If you had a handy list that gave you practical clues on how to make better grass silage – and therefore potentially save on bought-in feed costs – would you use it?
Or, would you ignore it and make silage the way you’ve always made it?
Well, this type of list does exist. It’s called your silage analysis. All you have to do is understand what it’s telling you.
A silage analysis doesn’t just provide the basis for ration formulation. It’s also packed with pointers for improving how silage is made.
Typically, the main areas people focus on with the analysis are those concerned with nutrition. For example, metabolise energy (ME), digestibility (D value), protein, and % dry matter (DM).
Clearly, these are important. But there’s lots of other valuable information on there. For example, information that sheds light on how efficient the silage fermentation has been, how well the protein has been preserved, and whether the silage was contaminated with soil and/or slurry.
This is all crucial information to know if you want to make better silage.
Silage might ‘look’ nutritious. But if the quality of the fermentation has not been up to scratch, it’s very likely that losses in DM and/or nutrients will have occurred.
If the fermentation was particularly poor and the silage has become unpalatable so that cows aren’t eating it, a huge amount of the time and money you invested in making will also have gone to waste.
Knowing the underlying causes of these problems is the first step to correcting them. As a starting point, examine your silage analysis for each of the following:
Lactic acid (LA) and volatile fatty acids (VFA)
These figures give you an insight into the quality and efficiency of the fermentation.
In an efficient fermentation, beneficial bacteria convert sugar in the grass into lactic acid, and nothing else. This is ideal because lactic acid is very good at preserving silage (essentially ‘pickling’ it against the growth of unwanted bacteria). However, it’s also ideal because the process of converting sugar only to lactic acid retains more than 99% of the energy contained in the fermented sugar and all its DM.
By contrast, in a poor fermentation, undesirable bacteria (for example those that get into silage from slurry or soil) produce a range of far less desirable acids – called volatile fatty acids (VFAs) – as well as other wasteful by-products, such as carbon dioxide. Carbon dioxide is wasted DM and a greenhouse gas. VFAs are weaker at preserving silage than lactic acid, and are associated with higher DM and energy losses.
Certain undesirable bacteria, for example, can waste 17% of the energy in the fermented sugar and 41% of its DM.
Ideally, you want a high ratio of lactic acid to VFAs. An absolute minimum should be 3:1. But it ought to be higher – such as 5:1 or higher still.
To help achieve this, a proven additive such as Ecosyl can be a huge help. Ecosyl applies 1 million beneficial lactic acid-producing bacteria per gram of forage treated. But more than this, the bacterial strain it contains – Lactobacillus plantarum MTD/1 – is highly efficient at driving the fermentation to being dominated by lactic acid, rather than the unwanted VFAs and by-products.
If you have high VFAs, look at using Ecosyl and look at minimising contamination with soil bacteria (see below) and slurry bacteria. For example, if you must apply slurry between cuts, apply it as soon as possible after cutting onto clean stubble and ahead of regrowth. This will maximise sunlight reaching the undesirable bacteria to help kill them off, and will help the fresh grass to grow above the slurry.
A point to note is that where silage heating is a problem and an additive such as Ecocool, containing Lactobacillus buchneri, that produces some acetic acid has been used to counter this, this would cause VFAs to increase to some degree.
Ash content
The ash content figure on a silage analysis helps you assess the level of soil contamination in the silage.
Again, it should be as low as possible. An ash figure above 8% indicates a problem with soil contamination. Minimise this by rolling fields and checking soil isn’t being introduced into silage by machinery, for example by rakes and tedders being set too low so they dig in and flick up soil into the mown grass.
Energy value – ME and digestibility
Metabolisable energy (ME), which is the amount of energy available to the cow, is a nutritional measure and is linked to digestibility (D value), since the more digestible the silage, the more energy the cow can derive from it.
Aim for 11 ME as a minimum, and 70 D value or above for milking cows. As well as taking steps to achieve a better fermentation in order to preserve more energy (for example, treating with Ecosyl in trial work has preserved an ME of 11.3 MJ/kgDM in grass silage, compared with 10.6 MJ/kgDM in untreated silage) regular reseeding also helps, as does mowing grass at the correct timing.
This is because younger leys tend to be naturally higher in energy. Also, if you leave cutting until after heading, then grass digestibility starts to fall by about 0.5% per day.
Crude protein (CP)
Protein is often reported as crude protein on a silage analysis. This figure is calculated form the total amount of nitrogen in the grass, and therefore includes both 'true' protein, as well as other non-protein nitrogen compounds.
A good figure is 16-18% protein. Higher values of 20% or more may be recorded in young, leafy grasses, but may also be indicative of residual fertiliser.
Low protein might be a sign that the grass was cut too late, since younger grass tends to be higher in protein, or possibly that fertiliser dose was too low. But it can also mean grass was wilted for too long. This is because, until it is stable in the clamp, enzymes in the grass will break protein down.
Ammonia (NH3)
Ammonia is often reported as a percentage of the CP. Higher values are undesirable, and figures greater than 10% are indicative of protein breakdown and a poor fermentation.
Wilting rapidly, ensiling promptly and achieving an efficient fermentation will all help to preserve protein. Also, make sure you optimise nitrogen inputs so the grass has chance to fully utilise what is applied.
Dry matter (DM) percentage
Targeting a DM of 28-32% should minimise losses at every stage of the silage making process, from field to feed out.
To make it easier to reach this %DM quickly, cut at the correct growth stage, because lighter, leafier grass is easier to wilt, and assess whether increased tedding is required.
If silage is too wet or too dry, cows struggle to eat enough of it – which is not something you want with high-yielding cows.
pH
The more moisture the silage contains, the more acidic (lower pH) it will tend to be, which increases the acid load on the cow.
The ideal pH will depend on the %DM, since drier silages need less acidity to make them stable. For silage at 30% DM, aim for pH 4.0. Wilting to the optimum 28-32% DM helps to avoid excess acid loading.
Intake potential
Intake potential is a combination of several factors – including %DM, pH, fermentation quality, chop length (with shorter chop lengths increasing intake potential) and D value (since more digestible silages travel through the cow faster).
Aim to optimise each of these parameters because a higher intake potential is important for maximising milk from silage. Intake potential should be 100 minimum, but 110-120 is more beneficial.
Understanding your silage analysis is just the first step—acting on the insights it provides is what truly makes the difference. By regularly reviewing your results and making adjustments, you can refine your silage-making process year after year, leading to better feed quality, improved milk yields, and reduced reliance on costly bought-in feeds.Whether it’s fine-tuning your wilting times, optimising fermentation with a proven additive like Ecosyl, or minimising contamination risks, small changes can lead to big improvements. Use your silage analysis as a roadmap to continuous progress—because better silage means a more profitable farm.
For more expert insights and practical tips on making consistently better silage, explore our website.