Lignin studies III. Lignin as tracer in digestibility investigations

Abstract

The suitability of lignin as a tracer substance, i.e. the apparent indigestibility of lignin, is dependent on the method used for the determination of lignin. Further, a method suitable for one food is not necessarily suitable for all kinds of food. By the method used in this investigation (method A) the mean digestibility of lignin from mature hay or from hay cured after blooming was found to be +1.8 ± 0.6 %. However, the mean digestibility of lignin from hay cut at an early stage of growth was +17.6 ± 1.0 %. When a pepsin pretreatment was included in the method (method B) the digestibility of crude lignin was found to be somewhat lower than the digestibility of lignin. The lignin determined by method A is more suitable for the lignin ratio technique (digestibility coefficient +1.8 ± 0.7. than the crude lignin determined by method B (digestibility coefficient +3.1 ± 0.9). The lignin preparations isolated from hay and from corresponding faeces have not a uniform composition. Appreciable differences appear in the methoxyl and in the nitrogen contents.