Reduce feed costs with a new approach to your silage preservation


The continuing high prices of bought-in concentrates, fertilisers and other inputs, together with marginal farm gate prices for both milk and meat, suggests that farm businesses need to look closer to home to see if anything can be done better to reduce the financial gap.

There probably is, but because it is something we have been doing year in and year out, it is all too easy to become complacent about how we can get the most out of the feedstuffs we grow on farm. For example, we often take silage for granted, and maybe don’t give too much thought to how we can get more from it, and thereby reduce expenditure on bought-in concentrates. This silage season it could really pay to think hard about making the best silage possible. This means looking at your silage making process from the crop in the field right through to feedout.

I will not go into great detail here about how to grow a good silage crop, as the preparations required are well understood; slurry applications no later than 8 weeks before cutting; fertiliser applications, 1st cut - 80 - 140 kg N / ha, subsequent cuts - 60 - 90 kg N / ha, consider NVZ rules; rolling to give a clean sward at the start of the growing season free of stones, molehills and other contaminants. Grass will utilise nitrogen at the rate of 2 units per day in ideal growing conditions, and since these don’t occur too often it is well worth testing the crop a couple of days before cutting, to ensure that there is no excess in the crop.

Cut at the optimum date to ensure high DOMD, protein and sugar and low nitrate levels. Use a mower conditioner and aim to leave stubble of between 2½” - 4” to avoid soil contamination and allow rapid re-growth. The objective should be to get the crop to at least 25% DM as quickly as possible with the minimum of tedding (to reduce soil contamination risk and save diesel). Wilting for longer than 24 hours will result in increasing nutrient losses in the field.

Once the crop is ready to pick up, the objective should be to get it into the silo as quickly as possible, filling using the ‘Dorset Wedge’ method, in thin layers, and with good compaction to exclude as much air as possible as quickly as possible. I know that every farmer knows this, but it is surprising how often we see badly filled, poorly consolidated clamps of silage. Get this bit wrong, and its ‘downhill from here’! Giving the clamp a good roll when it is full is a total waste of time, money and diesel! It is far better to roll well throughout filling (ideally using a 4-tonne Silapactor that can increase compaction by up to 40% compared with conventional methods - reducing dry matter losses and getting more in the clamp) and get the clamp sealed quickly.

Use new plastic side sheets, now available in convenient 4x50 metre rolls, new O2 Barrier 2in1for maximum oxygen exclusion, or ClampFilm vacuum sheet as the primary top sheet, followed by a new top sheet. Cover with heavy-duty ClampNet, gravel bags or ClampTiles. Silage is far too valuable to compromise by using second hand sheeting, which is almost certain to allow air into the clamp somewhere.

As can be seen from the chart in fig 1, the percentage of the total DM that can be lost throughout the silage process can easily amount to 30% or more of the total DM. It is worth remembering that these losses are most likely to be from the most valuable DM components in terms of nutrient value, so attention to detail in order to minimise these losses will always pay.

Having filled and sealed their clamp as efficiently as possible, many farmers will keep their fingers crossed in the hope that what comes out of the clamp is ‘OK’. Is there anything else that could have been done to ensure that the silage is of the highest feed value possible when it reaches the stock? In order to answer this question we need to have some understanding of the microbiology of the crop, and how this influences the fermentation process.

On every gram of fresh forage there is a cocktail of microscopic bugs; aerobic bacteria, lactic acid bacteria, enterobacteria, yeasts, moulds, clostridia, bacilli, and acetic acid bacteria. Without a lot of work in a laboratory it is not possible to know the makeup or concentration of this cocktail, but fig 2 gives an idea of the range of populations of the organisms that are most important during the ensiling process. Lactic acid bacteria can easily be outnumbered by the undesirable coliforms and clostridia. To understand why this is important we need to see what these different organisms do in the anaerobic conditions we have created in the clamp.

Good (homofermentative) lactic acid bacteria convert one molecule of either glucose or fructose (the most common sugars in grasses) into two molecules of lactic acid:-

1 glucose or fructose ? 2 lactic acid

Lactic acid is an important energy source for rumen bugs.

Less desirable (heterofermentative) lactic acid bacteria have a more wasteful fermentation characteristic:-

Glucose ? lactic acid + ethanol + CO? + Water
3 Fructose ? lactic acid + acetic acid + 2 mannitol + CO? + Water
Glucose + 2 Fructose ? lactic acid + acetic acid + 2 mannitol + CO? + water

Acetic acid, ethanol and mannitol are not used by rumen bugs and CO? obviously has no feed value, but it does represent a loss of valuable dry matter and, more importantly, energy. An acetic acid level in the fermented silage of 55g/kg DM will have resulted in a loss of 10 tonnes of CO? from 250 tonnes of DM ensiled!!

The coliforms (enterococci) cause even more loss and as we have seen their population can be as high as, or higher than the good lactic acid bacteria:-

1 glucose ? 1 acetic + 1 formic + 1 CO? + H?O


1 glucose ? 1 ethanol + 2:3 butanediol + 1 CO? + H?O

Finally we have the two types of clostridia, those that degrade sugars and those that break down protein:-

Saccarolytic Clostridia

1glucose or 2 lactic acid ?1 butyric acid + 2 CO? + 2 H?O

Proteolytic Clostridia

Amino acids or amides ? NH? + CO? + H?O

From all of the above it is quite clear that there is a high risk of valuable nutrient loss if we rely on the complete cocktail of natural ‘wild’ bugs to provide our fermentation. There are three courses of action which can be taken to reduce this possibility. The first is to ‘flood’ the crop with a culture of desirable (homofermentative) lactic acid bacteria, in order to outnumber and out-compete the undesirables. This can result in a rapid drop in pH and a better retention of sugars and protein. However, it is likely to produce silage that is not aerobically stable, because the fermentation creates an environment ideal for the spoilage yeasts and moulds that are also present on the silage. These organisms will become active as soon as the clamp is opened and air reaches them.

The second is to inoculate with heterofermentative bacteria. The most common species used, lactobacillus buchneri, produces the type of fermentation detailed above. Although this is wasteful of dry matter, the argument by those that advocate its use is that it can give improved aerobic stability because some of its fermentation products control spoilage yeasts and moulds. Unfortunately, it cannot be relied upon to work completely reliably, and overall losses can be greater than when using no treatment at all. (Danner et al 2003).

Probably the most reliable way to minimise all the losses associated with fermentation and aerobic spoilage is to reduce the numbers of harmful organisms to a minimum. This can now be achieved using Safesil, a special blend of food grade preservatives which eradicates and controls all the major spoilage organisms. In 2009 Dr.David Davies at IGER, Aberystwyth showed, in comparative tests with a market leading inoculant, that Safesil minimised ethanol levels, demonstrating its ability to control the organisms that produce this alcohol, across a range of dry matters, and reduced yeast and mould numbers to barely detectable levels resulting in extraordinary aerobic stability (260 hours compared to 64 hours with inoculant treatment).

Because of Safesil’s action against undesirable fermentation bacteria the lactic acid bacteria present on the crop had little competition and as a result less sugar was used to produce an excellent lactic fermentation. This gave the additional benefit of reducing DM loss during fermentation to a very low level (1.39%) when compared to treatment with a biological inoculant (7.72%).

In trials and on farm Safesil has the proven ability to promote superb aerobic stability across a wide range of dry matters and on all silage crops from grass to wholecrop and maize. Since aerobic instability, which is indicated by heating silage, is the single biggest cause of nutrient loss in silage on all farms, Safesil should be considered as the preservative of choice, giving a high level of return on investment.

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