Crude protein (CP): Laboratories measure the nitrogen (N) content of the forage and calculate crude protein using the formula: CP = % N x 6.25. Crude protein will include both true protein and nonprotein nitrogen. Cattle can use both types to some degree. Crude protein values give no indication if heat damage has occurred, which may alter protein availability.
Acid detergent fiber (ADF): This value refers to the cell wall portions of the forage, which are made up of cellulose and lignin. These values are important because they relate to the ability of an animal to digest the forage. As ADF increases, digestibility of a forage usually decreases.
Neutral detergent fiber (NDF): The NDF value is the total cell wall, which is composed of the ADF fraction plus hemicellulose. Neutral detergent fiber values are important in ration formulation because they reflect the amount of forage the animal can consume. As NDF percentages increase, dry matter intake will generally decrease.
Lignin: It is the prime factor influencing the digestibility of plant cell wall material. As lignin increases, digestibility, intake, and animal performance usually decrease.
Total digestible nutrients (TDN): It is the sum of the digestible fiber, protein, lipid and carbohydrate components of a feedstuff or diet. It is directly related to digestible energy and is often calculated based on ADF.
This information accompanies the article on "Evaluation of Three Bermudagrass Hybrids for Grazing and Hay Production in South Louisiana" by Guillermo Scaglia, Associate Professor, Iberia Research Station, Jeanerette, La. Go to the article.
The LSU AgCenter and the LSU College of Agriculture