|Jung, Hans Joachim
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/1998
Publication Date: N/A
Interpretive Summary: Forages are the primary source of digestible energy and other feed nutrients for dairy and beef production. Fiber represents one-half to two- thirds of the potential digestible energy in forage crops. However, only the carbohydrate portion of the fiber is a source of feed energy for cattle. Lignin is a component of fiber which limits the digestibility of fiber carbohydrates, and lignin is totally non-digestible which means that it cannot provide any feed energy to cattle. Accurate measurement of the amount of lignin in forages is critical for prediction of the potential feeding value of a forage crop. We have demonstrated that the standard method of forage lignin analysis severely underestimates the amount of lignin present in forages. A different method of analysis, commonly used for analysis of lignin in wood, was shown to be much more accurate for the measurement of lignin amount. In the past scientists had considered this wood method to be inappropriate for forage crops. Adoption of the lignin analysis method used for wood to measure lignin in forages will improve the accuracy of our predictions of the digestible energy content of cattle feeds. The improved predictions of feed energy content will increase the efficiency of meat and milk production.
Technical Abstract: An accurate method for estimation of lignin concentration is important to predict the potential digestible energy content of livestock feeds. In this study, the accuracy of lignin concentration estimates based on the Klason lignin and acid detergent lignin methods was evaluated. Ten diverse forage samples were analyzed for crude protein, carbohydrates, lipids, organic acids, ash, lignin (by both methods), and gross energy. The accuracy of lignin concentration estimates of forages was examined by comparing the percentage of the measured forage gross energy that was accounted for in calculation of sample gross energy from compositional analysis. Use of the acid detergent lignin estimate in this calculation accounted for 68 to 84% of the forage gross energy compared to 85 to 97% of the gross energy using Klason lignin. The results indicate that while Klason lignin estimates are substantially higher than acid detergent lignin nestimates, Klason lignin is the more accurate lignin method and does not overestimate lignin because gross energy recoveries were less than 100%.