ARS | Publication request: Forage digestibility: the intersection of cell wall lignification and plant tissue anatomy

Submitted to: International Advances in Ruminant Nutrition Research in Brazil
Publication Type: Proceedings
Publication Acceptance Date: December 17, 2010
Publication Date: March 24, 2011
Citation: Jung, H.G. 2011. Forage digestibility: the intersection of cell wall lignification and plant tissue anatomy. In: III International Symposium Advances on Research Techniques for Ruminant Nutrition, March 24-25, 2011, Pirassununga, Brazil. p. 137-160.

Technical Abstract: Cellulose and the other polysaccharides present in forage cell walls can be completely degraded by the rumen microflora but only when these polysaccharides have been isolated from the wall and all matrix structures eliminated. Understanding how cell wall component interactions limit microbial degradation of the polysaccharides is critical. Our understanding of the factors that impact cell wall degradation of forages has improved dramatically in recent years. The old rule that immature forages are the most digestible is still correct, but now we can explain why digestibility declines with forage maturation. I believe that this understanding offers new opportunities to select and develop forages with greater cell wall degradability. Most of these opportunities are as yet unproven and will require significant effort to validate and implement, but the potential improvements will be worth the effort. Yes, lignin is the most important factor that limits cell wall degradation; however, it is through an understanding of the details of forage lignification and how this impacts the process of degradation that forage quality will be improved. My objective is to integrate knowledge of cell wall composition and structure, plant and tissue anatomy, and developmental patterns during cell and plant maturation as these factors influence the degradation of forage cell wall material in the rumen. I will review our understanding of plant cell wall chemistry and anatomy, and highlight the similarities and differences between grass and legume forages. This information will then be used as a basis for understanding the rate and extent of forage cell wall degradation in the rumen. Finally, I will propose some avenues for improving the digestibility of forages based on these concepts.