Recent dry weather could pose a problem for many units as they head towards first-cut silage, with potentially high dry matter silages leading to aerobic instability.
To counter this, Colin Shorrock of the Denis Brinicombe Group suggests silages may benefit from shortening chop length to aid ensiling. “Clamps should be filled quickly with plenty of thin layers and be rolled regularly to ensure sufficient consolidation of grass.” But Dr Shorrock reminds producers not to chop too short, as this can affect digestibility.
John Allen of Frank Wright agrees and says recent suggestions over increasing chop length should be treated with caution. “Increasing chop length can reduce the risk of sub-acute acidosis, but longer chop length is contrary to best silage making practice and the drive to maximise total dry matter intakes.
“Longer chop-length material is more difficult to consolidate, increasing the risk of poor fermentation. And this is particularly true of dry silages, which are likely to be a common feature of this year’s warm spring. Recent history shows silage dry matter is increasing, averaging 31.7% in 2005 compared with 35.5% in 2006.”
Dr Allen adds that feeding longer-chop material can be problematic,as it tends to stay in the rumen longer, slowing digestion and depressing appetite and hence total dry matter intake. “Farmers shouldn’t increase chop length when silage dry matter is predicted to be about 30%.
“Should the season turn wet and expected dry matter fall below 25%, then there may be a benefit in making some longer-chop silage, provided clamps are well consolidated and sealed.”
And while Dr Allen is keen not to give a definitive chop length, he suggests farmers should aim for material under 20mm long rather than the 25mm much grass is cut to at the moment.
Looking at the need for additives he believes grass analysis and cover levels suggest they could be a worthwhile investment this spring. “Sugar levels are particularly low in grass shut up for silage, with samples so far averaging 1.5% sugar and 18% dry matter. Protein levels are equally low at 20.6% and nitrates, which many people would expect to be high given the lack of growth this year, are running at 284mg/kg compared with the accepted danger point of 1000mg/kg.”
With sugar levels low, he says additives could be vital to ensure good silage fermentation early in preservation. And with light first-cut crops likely, he advises using an additive to improve digestibility.
To ensure effective consolidation and fermentation, Dr Shorrock recommends using direct-cut grass for the last few loads on clamps to add extra weight and aid compaction. “Alternatively, finish the clamp witha layer of brewers’ grains or anything wet and dense to exclude air.”