made from five cuts was also higher in energy, averaging 0.48MJ/kg DM more.
Bigger yields of higher ME grass meant the five-cut system produced 18,582 more MJ/ha over the season.
Assuming that it takes 5.3MJ to produce 1kg of milk, the five-cut system had the potential to yield over 3,500l more milk per ha, worth around £1,000 at current prices.
Overall, it’s around £1,500 [per ha] in a beef or dairy system by this multi-cut approach
In beef cattle, the extra MJ would support an additional 465kg of weight gain.
However, young leafy grass will also have higher protein content, with the Welsh study suggesting that over 600kg more crude protein per ha was ensiled with five cuts.
At feed-out, less concentrate is then required to sustain animal performance, adding to the total financial benefit.
“Overall, it’s around £1,500 [per ha] in a beef or dairy system by this multi-cut approach,” said Davies.
Cutting height
When it comes to cutting height, Davies said that farmers often cut too low (below 7.5cm), increasing the risk of soil contamination, which will be detrimental to subsequent silage fermentation.
“If we cut at 7.5cm, the only thing we are leaving behind is undigestible fibre. There is no positive reason whatsoever to be cutting so low,” he said.
We can actually mow, harvest and pick up in the same day if our wilting procedure is correct
Where the cut grass is left on a bed of stubble, it will wilt faster. Grass should also be spread immediately after cutting as the stomata in a grass plant (which allow water to evaporate) only remain open for a couple of hours once cut. When stomata are open grass will lose 100l/t/hr, compared to only 20 l/t/hr when closed.
“We can actually mow, harvest and pick up in the same day if our wilting procedure is correct. Overnight, there is very little wilting. We should be cutting earlier in the day, when the dew has risen and try to pick up that same day when dry matter has hit 30-32%,” said Davies.
Getting to around 30% DM will negate any potential issues with high nitrates in the crop, or any contamination from slurry that has not been washed in.
However, the longer the wilt, the higher the in-field losses (as sugar is converted to carbon dioxide and water).
Davies also prefers a silage merger over a rake when rowing up grass, as it is less likely to pick up soil.
Additives
When it comes to silage additives, he described it as “the icing on the top”.
If choosing to use a biological additive, Davies emphasised that for NI conditions, Lactobacillus plantarum must dominate the product, and it should produce at least 1m bacteria per gram of forage.
Clamp
In the clamp he advises farmers to use side sheets, and to use an oxygen barrier silage film on top, covered with one sheet of conventional black plastic. Gravel bags should be used around the edges.
To prevent slippage in a clamp, he said the key was to ensure good consolidation throughout, so grass should be ensiled in even 15cm layers, and rolled consistently.
“We start compacting with the first load, and we do the same compacting as we go up” he said.
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