HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Akin, D. E. Search for Related Content PubMed Articles by Akin, D. E. Agricola Articles by Akin, D. E.

Histological and Physical Factors Affecting Digestibility of Forages

Richard B. Russell Agric., Res. Center, ARS-USDA, P.O. Box 5677, Athens, GA 30613.

^* Corresponding author.

Factors that limit forage quality are complex and interactive. Structural characteristics that limit forage breakdown are primarily highly lignified support tissues like sclerenchyma and xylem. However, the presence of chemical barriers (likely the low molecular weight phenolic compounds) within "living" cell walls, such as the parenchyma bundle sheath and epidermis, prevents fiber degradation in these tissues. The presence of high proportions of these tissues in leaves of warm-season grasses plus growth in hotter climates, which tends to speed maturity, combine to limit breakdown of warm-season grass leaves compared to cool-season species. Legume leaflets in warm- and cool-season species can be readily degraded due to a high proportion of mesophyll. However, leaflets of certain species or cultivars with high tannin concentrations are poorly degraded, with mesophyll and vascular bundles comprising the residue. Grass stems have a more rigid structure than leaves, with the non-digestible epidermis, sclerenchyma ring, and vascular tissue occupying about 30% of the tissues in the cross sections. In addition, mature grass stems have a poorly degraded parenchyma that contributes to a rigid structure in the residue. Parenchyma in legume stems is totally degraded, leaving a residue of a hollow cylinder surrounded by a uniformly lignified ring. Possibly, variations between structures of mature grass and legume stems contribute to observed differences in forage quality for these forage types. Rumen bacteria and fungi both physically associate with the more recalcitrant forage tissues. Fungi are better able to colonize the liguocellulosic tissues and can partially degrade the most resistant xylem tissues. Research avenues for improving forage quality are: (i) to enhance the ability of anaerobic fungi to weaken lignocellulosic barriers, (ii) to reduce the amount of non-degradable barriers, particularly in stems, by plant breeding, and (iii) to improve by plant breeding the rate and extent of slowly or partially degraded tissues in leaves.

Received for publication December 4, 1987.

This article has been cited by other articles:

				D. C. Olk Improved Analytical Techniques for Carbohydrates, Amino Compounds, and Phenols: Tools for Understanding Soil Processes Soil Sci. Soc. Am. J., October 30, 2008; 72(6): 1672 - 1682. [Abstract] [Full Text] [PDF]

				H. G. Jung and M. D. Casler Maize Stem Tissues: Cell Wall Concentration and Composition during Development Crop Sci., June 20, 2006; 46(4): 1793 - 1800. [Abstract] [Full Text] [PDF]

				J. W. MacAdam and H. F. Mayland The Relationship of Leaf Strength to Cattle Preference in Tall Fescue Cultivars Agron. J., March 1, 2003; 95(2): 414 - 419. [Abstract] [Full Text] [PDF]

				W. Darmosarkoro, M. M. Harbur, D. R. Buxton, K. J. Moore, T. E. Devine, and I. C. Anderson Growth, Development, and Yield of Soybean Lines Developed for Forage Agron. J., September 1, 2001; 93(5): 1028 - 1034. [Abstract] [Full Text] [PDF]

				L.E. Trenholm, R.N. Carrow, and R.R. Duncan Mechanisms of Wear Tolerance in Seashore Paspalum and Bermudagrass Crop Sci., September 1, 2000; 40(5): 1350 - 1357. [Abstract] [Full Text]

				G.F. da C. Lima, L.E. Sollenberger, W.E. Kunkle, J.E. Moore, and A.C. Hammond Nitrogen Fertilization and Supplementation Effects on Performance of Beef Heifers Grazing Limpograss Crop Sci., November 1, 1999; 39(6): 1853 - 1858. [Abstract] [Full Text]

				K. Inoue, V. J.H. Sewalt, G. Murray Ballance, W. Ni, C. Stürzer, and R. A. Dixon Developmental Expression and Substrate Specificities of Alfalfa Caffeic Acid 3-O-Methyltransferase and Caffeoyl Coenzyme A 3-O-Methyltransferase in Relation to Lignification Plant Physiology, July 1, 1998; 117(3): 761 - 770. [Abstract] [Full Text]

				D. R. Buxton and D. D. Redfearn Plant Limitations to Fiber Digestion and Utilization J. Nutr., May 1, 1997; 127 (5): 814S - 814S. [Abstract] [Full Text] [PDF]