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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. The important point
is to be consistent . 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.
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| A. |
Definitions
Moisture % = the percent water in the sample. |
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Dry
Matter % = 100% - Moisture%. The dry matter (DM) represents
everything in the sample other than water including protein,
fiber, fat, minerals, etc. |
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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. |
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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. |
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| B. |
Conversions
- as sampled results can be simply converted
to dry matter basis results and vice versa using
the following formulas. |
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| 1. |
As
sampled basis to dry matter basis: |
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Dry
matter basis = As sampled basis/(DM%/100)
Example: Pasture |
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Crude
Protein %
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DM%
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As
sampled
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DM
Basis
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25 |
4.0
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Crude
Protein %, DM basis = 4.0 / (25/100) = 16.0% |
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| 2. |
Dry
matter basis to as sampled basis: |
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As
sampled basis = Dry matter basis x (DM%/100)
Example: Hay |
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Crude
Protein %
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DM% |
As
sampled
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DM
Basis |
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90 |
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12.0
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Crude
Protein %, As sampled = 12.0 x (90/100) = 10.8% |
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| C. |
Uses |
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| 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. |
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| 2. |
Dry
Matter Results |
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| 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. |
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| 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: |
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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.
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| 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. |
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Table.
1. Predicted dry matter intake (DMI) as a percentage
of body weight. |
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| Class |
DMI,
% of body weight |
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| Mature,
light work |
1.8 |
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| Mature,
intense work |
2.3 |
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| Lactating
mare with foal, 3 months to weaning |
2.0 |
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| Two
year old, in training |
1.9
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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) |
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| 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 it's dilution effect are essential
to make valid comparisons between feeds. Consider the
hay and pasture samples below: |
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Hay |
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Pasture |
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As
Sampled |
Dry
matter |
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As
Sampled |
Dry
matter |
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| Moisture,
% |
10 |
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80 |
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| Dry
matter, % |
90
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20 |
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| DE,
Mcal/lb. |
0.79 |
0.88 |
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0.23 |
1.15 |
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| Crude
protein, % |
8.1
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9.0 |
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4.2 |
21.0 |
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| Calcium,
% |
0.45 |
0.50 |
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0.16 |
0.80 |
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| Phosphorus,
% |
0.20
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0.22 |
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0.07 |
0.35 |
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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. |
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| 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. |
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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. |
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| 1. |
Calculate
the pounds of dry matter consumed from the hay
and grain. |
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| Feed |
Lbs.
fed |
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%DM |
Lbs.
Dry matter |
| Hay |
5 |
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x |
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90/100 |
4.5 |
| Grain |
5 |
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x |
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90/100 |
+ 4.5 |
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9.0 |
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| 2. |
Estimate
pounds of pasture dry matter consumed. |
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Predicted
total dry matter intake |
20.0 |
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Calculated
amounts of other feeds |
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9.0 |
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Estimated
pasture dry matter intake |
11.0 |
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| 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. |
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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. |
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summary: |
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As
sampled basis results:
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- Used
for feed tag guarantees.
- Can
be used for evaluating and balancing rations when all
feeds offered are similar in dry matter content.
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Dry
matter basis results: |
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- 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.
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