When we feed hay and other feeds, such as commercial grains, the form we feed them in contains some amount of water. The amount of water present directly impacts that feed’s nutrient content. | Photo: iStock

Q. I recently received a hay analysis for the hay I purchased, and the results are in two columns. One is headed “dry matter” and the other “as sampled.” What do these mean, and which numbers should I be looking at?

A. When we feed hay and other feeds, such as commercial grains, the form we feed them in contains some amount of water. The amount of water present directly impacts that feed’s nutrient content. The more water, the lower the amount of other nutrients per pound. Feed in this form is referred to as being “as fed” or “as sampled,” meaning in the form that we feed it, including water.

Dry matter is the part of the feed that does not contain any water. We can determine the water content of feeds and, by subtraction, the dry matter using several methods. Typically, they involve weighing a known amount of ground feed into a small dish and heating it in an oven at a temperature between 65 and 135 degrees Celsius (150 to 275 F) for two to 20 hours, until the sample reaches a constant weight. The sample is then placed in a desiccator to prevent it from absorbing moisture from the atmosphere as it cools. The final sample is reweighed, and the difference in the sample’s weight at the end of this process compared to the start is the amount of water the feed contained, which can be determined as a percentage. The percentage of dry matter in the sample can then be calculated by subtracting the percent water from 100