Horse Hay Analysis: Dry Matter vs. ‘As Sampled’ or ‘As Fed’

While nutritionists working with ruminants tend to focus on the nutrient content of feeds on a dry matter basis, in equine nutrition we mostly focus on the as-fed value of nutrients.
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Horse Hay Analysis: Dry Matter vs. ‘As Sampled’ or ‘As Fed’
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

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Written by:

Clair Thunes, PhD, is an equine nutritionist who owns Clarity Equine Nutrition, based in Gilbert, Arizona. She works as a consultant with owners/trainers and veterinarians across the United States and globally to take the guesswork out of feeding horses and provides services to select companies. As a nutritionist she works with all equids, from WEG competitors to Miniature donkeys and everything in between. Born in England, she earned her undergraduate degree at Edinburgh University, in Scotland, and her master’s and doctorate in nutrition at the University of California, Davis. Growing up, she competed in a wide array of disciplines and was an active member of the U.K. Pony Club. Today, she serves as the district commissioner for the Salt River Pony Club.

One Response

  1. Just took my gelding to las vegas to vet and he had a very swollen sheath and over weight and the vet took him off bermuda hay. My question is what mix could i give him with low sugar? The vet took him off his safe choice low sugar pellets too. His weight was 1300 lbs. He’s a mustang. They did do all blood work cleaned the sheath and put camera up the sheath to check. All blood work came back ok but sugar was spiked some.

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