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AgridianDairy KB

As-fed vs dry matter basis

Definition

Section titled “Definition”

Feed amounts, nutrient values and prices are given on one of two bases:

  • As-fed (also “as-is” or “wet basis”): the weight of the feed including its water, as it sits on the truck, in the pile or in the bunk.
  • Dry matter (DM) basis: the weight with all water removed. Rations are formulated on a DM basis, and nutrient analyses (crude protein, NDF, energy) are usually reported on a DM basis.

DM% is the share of the feed’s as-fed weight that is dry matter: DM% = 100 − moisture %. Dry hay and grain are about 85–90% DM; silages roughly 30–40%; wet byproducts can be 20–35%.

Sources of a DM% value, in order of preference for a given load or period:

  1. Actual: measured on a sample (lab, oven, microwave, Koster tester).
  2. Expected: a running average or recent test for that commodity.
  3. Fixed / contract: a DM% written into the purchase contract.
  4. Comparative / standard: a reference DM% used to standardize payment (see below), not a measured value.

A ton in US feed trade is a short ton of 2,000 lb, not a metric tonne (2,204.6 lb).

Paying for forage on a DM basis

Section titled “Paying for forage on a DM basis”

Wet forages (silage, haylage, green chop, wet byproducts) vary widely in moisture, so buying by as-fed ton pays for water. Contracts often standardize to a reference DM%: the as-fed tons are converted to the tons that would have been delivered at the standard DM, and that adjusted tonnage is paid at the contract price.

Example: 100 as-fed tons of corn silage at 32% DM, contract standard 35% DM: adjusted tons = 100 × 32 / 35 = 91.4 tons paid.

Formula

Section titled “Formula”

Plain text:

DM%              = 100 − moisture %
DM lb            = as-fed lb × DM% / 100
As-fed lb        = DM lb / (DM% / 100)
$/DM ton         = $/as-fed ton / (DM% / 100)
$/as-fed ton     = $/DM ton × DM% / 100
Adjusted tons    = as-fed tons × actual DM% / standard DM%
Nutrient, as-fed = nutrient (% of DM) × DM% / 100

LaTeX:

W_{\text{DM}} = W_{\text{AF}} \cdot d
\qquad
P_{\text{DM}} = \frac{P_{\text{AF}}}{d}
\qquad
T_{\text{adj}} = T_{\text{AF}} \cdot \frac{d_{\text{actual}}}{d_{\text{std}}}

where W = weight, P = price per ton, T = tons, and d = DM fraction (DM% / 100).

How to pull it in DC305

Section titled “How to pull it in DC305”

DM values and feed weights are not in DC305. DM% comes from lab reports, on-farm moisture tests or contract terms; as-fed weights come from scale tickets and the mixer scale.

DC305’s only role is the cow count used to turn pen DM totals into per-cow DMI (COUNT BY PEN).

Typical range

Section titled “Typical range”

Herd context: US feeds commonly used in Holstein freestall or dry-lot rations.

Feed Typical DM%
Corn grain, dry 86–89%
Soybean meal 88–90%
Alfalfa hay 85–90%
Corn silage 30–40%
Alfalfa haylage 35–50%
Wet distillers grains 30–35%
Wet brewers grains 20–28%
Lactating TMR 45–55%
  • Standard DM for corn silage contracts is commonly set around 30–35%.

Common mistakes

Section titled “Common mistakes”
  • Comparing prices across bases. A $60/as-fed ton silage at 33% DM is about $182/DM ton; comparing that to a $250/ton hay quote (as-fed, ~88% DM, about $284/DM ton) on the as-fed numbers gets the value backwards.
  • Inverting the adjustment. Adjusted tons = as-fed × actual / standard. A wetter-than-standard load should pay fewer tons, not more.
  • DM% vs moisture %. Labs report one or the other; 35 is not the same number on both.
  • Fraction vs percent. Multiplying by 35 instead of 0.35 is a 100× error. Some systems store DM as a fraction, others as a percent.
  • Metric tonnes mixed with short tons. About a 10% difference.
  • Stale DM%. Using a harvest-time test for months of feed-out, or one test for a whole bunker.
  • Nutrient values on mixed bases. Ration software expects DM basis; some feed tags and quotes give as-fed.
Section titled “Related”