Relationship between stalk cell wall digestibility and fibre composition in maize

Abstract

AbstractThe stalk fraction of recombinant inbred lines of maize (RILs), harvested shortly before silage stage, was used to determine genetic variation for organic matter digestibility (OMD) and cell wall digestibility (CWD) as well as variation for fibre content (eg neutral (NDF) and acid detergent fibre (ADF)) and chemical composition (eg hemicellulose, cellulose, lignin, total phenolics and the phenolic acid esters: p‐coumaric, ferulic and vanillic acid). OMD and CWD, as monitored in an in vitro incubation using rumen fluid, ranged between 64.6 and 80.7% and 44.9 and 63.0%, respectively. The fibre content varied from 460 to 675 g kg−1 dry matter (NDF) and from 258 to 405 g kg−1 dry matter (ADF). Generally, hemicellulose (HEM) was present in lower amounts in the cell wall than cellulose (CEL). Comparison of two subsets of the RILs with either a low or a high CWD demonstrated that the RILs with the low CWD contained higher concentrations of fibre and enhanced amounts of all cell wall constituents measured except for HEM and ferulic acid (Fa). The Fa content of the low CWD subset was lower and no significant subset difference was present for HEM. The correlations between two blocks in a field trial (repeatability) was high for all forage quality traits, except HEM, total phenolics (tPHEN), p‐coumaric acid and vanillic acid. A close negative relationship existed between OMD and NDF, ADF, CEL and permanganate lignin (pLIG) showing absolute correlation coefficients above r = 0.80. The association of CWD to these cell wall properties was either weak or moderate. In contrast to all other cell wall constituents, tPHEN correlated better to CWD than to OMD (r = −0.82 and −0.62, respectively). By means of multiple regression, a regression equation was generated for CWD and OMD using ASH, pLIG and tPHEN or ASH, NDF, pLIG and tPHEN, respectively, as explanatory variables. About 92% of the variation of OMD and 80% of the variation of CWD could be explained by these regression models with residual standard deviations of 1.37% and 2.19%, respectively.