Haley Campbell, Lecturer, The Ohio State University ATI
As we get 
closer to spring grazing, we’re itching to put our sheep out to pasture to enjoy the lush growth carpeting the fields. However, at least in the Midwest, we still have a few weeks before pastures are ready to be trodden down by cloven feet. In the meantime, the sheep can get by on hay, stored forages, or grains. But do you know what nutrients are in those feeds? Feed companies already give nutrient contents and those can be found on the feed tag. Forages are another story – visual appraisal can only get us so far. By submitting a forage sample (hay, silage, baleage, fresh pasture, etc.) to an analysis lab, like Rock River, DairyLand Laboratories, DairyOne, and others, we can accurately know what nutrients we can provide to our sheep. When those results come back, they are filled with a plethora of terms and acronyms that can be difficult to interpret without any background knowledge. Below, I’ve picked a few that are usually the most important to know and understand.
Dry Matter (DM)– the amount of feed in feed! It is the percent of nutrients left behind after all moisture/water has been removed from the feed. This is what all other nutrient percentages are based on. Dry matter is used for diet formulations to eliminate the variability of moisture in feeds.
As Fed (AF) – Sometimes written “as-is” or “as provided;” this is the feed as you would offer it to the animal and contains all moisture.
Crude Protein (CP) – the total protein in the feed based on the percent nitrogen as determined in the lab.
Neutral Detergent Fiber (NDF) – The full fiber fraction of the feed that includes cellulose, hemicellulose, and lignin which are found in the cell wall of plants. NDF is an indicator of intake; more NDF, less intake. Grasses should have an NDF no more than 55% and legumes no more than 45%.
Acid Detergent Fiber (ADF) – A portion of the NDF and only includes cellulose and hemicellulose and estimates digestibility.
Lignin – The indigestible portion of fiber that increases the “woodiness” of a plant. Lignin will increase as plants get older (more mature) to provide more support and structure to a larger plant. If a forage has more lignin, it is not as digestible.
Non-Fiber Carbohydrate (NFC) or Non-Structural Carbohydrate (NSC) – The starches, sugars, and pectin found in a plant. This value indicates the amount of quickly digestible/fermentable nutrients in the feed. Greater NFC/NSC means there is more energy in that feed.
Neutral Detergent Fiber Digestibility (NDFD) – How much NDF is digested after a set amount of time; usually 48, 72, 12, or 240 hours. This shows how much fiber can be digested in the rumen of the animal. Usually the 48-hour value is referenced when discussing feed quality. The greater the value, the more digestible. Animals will be able to get more nutrients from that feed.
Undigestible Neutral Detergent Fiber (uNDF) – The amount of fiber that is unable to be digested after 240 hours (10 days).
Total Digestible Nutrients (TDN) – The portion of nutrients that can actually be digested and used by the animal. Hopefully very high!
Net Energy for Maintenance, Lactation, or Gain (NEM, NEL, NEG) – The amount of energy that can be used for maintenance of the animal, milk production, or gain (for finishing or growing animals)
For more information, check out:
Oklahoma State University: Forage Quality Interpretations – https://extension.okstate.edu/fact-sheets/forage-quality-interpretations.html
List of National Forage Testing Association Certified Labs – https://www.foragetesting.org/_files/ugd/24f64f_3e42dad1cfd74595979b18d9e3e3ed63.pdf