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Published 1 February 10
The feeds available to dairy herds fall into four main categories:
- Moist feeds
- Mineral and other supplements
They are generally assessed for their value in ruminant feeding on the basis of a number of specific laboratory analysed parameters.
The most widely used of these are:
- Dry Matter - DM (g/kg or %) The proportion of the feed that is not water - the higher the dry matter the less dilute the nutrient source.
- Ash (g/kg DM or %) The amount of material in the DM that is not organic matter and so only of value to the animal for its mineral content.
- Digestibility - D-Value (%) The extent to which the organic material contained in the dry matter is digestible.
- Metabolisable Energy - ME (MJ/kg DM) The energy actually available to the cow after accounting for losses in digestion, gases and urine.
- Fermentable Metabolisable Energy - FME (MJ/kg DM) The amount of ME potentially available to the rumen microbes.
- Neutral Detergent Fibre - NDF (g/kg DM or %) The total fibre content, also indicating the bulkiness of the feed.
- Crude Protein - CP (g/kg DM or %) The total nitrogen content, including non-protein nitrogen as well as true protein.
- Rumen Degradable Protein - RDP (g/kg DM or %) The amount of nitrogen available to the rumen microbes.
- Digestible Undegradable Protein - DUP (g/kg DM or %) The amount of nitrogen available for digestion which escapes rumen degradation.
Some laboratories report measures as g/kg while others use percentages in their analyses. To convert g/kg into % divide by 10. To convert % into g/kg multiply by 10.
A range of other measures - including Acid Detergent Fibre (ADF), 18.5 27.6 4.06 3.19 sugar & starch contents, lactic & butyric acid contents, ammonia nitrogen, Quickly Degraded Protein (QDP) and Slowly Degraded Protein (SDP) are variously also used to characterise feeds.