|Barros-Rios, Jaime -|
|Santiago, Rogelio -|
|Malvar, Rosa -|
|Jung, Hans Joachim|
Submitted to: Animal Feed Science And Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 11, 2012
Publication Date: March 30, 2012
Citation: Barros-Rios, J., Santiago, R., Malvar, R.A., Jung, H.G. 2012. Chemical composition and cell wall polysaccharide degradability of pith and rind tissues from mature maize internodes. Animal Feed Science and Technology. 172(3-4):226-236. Interpretive Summary: Corn silage is a major feed resource for cattle throughout the world. Unfortunately, the stover portion of corn silage is high in fiber content and this fiber is of limited digestibility. Plant geneticists are working to develop corn varieties with more digestible fiber; however, progress has been limited because of insufficient knowledge of the factors that limit corn fiber digestion and amount of genetic variation in corn for fiber characteristics. Variability in fiber amount, fiber composition, and fiber digestibility of six corn inbred lines, related to the parent inbreds used for commercial hybrid development, were studied. The pith tissue found in the center of corn stalks was found to contain less total fiber, the fiber had a different chemical composition, and the fiber was more digestible than for the rind tissue that forms the exterior layer of corn stalks. The corn inbreds differed from each other in fiber concentration, composition, and digestibility of the pith and rind tissues. Specific chemical entities in the corn stalk fiber were identified that could be used to predict digestion potential of the fiber. These results will assist corn geneticists in selecting criteria for breeding and genes to target in order to speed progress in developing more digestible corn silage varieties.
Technical Abstract: This study was undertaken to identify tissue-specific biochemical traits that may be targeted in breeding programs for improving forage digestibility. We compared cell wall chemical composition and 24- and 96-h in vitro degradabilities in separated pith and rind tissues of the fourth above-ground internode from six maize (Zea mays L.) inbred lines. Across genotypes rind tissues had higher total cell wall, ferulate ethers, and Klason lignin concentrations (69%, 53%, and 6% higher, respectively), and were less degradable and the increased degradation between incubation times were larger than in pith tissues. Genotypes exhibited genetic variation for most cell wall components and for all measures of cell wall degradability. However, none of genotypes had extreme values for these cell wall traits in both tissues, indicating that regulation of cell wall characteristics may be tissue-independent. Cross-linking of lignin to arabinoxylan through ferulate ethers explained a portion of cell wall degradability variation in both tissues (55% and 24% of pith and rind cell wall 24-h degradability, respectively) and in conjunction with Klason lignin concentration appeared to be one of the major determinants of cell wall degradability. p-Coumarate ester and glucose concentrations were the overall best predictors of pith cell wall degradability, and arabinose concentration was a good indicator of rapid rind cell wall degradability, suggesting the potential usefulness of these cell wall traits in breeding programs aimed at improved cell wall digestibility. However, the majority of rind cell wall degradability variation (65% and 73% of 24- and 96-h degradabilities, respectively) was not explained by the cell wall traits evaluated. Additional biochemical traits and anatomical factors influence cell wall degradation in isolated cell types.