Project Number: 3655-21000-055-00
Project Type: Appropriated

Start Date: Jan 25, 2013
End Date: Jan 24, 2018

Objective:
Objective 1: Increase profitability, improve animal welfare and reduce manure production by improving the digestibility and energy conversion efficiency of forages in dairy rations by manipulating forage cell-wall biosynthetic pathways to lower indigestible residue formation, lower waste production, and develop more efficient tools for evaluating forage quality. Sub-Objective 1.1: Use genetic manipulation of biosynthetic pathways (e.g., lignin, lignin modifications, lignin cross-linking, ferulate cross-linking, structural polysaccharides) to identify avenues for altering cell wall digestibility and the formation of indigestible residues. Sub-Objective 1.2: Develop methods to provide rapid screening of plant materials for chemical characteristics related to improved energy conversion efficiency and/or other nutrient quality factors. Objective 2: Increase profitability and reduce the amount of nitrogen-containing wastes that enter the environment by reducing protein loss during the post-harvest storage and livestock consumption of alfalfa and other forages through manipulation of forage phenolic metabolic pathways. Sub-Objective 2.1: Gain knowledge of factors that influence accumulation of hydroxycinnamyl-conjugates (e.g., phaselic acid, clovamide, chlorogenic acid) utilizable by PPO systems in forages with respect to efficacy in post-harvest proteolytic inhibition, as well as combating abiotic stress (UV, ozone). Sub-Objective 2.2: Determine the chemical basis for proteolytic inhibition caused by classes of tannins and polyphenol oxidase generated o-quinones. Objective 3: Improve forage biomass production (quantity and quality) for increased nutrient availability and novel bio-products that integrate bioenergy production with alfalfa and other forage crops to reduce input costs while improving environmental conditions. Sub-Objective 3.1: Determine how alfalfa selected for improved stem nutritive value influences harvest management strategies and ruminant performance. Sub-Objective 3.2: Use unique harvesting practices coupled with on-farm treatment and storage to create protein-rich fractions that produce value-added products from alfalfa. Sub-Objective 3.3: Prevent excessive leaf loss during plant development and harvesting by acquiring additional knowledge of hydrolytic and regulatory factors involved in leave abscission in alfalfa, thus leading to gene-based strategies for improvement.

Approach:
We will utilize a multidisciplinary approach combining plant physiology/biochemistry, chemistry, agronomy, molecular biology and genetics. Forages provide unique nutritional and environmental opportunities to improve sustainable farming systems that help ensure food security. To enhance positive characteristics of forages, work will focus on: improving cell wall digestibility under high biomass production; and capturing more plant protein in products, e.g., milk and plant bio-products, while generating less nitrogen waste. Improved utilization of cell walls can be achieved through manipulation of genes involved in biosynthesis of structural carbohydrates and lignin. Small changes in cell wall composition may lead to decreased cross-linking and increased digestibility (Objective 1). Cell wall screening methods based on nuclear magnetic resonance spectroscopy and Fourier transformed infrared spectroscopy will be used to identify chemical characteristics related to improved energy conversion efficiency. Molecular approaches will be used to modify plant biosynthetic pathways (lignification, cell wall cross-linking, structural polysaccharides) to identify avenues for altering cell wall digestibility. Efficient capture of protein nitrogen in the rumen is related to slowing protein degradation and availability of adequate digestible carbohydrate. Molecular, chemical, and biochemical approaches will be used to determine the roles of polyphenol oxidase/o-diphenols and tannins in decreasing protein degradation during ensiling and in the rumen (Objective 2). Molecular approaches will be used to alter plants for reduced protein loss during post-harvest storage and during livestock consumption of forages. A polyphenol oxidase/o-diphenol system will be inserted into alfalfa to protect proteins during ensiling. Chemical characterization of polyphenol (e.g., o-quinones and tannins) interactions with proteins will reveal mechanisms to protect proteins from degradation and provide selection criterion for forage improvement. Multiple approaches will be used to improve forage biomass production for improve animal performance and new bio-products (Objective 3). Molecular approaches will be used to down-regulate leaf abscission genes which would prevent excessive leaf loss, preserving the protein-rich fraction of alfalfa. To improve forage biomass production for increased nutrient availability and novel bio-products, field-grown alfalfa selected for increased stem digestibility will be evaluated to reveal its potential for improved animal performance. Analysis of alfalfa leaves during plant development will determine potential changes in protein and, coupled with new harvesting techniques, will lead to improved quality, as well as new bio-products to increase utilization of alfalfa in farming systems. This project plan will increase our knowledge and understanding of current limitations associated with forage utilization and provides avenues to overcome these limitations.