Can lignin and monomer composition of fibre describe the variation in iNDF in forages?

Abstract

Indigestible NDF (iNDF) is an entity in feed evaluation systems. In this study, iNDF is defined as the portion of NDF not digested after 288 h of rumen incubation in Dacron bags with 12 µm pore size. However, the method is resource demanding. The objective of this study was to elucidate the effect of lignin and hemicellulose monomers on iNDF variation within and among forage types and their ability to predict iNDF variation in linear and multiple regression models. The hypotheses were 1) lignin is expected to have high ability in describing the iNDF variation and 2) the inclusion of hemicellulose monomers will increase this ability. iNDF was determined on 50 grass-clover silages and 50 whole crop maize silages as well as 40 maize stem and 10 maize ear samples. All samples were analysed for neutral detergent fibre (NDF), Klason lignin (KL), cellulose and non-cellulose polysaccharides (NCP). Grass-clover and whole crop maize silages were analysed for acid detergent lignin (ADL). Lignin variables had the most consistent correlation to the iNDF variation throughout both correlation and regression analyses. Arabinose also showed high correlations and relationships in linear regression to iNDF and almost at same level as lignin variables. Multiple linear regression increased the accuracy for grass-clover silage and combined analysis with all forage types, with KL and/or ADL as first explanatory variables. However, the increase in accuracy is not consistent between forage types.