|VAN SOEST, PETER - Cornell University - New York|
|ROBERTSON, JAMES - Cornell University - New York|
|Hall, Mary Beth|
|BARRY, MICHAEL - Agmodels Foundation, Inc|
Submitted to: British Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2020
Publication Date: 5/14/2020
Citation: Van Soest, P.J., Robertson, J.B., Hall, M., Barry, M.C. 2020. Klason lignin is a nutritionally heterogeneous fraction unsuitable for prediction of neutral detergent fiber digestibility in forages. British Journal of Nutrition. https://doi.org/10.1017/S0007114520001713.
Interpretive Summary: Estimating the digestibility of fiber in ruminant diets is important for predicting how well a diet will meet the nutrient requirements of the animal. "Lignin" is an indigestible portion of fiber that has been used to estimate fiber digestibility. However, it had not been resolved which of two different measurements for lignin, Klason lignin or acid detergent lignin (ADL), was best for predicting fiber digestibility. Closer evaluation of Klason lignin compared to ADL showed that Klason lignin contained at least two different fractions, one of which was related to increasing fiber digestibility, whereas ADL was consistently associated with reduced fiber digestibility. Based on this work, ADL is the more appropriate lignin measure to estimate fiber digestibility for ruminant diets. This is important for more accurate formulation of diets to meet animal nutrient requirements to support good production and minimize waste.
Technical Abstract: Although lignin has been negatively correlated with fiber digestibility (NDFD), the selection of an analysis, Klason lignin (KL) or acid detergent lignin (ADL), to describe the nutritionally relevant lignin has not been resolved. Dismissed as an artifact in this discussion is the nutritional behavior of the difference between KL and ADL (KL – ADL = delta L). Our objective was to evaluate delta L and explore its relationship with NDFD relative to KL and ADL in order to define the homogeneous or heterogeneous nature of KL. Data sets from 2 laboratories (DS1, DS2) were used that included ADL and KL as percentages of dry matter, and in vitro NDFD at 48 h (NDFD48; percentage of neutral detergent fiber). DS1 contained 7 C3 grasses, 17 C4 forages (13 corn plants, 4 corn silages) and 19 alfalfa hays, and DS2 had 15 C3 grasses, 8 C4 forages, and 6 alfalfa samples. Regression, correlation, and t-test analyses were applied within forage type within data set. Mean delta L was greater than ADL in C3 and C4 samples, and less in alfalfas. delta L was not correlated with NDFD48. Correlations of NDFD48 with KL varied from positive to negative though only negative correlations were significant, and ADL was negatively correlated excepting for alfalfas in DS2. ADL was more consistently negatively correlated with fiber digestibility than was KL. Increasing delta L as a proportion of KL was positively correlated with NDFD48 in C3 and C4 samples. The differing behaviors of delta L and ADL relative to NDFD48 indicate that KL is a nutritionally heterogeneous fraction, the behavior of which may vary by forage type and ratios of ADL and delta L present.