Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/5/2001
Publication Date: N/A
Citation: Interpretive Summary: Fiber (cell walls) is a critical component of forages and is mainly made up of carbohydrates, protein, and lignin. It provides plants with a framework for normal development. Fiber provides a source of energy for ruminants such as dairy cows and is critical for maintaining good animal health. However, the animal can only utilize the carbohydrate and protein fractions. The lignin fraction limits total digestibility of the fiber. Within a given type of forage the more lignin that is present the less digestible the fiber fraction becomes. Accurate measurements of lignin could be used to predict the digestibility of forages. Rapid methods of lignin determination would aid in the screening of large numbers of forage samples to assess nutrient quality for balancing rations or screening germplasm for selection of improved forages. The acetyl bromide soluble lignin (ABSL) is a rapid method for determining total lignin content in forages. We have developed a convenient procedure for isolating lignin tha can be used as a calibration standard for the ABSL method. This will provide an alternative method for determining lignin that is economical and rapid. The ABSL method may provide a means of accurately predicting nutrient quality of forages to improve forage screening or to maximize nutrient utilization of forages fed in dairy rations. Maximizing forage utilization is a key step in maintaining sustainable dairy farming.
Technical Abstract: Lignin extracted with acidic dioxane was investigated as a possible standard for quantitatively determining lignin content in plant samples using the spectrophotometric method employing acetyl bromide. Acidic dioxane lignins were analyzed for carbohydrate, total protein, nitrobenzene oxidation products, and for UV spectral characteristics. Total carbohydrate econtent of isolated lignins ranged from 2.21 to 5.70%, while protein range from 0.95 to 6.06% depending upon the plant source of the original cell wall sample. Nitrobenzene analysis indicated differences in amount of guaiacyl and syringyl units making up the lignins but this did not alter the UV spectrum of lignin solubilized in acetyl bromide. Regression equations developed for the acetyl bromide method using the isolated lignins for all the plant samples were similar to each other. Lignin values obtained by the acetyl bromide method were similar to the lignin values obtained as acid insoluble residues following a Klason lignin procedure.