Understanding Dry Matter in Animal Feed

Newsletter 104, published in November 2011 discussed a very important question asked  by a writer wanting to understand better how to understand dry matter in reference to ostrich rations.

The question asked:

“Blue mountain recommendation tells 2.1kg/day/bird for maintenance and breeder.  Is this the amount on air dry basis or dry matter basis?   I am confusing dry matter basis or air dry basis and I should be grateful to have your comment on this.”

This discussion proved it was confusion in language translation as the writer’s first language is not English even though he speaks and writes excellent English.  It does however illustrate the importance of understanding the correctly the moisture content of feed and how it relates to “TOTAL NUTRIENT INTAKE”.

In this discussion the writer was confusing “method of drying” as opposed to the resulting “dry matter” when calculating “total nutrient content” consumed.  Just to clarify further, the following explanations describe the differences in these terminologies.

Air Drying:
This is when ingredients are dried by air....it maybe forage lying in the field to be dried as hay by the sun.  It may be grains dried in the barn, free from artificial heat, but turned regularly until the correct dry matter is achieved to enable safe storage.  This is usually less than 14% moisture, with 10% to 12% moisture the optimum target.

Heat Drying:
This is the other method of drying forage crops or grains.  The crops are dried through an artificial heating system suitable for the crop being dried.

Both the above methods are appropriate with the method used dependent on the local conditions.  However, when formulating the rations to balance those ingredients it is important for the nutritionist to know the method used for drying and the resultant moisture content as drying methods can influence the micro-nutrients in the crop such as vitamins and enzymes.  Excessive exposure to the sun, for example can leach out nutrients.  Excessive artificial heat can destroy some vitamins and enzymes.    When hay is sampled for nutrient content, the vitamins and enzymes are rarely sampled as it becomes too expensive....the test usually covers only basics such as protein, fibre and maybe important minerals such as calcium and phosphorous.

Dry Matter Basis vs As Fed Basis
It is extremely important when calculating the “total nutrient intake” of any animal to know the moisture content of the feed fed to the birds...whether it is fed as dry food, grazed food, fed as silage or a combination of all.

Dry Matter and As Feed Moisture Content of Various Feed Ingredients
comparative dry matter

Dry Matter Basis is calculating “nutrient intake” on the total dry matter of the feed fed.

As Fed Basis calculates the total weight of the feed as fed, so includes any moisture.   When you weigh the feed to ensure your livestock receive the correct weights, this will include any moisture...that is “as fed basis”.    This paper explains this in greater depth.

The importance of understanding the “total nutrient intake fed” cannot be over emphasised.

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