The acetyl bromide lignin method accurately quantitates lignin in forage

Abstract

The acetyl bromide lignin (ABL) has been shown to provide a similar relationship between lignin concentration and fiber degradability for grasses and legumes. In contrast, the acid detergent lignin (ADL) method results in different regression equations for grasses and legumes with a larger slope for grasses. The difference may be due to solubilization and loss of lignin in the grasses during the acid detergent fiber (ADF) procedure. While ADL and ABL values for legumes were about the same, ADL values for grasses were about half of those for ABL, supporting the theory that lignin was lost in grasses in the ADL method. We estimated this loss at about 60 %, so multiplying the ADL in grasses by 2.4 would yield the actual lignin concentrations. Applying this multiplier to ADL in grasses, but not in legumes, resulted in analogous regression lines for forage degradability, that were similar to those obtained with the ABL method. The nutritional entity ABL behaves uniformly for grasses and legumes and may properly determine measures of lignin, allowing further research on the mechanisms by which lignin acts as a barrier to enzymatic degradation of forage cell wall polysaccharides, which may provide information on the potential nutritive value of specific plants for herbivores.