When it comes to making silage, and regardless of whether it’s in a clamp or in bale, one of the most important things to have at the forefront of your mind is oxygen. Or more specifically, how to reduce it in the silo at all times.
According to Dr Dave Davies, a director at Silage Solutions, increasing the density of silage at the time of harvesting is the first big step farmers can take towards oxygen reduction. Best of all, this is easily achieved in bales by using a high density baler with chopping.
"Chopping the forage during bale formation has two big advantages" explains Dave. "Firstly it reduces the amount of oxygen trapped in the bale and secondly it releases sugar into the bale and so encourages a more rapid lactic acid fermentation. Both of these factors increase the silage quality and reduce the risks of undesirable microorganisms such as yeasts, moulds and listeria."
He continues: "There are also impressive savings to be enjoyed. Chopped bales are at least 10% heavier than their unchopped counterparts helping to reduce the costs of production. The best way to illustrate this is by way of an example.
"Let's assume that the average cost of baling, wrapping, carting and stacking a bale is £8 per bale. Using chopped bales as opposed to unchopped ones would allow you to achieve the same quantity of forage with 10% fewer bales. That means a saving of £80 for every 100 unchopped bales produced. That's a major advantage and before we even fully examine the benefits in terms of improved silage quality."
Benefits are proven by scientific research
The advantages of employing chopped silage are more than just conjecture. They're proven by scientific fact. A study carried out by IGER Aberystwyth (now IBERS) - the leading biological, environmental and rural sciences research establishment - compared chopped and unchopped bales from the same grass fields. It found significant differences in some of the chemical constituents of the silage.
Pointing to this research, Dave says: "Firstly the IBERS's study revealed a pH of 4.30 in the chopped bales compared to 4.52 in the unchopped ones - the lower pH being a result of better fermentation. In addition, less sugar had been used to achieve this improved fermentation with 37 g/kg DM remaining in the chopped bales compared to 26 g/kg in those that were unchopped. This equates to 6.6 kg more sugar per 600kg bale." Dave continues: "As one would expect, the lactic acid concentration was also higher in the chopped bales whilst the improvement in fermentation had resulted in silage with a slightly higher dry matter. For the chopped bales this measured 329g/kg FM compared to 319g/Kg FM for the unchopped. Put another way, that's 6 kg more silage retained per 600kg of bale. Finally there was 25% less ethanol in the chopped bales. Ethanol is produced by undesirable microorganisms such as yeasts implying a lower yeast population with increased bale density. Combined, these results clearly show the benefits producing a denser bale can have in terms of silage quality."
Reduced Oxygen, reduced mould
As well as improving chemical composition, it seems the production of denser silage can also reduce mould. Dave points to a study in the US to illustrate the point: "It is well known that the higher the levels of oxygen in a bale, the greater the growth of yeasts moulds and listeria as all of these organisms require oxygen to grow. So it's of particular interest that a clamp silage trial conducted in North America found some significant results when it examined silage produced using good and poor compaction after 100 days of ensiling.
"In every gram of the poorly compacted silage, they discovered 100,000 yeasts per gram of silage whereas in the well compacted silage there were fewer than 100. Whilst not directly comparable to bales, this information coupled with the ethanol findings from the IBERS study does suggest that the same lower yeast levels are likely to be found in denser bales." Dave continues: "These yeasts instigate aerobic spoilage and will result in heating and moulding of the silage. Their reduced presence in dense bales means that should its wrap become damaged, it is far less likely to become mouldy than one made from looser material.
"Alongside this, oxygen can't penetrate to the same depth as it can with less dense silage. As a result, any mould that does occur won't be able to grow as deeply into the bale, helping to reduce losses and the risks to animal health risks caused by listeria and mycotoxins."
In addition, this reduced yeast growth can also offer benefits when feeding a bale out - and especially for a lower level of stock. Ironically it seems, and despite there being more silage in a chopped bale, it will probably remain cooler and unspoilt for longer than an unchopped counterpart. Taking all this into account, the argument for producing a denser bale appears to be a strong one. As Dave Davies concludes:
"There are no reasons why you shouldn't use a chopper baler to increase bale density if you have option and in fact there are plenty of reasons why you should. It's a simple step that can ultimately lead to the best of both worlds. Better silage and lower production costs."
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