How to read a silage analysis report
Your lab report lands on the desk and it's full of abbreviations and percentages. Here's exactly what each figure means, what a good result looks like in the UK, and how to use the analysis to get more from your silage.
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Why silage analysis matters
Silage is usually the biggest single cost input on a livestock farm — and for many systems it makes up 50–70% of the winter diet by dry matter. A difference of 1 MJ ME/kg DM between a good and average silage is worth roughly 1 kg of concentrate per cow per day. On a 200-cow dairy farm over a 150-day winter, that's the equivalent of 30 tonnes of concentrate — around £6,000–£9,000.
Yet many farmers use silage analysis results reactively — only when performance disappoints — rather than as a tool to build the ration from the outset. Getting the analysis done immediately after clamping (or at least before feeding begins) and using the numbers to formulate the ration is one of the highest-return management actions on any feeding system.
What each figure means
Dry Matter (DM %)
The percentage of the sample that is solid material — everything except water.
1st cut typical
28–35%
2nd cut typical
22–30%
Good result
30–34%
Watch out
Below 20% or above 40%
Very wet silage (low DM) loses effluent and nutrients. Very dry silage can heat and cause secondary fermentation. First cut is usually drier than second cut.
Metabolisable Energy (ME, MJ/kg DM)
The energy available to the animal after digestive losses. The single most important number on the report.
1st cut typical
10.0–11.2
2nd cut typical
10.5–11.5
Good result
11.0+
Watch out
Below 9.5
ME is calculated from D-value. Every 0.5 MJ/kg DM increase in ME is roughly equivalent to 1 kg of concentrate per cow per day in a dairy ration.
D-value (%)
Digestibility of organic matter — the percentage of the organic fraction the animal can digest.
1st cut typical
65–72
2nd cut typical
68–75
Good result
70+
Watch out
Below 63
D-value is closely related to ME: D-value ÷ 10 × 1.5 ≈ ME. D-value falls rapidly as the grass matures past the early heading stage — cutting date is the single biggest influence.
Crude Protein (CP %)
Total nitrogen content × 6.25. Includes both true protein and non-protein nitrogen (NPN).
1st cut typical
12–16%
2nd cut typical
14–18%
Good result
14–16%
Watch out
Below 10% or above 20%
Very high CP (>18%) in second cuts from heavily fertilised swards often contains a lot of NPN (ammonia), which has less feeding value than true protein. Check the ammonia N figure alongside CP.
pH
The acidity of the silage. Lower pH means better fermentation and preservation.
1st cut typical
3.7–4.2
2nd cut typical
3.7–4.2
Good result
Below 4.0
Watch out
Above 4.5
Dry silage naturally achieves adequate preservation at a higher pH. Wet silage (below 25% DM) needs pH below 4.0 to be stable. A high pH on wet silage indicates poor fermentation.
Ammonia N (% of total N)
The proportion of total nitrogen present as ammonia — an indicator of how much protein has broken down during fermentation.
1st cut typical
Aim <7%
2nd cut typical
Aim <7%
Good result
Below 7%
Watch out
Above 15%
High ammonia N means protein has been degraded to a less useful form. It increases the pH required for stability, contributes to poor palatability, and is often caused by delayed wilting, soil contamination, or slow clamp filling.
NDF (Neutral Detergent Fibre, % DM)
Total cell wall content — the structural fibre. High NDF reduces intake because the rumen fills faster.
1st cut typical
45–55%
2nd cut typical
40–50%
Good result
Below 50%
Watch out
Above 60%
NDF is the best indicator of potential intake. A silage with high ME but also high NDF can disappoint in practice because the animal cannot eat enough of it. Second cuts from leafy swards tend to have lower NDF.
ADF (Acid Detergent Fibre, % DM)
The less digestible fraction of the cell wall, mainly cellulose and lignin.
1st cut typical
28–36%
2nd cut typical
25–32%
Good result
Below 32%
Watch out
Above 38%
ADF is used to calculate D-value and ME. High ADF means the grass was cut late or the sward contained a high proportion of stems and dead material. Unlike NDF, ADF cannot be improved by processing.
WSC (Water Soluble Carbohydrates, % DM)
The sugars available as a fermentation substrate when ensiling.
1st cut typical
5–15%
2nd cut typical
8–18%
Good result
10%+
Watch out
Below 5%
High WSC grass (ryegrass-dominant swards, cut in sunny conditions) ferments more readily and tends to achieve lower pH. Low WSC is common in wet years and on heavily shaded swards — these benefit most from an additive.
What to do if your result is below target
Low ME / D-value
Increase the concentrate allocation to compensate for the energy shortfall. Use the ME value to recalculate the ration — don't assume last year's diet still works. The silage meal reduction calculator can help you quantify the trade-off.
High ammonia N / poor pH
Don't blend poor silage with good silage expecting it to average out — palatability and intake will both be suppressed. Feed poorer silage to lower-demand stock (dry cows, stores) if possible, and review your ensiling process for next year.
Low DM / wet silage
Wet silage has a lower energy density per kg fed (because more of the weight is water). Increase feeding rates to compensate, or check whether the silage face is heating — secondary fermentation in wet silage can rapidly destroy ME value and reduce intakes.
Let Clover analyse your report
Upload your silage analysis to AgriOps and Ask Clover to build a ration around it. Clover knows your silage values, your stock numbers, and your other feed stocks — and gives you specific answers, not generic averages.
Clover Feed AssistantRelated tools
Silage Required Calculator
Work out how much silage you need for winter
Silage Meal Reduction Calculator
Calculate concentrate savings from better silage
DM Required Calculator
Calculate daily dry matter requirements by stock type
Ration & TMR Mix Calculator
Build and cost a TMR ration from your silage and feeds