The influence of the method of determination of lignin on the lignin‐ratio technique for digestibility in the cow

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Abstract
Three methods for the determination of lignin (Norman & Jenkins, Ellis et al. and Armitage et al.) have been compared on samples of food and faeces from eight digestibility trials with lactating cows receiving a diet of hay and concentrates. Details are given of the different values obtained for crude lignin, the nitrogen content of the crude lignin, and lignin corrected for its nitrogen content. The method of Armitage et al. gave the lowest values. The mean digestibility coefficients for crude lignin and corrected lignin respectively, for the three methods in the above‐mentioned order, were 9.3 ± 0.7 and 8.3 ± 0.5, 4.7 ± 0.6 and 9.1 ± 0.7, 1.3 ± 0.8 and 4.4 ± 1.0. Thus lignin as determined by the method of Armitage et al., and expressed as crude lignin, showed a negligible digestibility, which should be acceptable as the basis of a ratio technique for the dairy cow. In a subsequent series of ten digestibility trials with cows on hay‐concentrate diets, and when using this method, the mean digestibility coefficient for crude lignin was ‐ 0.72 ± 0.7.