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Understanding forage analysis
The nutritional quality of forage is assessed by analysing dry matter (DM), metabolisable energy (ME), crude protein (CP) and other metrics.
After you get a copy of the analysis report, take time to understand the values and how this may affect diet formulations, DM intakes and animal performance.
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Desirable levels for grass silage
Your silage production targets will differ according to your farm aims and the stock group you are feeding. Discuss your results with your nutritionist or feed adviser.
Quality of silage:
- Good: 70
- Moderate: 65
- Low: 60
Definition: The portion of feed left after water is removed. Reported as a percentage.
Importance to livestock performance: Allows you to compare feeds accurately and work out how much an animal can eat.
Quality of silage:
- Good: 11.5
- Moderate: 10.5
- Low: 9.5
Definition: Energy available to the animal after losses in faeces, urine and gases. Usually reported as MJ/kg DM.
Importance to livestock performance: Supports maintenance, growth, reproduction and lactation.
Quality of silage:
- Good: >70
- Moderate: 65
- Low: <58
Definition: Digestibility of organic matter, expressed as a % of DM.
Importance to livestock performance: Higher D-value means better feed quality and animal performance.
Quality of silage:
- Good:16
- Moderate: 12
- Low: 10
Definition: Estimate of total protein based on nitrogen content (N × 6.25). Reported as % DM.
Importance to livestock performance: Essential for growth, reproduction, milk production and general health.
Quality of silage:
- Good: >3 or <4.5
- Moderate: <4.5
- Low: >8
Definition: Measure of acidity and an indicator of fermentation quality in silage.
Importance to livestock performance: Achieving target pH during fermentation preserves the nutrient value of silage until re-exposure to air at feed-out.
Quality of silage:
- Good: 8
- Moderate: 7
- Low: >10
Definition: Total mineral and trace elements in the feed. Reported as % DM.
Importance to livestock performance: Indicates mineral levels and possible soil contamination. Producers of grass silage should be targeting less than 8%. Silage with 10% ash has reduced ME and may indicate soil contamination or poor fermentation.
Quality of silage:
- Good: 42–50
- Moderate: 50–55
- Low: >55
Definition: Total fibre, including hemicellulose, cellulose and lignin. Reported as % DM.
Importance to livestock performance: Affects bulkiness and intake; high NDF may limit voluntary feed intake.
Definition: Feed’s resistance to pH changes during fermentation (ensiling).
Importance to livestock performance: High buffering capacity may hinder effective silage fermentation.
Use the nutritional analysis to guide which groups you are going to allocate forage to:
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Good: Feed to finishing stock, ewes carrying multiples, milking cows, growing dairy replacements
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Moderate: Feed to growing cattle, autumn-calving suckler cows, ewes carrying singles, late lactation cows
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Low: Feed to dry stock, spring-calving suckler cows