Dry matter
Definition
The dry matter (DM) content represents the portion of a feed sample that remains after all moisture has been removed. It is the first laboratory determination performed on feed samples and forms the basis for all other analytical results and feed valuations.
Because nutrients are expressed per kilogram of dry matter, results can be compared objectively, regardless of moisture content.
Determination methods
Vacuum Drying Method
- A fixed amount of the sample is weighed and then dried overnight (> 4 hours) in a vacuum drying oven at 70–80°C.
- The remaining weight after drying represents the dry matter.
- This lower temperature prevents sugars from burning, making it suitable for samples with higher sugar content.
Standard Drying Method (103°C)
- Used when the sugar content is low (<4–5%).
- A fixed amount of sample is dried at 103°C until constant weight is achieved (> 4 hours).
- This method is commonly applied for routine analyses of compound feeds and raw materials.
Importance of dry Matter
The dry matter content serves as the foundation for:
- Feed comparison and evaluation (independent of moisture level).
- Nutrient calculations such as protein, energy, and fibre values.
- Storage and preservation decisions, as too little or too much moisture affects stability.
Dry matter in raw materials
- For compound feed raw materials, DM typically ranges between 85% and 99%.
- Compound feed generally contains around 88% DM.
- A lower DM content increases the risk of mould and reduces shelf life.
- When DM is too low, drying or acid treatment is recommended before storage.
Dry Matter in Silage
The dry matter content determines silage quality and influences preservation, fermentation, and feed value.
- Grass silage: optimal DM between 35–45%.
- Maize silage: optimal DM between 34–38%.
Factors such as chopping length, compaction, and sugar content also affect quality.
DM is routinely measured as part of the Forage Analysis.
Typical Dry Matter Levels in Silage
Source: CVB, 2011
|
Product |
Dry matter (%) |
| Grass silage | 30–50 |
| Maize silage | 30–40 |
| Straw | 83–86 |
| CCM silage | 50–65 |
| Fresh grass | 15–17 |
| Potato fibre | 14–16 |
| Brewer grains | 22–26 |
Practical considerations
- Dry matter too low:
- Higher risk of press juice loss and loss of preservatives.
- Use of a feed additive is recommended.
- Dry matter too high:
- Greater risk of heating (scalding) in the silo, especially at low feed rates.
- Additive use is also recommended.
An optimal DM content (~36%) in maize silage results in maximum usable feed value and improved starch content and starch resistance.
However, palatability may decrease slightly in drier silage, depending on the total ration.
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