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.
Moisture % – the percentage of water in the sample.
Dry Matter % – everything in the sample other than water including protein, fiber, fat, minerals, etc. Find by subtracting moisture % from 100.
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.
As sampled results can be simply converted to dry matter basis results and vice versa using the following formulas.
As sampled basis to dry matter basis
Dry matter basis= As sampled basis / (DM% / 100)
A pasture sample that has a DM% of 25 and an as sampled crude protein % of 4.0. To find the percentage of crude protein on a dry matter basis:
Crude protein %, DM basis = 4.0 / (25 / 100) = 16.0%
Dry matter basis to as sampled basis
As sampled basis = dry matter basis x (DM% / 100)
A hay sample that has a DM% of 90 and a dry matter basis crude protein % of 12.0. To find the percentage of crude protein on an as sampled basis:
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.
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.
Dry Matter Results
- 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.
- 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:
- 22.2 lbs. of hay @ 90% dry matter = 2.2 lbs. of water + 20 lbs. of dry matter.
- 80 lbs. of pasture @ 25% dry matter = 60 lbs. of water + 20 lbs. of dry matter.
- To consume the same pounds of nutrient rich dry matter (20 lbs.), horses need to eat larger amounts of pasture.
- Predicting feed intake – Total dry matter intake (DMI) is based on body weight, stage of growth, reproductive status and level of activity. DMI is expressed as a percentage of body weight. The table below lists a couple of examples.
|Class||DMI, % of body weight|
|Mature. Light work||1.8|
|Mature, intense work||2.3|
|Lactacting mare with foal (3 months to weaning)||2.0|
|Two year old, in training||1.9|
Once the pounds of DMI intake are established, you can estimate the percentage of forage or grain best suited to meet the nutrient demand of a particular horse. You can also estimate the pounds of feed consumed when the amount is unknown (see below).
- Comparing feeds – Dry matter basis results should be used for comparing feeds, especially when they vary in dry matter content. Nutrients (protein, carbohydrates, etc.) are contained in the dry matter only. 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.
|As Sampled||Dry Matter||As Sampled||Dry Matter|
|Dry matter, %||90.0||20.0|
|Crude protein, %||8.1||9.0||4.2||21.0|
- 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.
A 1,100-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 hay and grain:
- 5 lbs of hay x 90/100 DM = 4.5 lbs dry matter from hay
- 5 lbs of grain x 90/100 DM = 4.5 lbs dry matter from grain
- 9 lbs of total DMI from hay and grain
2. Estimate pounds of pasture dry matter consumed:
- 20 lbs of predicted total DMI – 9 lbs total DMI from hay and grain = 11 lbs estimated pasture DMI
3. Estimate pounds of pasture consumed, as fed:
- 11 lbs pasture DMI / (25/100 DM) = 44 lbs of pasture, as fed