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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #84234
Title: DEGRADABILITY OF CELL-WALL POLYSACCHARIDES IN MAIZE INTERNODES DURING STALKDEVELOPMENT

Author
item Jung, Hans Joachim
item MORRISON, TERESA - AUBURN UNIVERSITY
item Buxton, Dwayne

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Corn silage is one of the most important feed resources used in dairy cow feeding. Current recommendations to farmers concerning which corn hybrid to grow for silage are based primarily on the amount of grain produced. This system ignores the rest of the corn plant which comprises 50% or more of the silage. The vegetative part of corn plants is high in fiber, which is poorly digested by dairy cattle. Breeding for improved fiber digestibility of corn plants is hampered by limited understanding of the factors which account for the low digestibility of fiber. In this study we examined the development of the fiber fraction in the corn stalk. It was found that events very early in development were strongly related to fiber digestibility, but that these important factors were difficult to identify in more mature corn plants. Of particular importance was formation of chemical cross-links between the potentially digestible carbohydrates in fiber with lignin, the fiber fraction which prevents digestion. Our results indicate that breeding for reduced fiber cross-linking to improve digestibility of corn silage will be very difficult because of when in plant development this trait can be observed. We suggest that this trait may be more effectively altered through biotechnology because traditional plant breeding is unlikely to be successful. Plant improvement organizations involved in biotechnology could improve corn silage feeding value by reducing the activity of the genes responsible for formation of cross linking in fiber.

Technical Abstract: Limitations to degradation of forage cell-wall constituents in maturing plant tissue are not fully understood, which limits progress in developing cultivars with improved digestibility. We determined in vitro degradability of cell wall components in developing internodes of maize (Zea mays L.). Plants were grown in the growth chamber and harvested at the 15th leaf stage of development. Individual internodes were divided in half and separated into rind and pith tissues. Cell wall degradability was measured on the internode samples and correlated to cell wall composition. Degradability of all wall polysaccharide components, except galactose and mannose, declined with maturation of maize internodes. Degradabilities of glucose and xylose residues exhibited large differences between 24- and 96- h fermentation intervals (31 to 58% additional degradation in 72-h), whereas potentially degradable arabinose and uronic acids were almost completely degraded in 24-h. Maize rind, consisting of sclerenchyma tissu and vascular bundles, was less degradable than the pith (736 vs. 811 g/kg, respectively), which had thinner walled parenchyma tissue and fewer vascular bundles. Lower portions of internodes were younger and more degradable than the upper halves (805 vs. 743 g/kg, respectively). Ferulate ether concentration was negatively correlated with cell wall polysaccharide degradability in young, elongating internodes but not for internodes in which elongation had ceased to occur. This pattern was in agreement with the hypothesis that ferulate cross-linking limits wall degradation, but that the effect is only observable in young tissues before dilution of ferulate ether concentrations by secondary wall deposition of lignin and polysaccharides obscures the relationship.