As Sampled vs. Dry Matter Results

Analytical results are typically reported on both an as sampled and dry matter basis. Either can be used for ration balancing, and it is important to understand the difference between them and how each can be used most effectively. Consistency is important: when developing a ration or comparing different feeds, the results need to be compared on the same basis. Failure to do so will result in misinterpretation, improper formulation, and/or unjust comparisons.

A. Definitions
Moisture % = the percent water in the sample.
Dry Matter % = 100% – Moisture%. The dry matter (DM) represents everything in the sample other than water including protein, fiber, fat, minerals, etc.
As Sampled Basis – nutrient results for a sample in its natural state including the water. Also known as as fed or as received. Feed tag guarantees are typically reported on an as sampled basis.
Dry Matter Basis – nutrient results for a sample with the water (moisture) removed. Water has a diluting effect on the results. Results reported with the water removed allows for the direct comparison of nutrients across different feeds and often simplifies the ration balancing process.
B. Conversionsas sampled results can be simply converted to dry matter basis results and vice versa using the following formulas.
1. As sampled basis to dry matter basis:
Dry matter basis = As sampled basis/(DM%/100)
Example: Pasture
                    Crude Protein %                  
DM%
 As sampled
DM Basis
25
 4.0
?
      Crude Protein %, DM basis = 4.0 / (25/100) = 16.0%
2. Dry matter basis to as sampled basis:
As sampled basis = Dry matter basis x (DM%/100)
Example: Hay
                    Crude Protein %                  
DM%
 As sampled
DM Basis
90
?
12.0
      Crude Protein %, As sampled = 12.0 x (90/100) = 10.8%

On an as sampled basis, the hay appears better in protein. Removing the diluting effect of the water, the dry matter basis results reveal that the nutrient rich dry matter in pasture is superior to the hay.

C. Uses
1. As Sampled Results – feed guarantee results are typically reported on an as sampled basis on the feed tag or back of the bag. If a diet is composed primarily of dry feeds (i.e. hay, grain, oats), the as sampled results can be used for ration balancing. These feeds will all average about 90% dry matter (range 88 – 92%). Since the dry matter is consistent across all of the feeds in the ration, the as sampled results may be used.
2. Dry Matter Results
a. Ration development – Dry matter results should be used when the dry matter levels vary greatly between feeds in a diet. For example, hay and grain are normally 90% dry matter (10% water) while pasture is 20% dry matter (80% water). Eliminating the impact of water on the results simplifies the ration development process.
b. Intake – animals consume feeds to meet a daily need for dry matter. Recall that feeds can be split into two basic parts: 1) water and 2) dry matter or everything that is not water. It is the dry matter that contains all of the nutrients (protein, carbohydrates, fat, etc.), thus animals eat to satisfy their dry matter needs. This also means that animals need to consume more of wetter feeds to meet their daily dry matter needs. For example, an 1100 pound horse will consume about 20 pounds of dry matter per day. The amount of feed actually consumed can be determined by dividing the pounds of dry matter consumed by the percent dry matter of the feed. If this horse consumed only hay at 90% dry matter, it would need to eat 20/(90/100) or 22.2 pounds of hay. If the only feed was pasture at 25% dry matter, it would need to eat 20/(25/100) or 80 pounds of pasture. Comparing the two:
1. 22.2 lbs. of hay @ 90% dry matter = 2.2 lbs. of water + 20 lbs. of dry matter.
2. 80 lbs. of pasture @ 25% dry matter = 60 lbs. of water + 20 lbs. of dry matter. So to consume the same pounds of nutrient rich dry matter (20 lbs.), horses need to eat larger amounts of pasture.
c. Predicting feed intake – total dry matter intake is based on body weight, stage of growth, reproductive status and level of activity. Dry matter intake is expressed as a percentage of body weight. The table below lists a couple of examples.
Table. 1. Predicted dry matter intake (DMI) as a percentage of body weight.
Class
DMI, % of body weight
Mature, light work
1.8
Mature, intense work
2.3
Lactating mare with foal, 3 months to weaning
2.0
Two year old, in training
1.9
Once the pounds of dry matter intake are established, the following can be estimated:
1. The percentage of forage and grain in the diet best suited to meet the nutrient demands of a particular horse.
2. The pounds of a feed consumed when the amount is unknown (as illustrated in the pasture example in e. below)
d. Comparing feeds – dry matter basis results should be used for comparing feeds, especially when they vary in dry matter content. Recall that all of the nutrients (protein, carbohydrates, etc.) are contained in the dry matter. The water supplies nothing in terms of nutrient value. Thus, removing water and its dilution effect are essential to make valid comparisons between feeds. Consider the hay and pasture samples below: On an as-sampled basis, the hay appears better in protein. Removing the diluting effect of the water, the dry matter basis results reveal that the nutrient rich dry matter in pasture is superior to the hay.

Hay
Pasture
As Sampled
Dry matter
As Sampled
Dry matter
Moisture, % 10.0 80.0
Dry matter, % 90.0 20.0
DE, Mcal/lb. 0.79  0.88 0.23  1.15
Crude protein, %  8.1 9.0 4.2 21.0
Calcium, % 0.45  0.50  0.16  0.80
Phosphorus, % 0.20  0.22  0.07  0.35

 

e. Estimating individual feed intake – it is often difficult to measure the intake of an individual feed. Pasture is a prime example. You can’t weigh the amount consumed as you can other feeds (hay, grain) because you have no control over how much is offered or consumed. However, if you weigh the amount of hay and grain fed and predict total dry matter intake as described above, the amount of pasture consumed can be estimated.
Example – an 1100 pound horse will consume 20 pounds of total dry matter and is being fed 5 pounds of hay and 5 pounds of grain. The hay and the grain are both 90% dry matter and the pasture is 25% dry matter. With this information, you can estimate the amount of pasture consumed.
1. Calculate the pounds of dry matter consumed from the hay and grain.
Feed
Lbs. fed
%DM Lbs. Dry matter
Hay
5
x
90/100
4.5
Grain
5
x
90/100
+ 4.5
9.0
2. Estimate pounds of pasture dry matter consumed.
Predicted total dry matter intake 20.0
Calculated amounts of other feeds – 9.0
Estimated pasture dry matter intake 11.0
3. Estimate pounds of pasture consumed, as fed.
= (pounds of pasture dry matter consumed)/(dry matter percentage of pasture)
= 11.0/(25/100) = 44 pounds of pasture, as fed.
Thus in a typical day, this horse consumes 5 lbs. of hay, 5 lbs. of grain and 44 lbs. of pasture on an as fed basis.

In Summary:

As sampled basis results:

  • Used for feed tag guarantees.
  • Can be used for evaluating and balancing rations when all feeds offered are similar in dry matter content.

Dry matter basis results:

  • Predicting total feed intake.
  • Estimating individual feed intake.
  • Ration evaluation and balancing when feeds vary in dry matter content.
  • Valid comparison of nutrient value between feed.