Identify Cell Wall Factors Limiting Digestibility and Forage Utilization in Sustainable Dairy Farming

CRIS # 3655-21000-033-00D

Timeline: July 14, 2002 to July 13, 2007.

Personnel:
Scientists: John Ralph (1.0), Ronald Hatfield (0.7), Paul Weimer (0.7), David Mertens (0.3), Geneticist (0.3 open position), John Grabber (0.1) Total SY= 3.1
Technical support:
Non-permanent support: Grad Students (3.0); Undergrads (0.75 full time eq.); Assistant Associate Scientists (3)

Importance:
Cell wall components of forages are incompletely digested, reducing energy availability to the animal. Nonrenewable resources (fuel and fertilizer) are wasted in the production of forage cell walls that are not used by the animal, and increased animal wastes are generated because cell walls are not adequately digested. Dairy farming systems would be more sustainable if the factors limiting cell wall digestion were identified and their impacts reduced.

Objectives:
• Characterize plants with genetically modified lignin-pathways to develop novel approaches for improving forage utilization.
• Characterize indigestible residues to identify key factors limiting their digestion.
• Determine the role of rumen environment on digestion kinetics of forage cell walls.
• Develop strategies that include genetic selection to improve rate and extent of cell wall digestion.

Projects:
• Structural characterization of lignin from genetically modified plants to identify potential changes that will increase digestibility of cell walls.
• Determine the role of ferulate cross-linking in grain structure, function and digestibility.
• Determine the role of specific microbial populations and their interactions on cell wall digestion.
• Genetic selection for improved alfalfa stem digestion.

Impact:
Solving the problem of limited cell wall digestibility will result in improved forages with positive economic and environmental impacts. For example a 10% improvement in forage cell wall digestibility by dairy cows in the U.S. would produce $350 million in increased milk and meat production. Equally important is a positive environmental impact of 2.8 million tons less manure solids and no longer a need for 2 million tons of grain supplements.