CORRELATION OF ACID DETERGENT LIGNIN AND KLASON LIGNIN WITH DIGESTIBILITY OF FORAGE DRY-MATTER AND NEUTRAL DETERGENT FIBER

The acid detergent lignin and Klason lignin methods were compared for their correlation with forage digestibility. Thirty-six forages, inclu ding C-3 legumes and C-3 and C-4 grasses, were analyzed for sulfuric a cid detergent lignin, Klason lignin, and in vitro digestibilities of d ry matter (DM) and neutral detergent fiber (NDF). Twenty of these fora ges were also fed to lambs at restricted intake for measurement of DM and NDF digestibilities. Lignin concentrations determined by the two l ignin methods were positively correlated, and the Klason lignin value was always greater than the acid detergent Lignin concentration. The l argest differences were observed for grass forages. Digestibilities of forage DM and NDF were negatively correlated with both lignin methods for the in vitro system and the lamb digestibility trials. The degree of correlation for the two lignin methods with digestibility was gene rally similar across all forages and within forage classes. Slopes of linear regressions of digestibility on lignin concentration did not di ffer between legumes and grasses. Although the sulfuric acid detergent lignin and Klason lignin procedures gave very different estimates of forage lignin concentration, they were similarly correlated with diges tibility and should yield predictions of forage digestibility that hav e similar accuracy.