Digestibility of silages in relation to their hydroxycinnamic acid content and lignin composition

The effectiveness of the analysis of cell wall-bound hydroxycinnamic acids and the composition of lignin to evaluate the in vivo digestibility of a silage collection with unknown botanical composition was evaluated.

Syringyl units content and total etherified phenols showed the highest correlation coefficients with in vivo dry matter digestibility (IVDMD) (r = - 0.792 and r = - 0.703, respectively), while guaiacyl units and total phenols showed the highest correlation coefficients with in vivo organic matter digestibility (IVOMD) (r = - 0.871 and r = - 0.817, respectively). Using the above-mentioned chemical parameters, 10 equations were also developed to predict in vivo digestibility. The prediction of IVDMD produced a high adjusted R(2) value (0.710) using syringyl, total lignin, etherified total phenols, esterified ferulic acid and total phenol content as predictors. The prediction of IVOMD produced a higher adjusted R(2) value (0.821) using guaiacyl, total phenols, total ferulic acid and etherified p-coumaric acid content as predictors.

Cell wall digestibility depends on a multiplicity of factors and it is not possible to attribute a causal effect on in vivo digestibility to any single factor. However, syringyl and guaiacyl content and etherified phenols emerge as good predictors of digestibility.