Relationship between stalk cell wall digestibility and fibre composition in maize

Abstract

Abstract:The 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 675gkg-' dry matter (NDF) and from 258 to 405gkg-' 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), pcoumaric acid and vanillic acid. A close negative relationship existed between OMD and NDF, ADF, CEL and permanganate lignin (pLIG) showing absolute correlation coeffcients 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.

Lax leaf maize: cell wall composition and nutritional value

“…Arabinose, the site of cross-linking between lignin and arabinoxylan, could provide more opportunity for cross-linking and therefore have a negative relationship with digestibility. Although PCA is not believed to be involved in cross-linking between lignin and hemicellulose, 34 other authors have also reported a negative relationship between PCA concentration and digestibility in maize, 17,35 perhaps because low PCA is not independent of low lignin.…”

“…However, the fraction of total FA that is esteri®ed to arabinose but not bound to lignin, ie not involved in cross-linkage, does not inhibit degradation and need not be negatively correlated with digestibility. 37 Although multiple regression models arrived at by Marvin et al 35 indicated that total phenolics had a signi®cant negative relationship with digestibility, Jung et al 38 found that the partial regression coef®cients for prediction of polysaccharide component degradability in maize were negative or non-signi®cant for etheri®ed FA and non-signi®cant for esteri®ed FA. Furthermore, preliminary data for the materials analysed in Experiment 1 indicate that the fraction of total FA that is ester-linked only is onehalf to three-quarters of the total alkali-extractable FA (data not shown), as was also observed for other maize inbreds 17 and hybrids.…”

Relationship of cell wall composition toin vitro cell wall digestibility of maize inbred line stems

“…This variable was found to be negatively related to cell wall digestibility, in agreement with previous results. 4,35,42,43 The fact that NDF content affects NDF digestibility may express the in¯uence of cell wall aging on ®bre degradability. The various genotype samples harvested at the same dry matter content stage might nevertheless differ in the maturation stage of the cell walls.…”

Relationship between Phenolic Acids Formed During Rumen Degradation of Maize Samples and in vitroDigestibility

“…The amount of PCA and FA esters in the maize samples was determined by HPLC as described before (Marvin et al 1995).…”