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.
Highlights
Than the crude lignin determined by method
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
Summary
Csonka et al [5] report that 37 % of the methoxyl groups of a lignin preparation obtained from corn cobs by the alkali method, disappeared in the digestive tract of a cow. In the experiments of Ely et al the lignin in hay and corresponding faeces differs only a little in its methoxyl content yet they have taken the digestibility of lignin into account in the calculation. The method A is useful for the lignin ratio technique in investigations concerning mature hay or hay cured after blooming, which contains lignin about 7 % or more. If the lignin content of the food is below 6 % ,it is convenient to establish the validity of the method with a digestion trial
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