Feed energy – Dutch system
Definition
The Feed Unit Milk (VEM), the Dutch feed energy system, is an energy parameter for dairy farmers. It represents the net energy content of a product for lactating cows. For beef cattle, the Feed Unit Beef Cattle Intensive (VEVI) is used.
The Feed Unit Milk is related to the energy content of 1 kg of standardized barley (barley with a specific hectoliter weight and starch content). By definition, the energy content of this kilogram of barley is set at 1,000 Feed Unit Milk (VEM). Because Feed Unit Milk is a relative value, it has no unit.
Energy Levels
The choice to define a nutrient without a unit makes comparisons easy in practice.
For example:
- A product containing 1,100 Feed Unit Milk has 1.1 times more energy than 1 kg of barley (or 10% more).
- In ration calculations, the energy density can be expressed as 1,000 Feed Unit Milk per kg dry matter.
In other feed evaluation systems, energy may be expressed in megajoules per kilogram (MJ/kg). The Net Energy Lactation (NEL) of 1 kg of barley is 6.9 MJ NEL — meaning 1,000 Feed Unit Milk = 6.9 MJ NEL.
Digestibility
The Feed Unit Milk is calculated based on the amount of digestible nutrients, including:
- Crude protein
- Organic matter
- Crude fibre
- Crude fat
- Carbohydrates (sugar, starch, and other carbohydrates)
Digestibility, expressed as the Digestibility Coefficient of Organic Matter, plays a major role in determining the energy value.
In roughages such as grass, the time of harvest strongly influences the energy content.
Older grass contains more lignin, resulting in lower digestibility and thus lower Feed Unit Milk values.
Energy Requirements
To produce 1 kg of FPCM (Fat-Protein Correct Milk), milk with 4% fat and 3.3% protein, a cow needs about 460 units of Feed Unit Milk.
A cow producing 30 kg of milk needs about 19,000 Feed Unit Milk. Of this, about 5,300 units are needed for maintenance, the remainder for milk production.
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