Project Number: 5090-21000-071-000-D
Project Type: In-House Appropriated
Start Date: Mar 25, 2019
End Date: Dec 10, 2023
Objective 1: Develop or adapt poly-phenol systems in forage legumes for improved N use efficiency in dairy production systems. Subobjective 1.1: Evaluate efficacy of the polyphenol oxidase (PPO)/o-diphenol system on preserving true protein during ensiling and improving N-use efficiency. Subobjective 1.2: Determine the chemical basis for proteolytic inhibition caused by PPO-generated o-quinones. Subobjective 1.3: Develop strategies to produce optimal levels of PPO substrates in alfalfa. Objective 2: Develop or adapt tannin systems in forage legumes for improved N use efficiency in dairy production systems. Subobjective 2.1: Determine the chemical basis for protection of protein during rumen digestion and providing elevated levels of escape protein into the hindgut by condensed tannins (CTs). Subobjective 2.2: Analyze the effects of harvesting and storage methods on active CT content and protein preservation. Objective 3: Improve forage digestibility and nutrient utilization efficiency in the cow through physiological modifications. Subobjective 3.1: Prevent excessive leaf loss during plant development and harvesting by identifying genetic factors involved in leaf abscission in alfalfa providing a foundation for gene-based strategies for improvement. Subobjective 3.2: Use genetic manipulation of sugar nucleotide biosynthetic pathways to identify avenues for altering cell wall structural polysaccharides and matrix interactions. Subobjective 3.3: Explore alfalfa physiological mechanisms to enhance the utility of alfalfa as a cattle feed and other uses. Objective 4: Improve forage silage quality and preservation to lessen forage losses, improve nutrition value for the cow, enhance soil ecology, and reduce environmental impacts for integrated dairy systems. Subobjective 4.1: Incorporate non-traditional silage additives (novel forages, inoculants, concentrates) and management strategies to reduce forage loss and improve relative nutrition in the animal. Subobjective 4.2: Leverage computational and sequencing technologies to elucidate connections between plant, silo, and animal microbiomes. Objective 5: Develop system-based models to assess the productivity, efficiency, and environmental impact of dairy forage production. Develop a whole-farm dairy simulation model that can be used to assess the impact of forage crop modifications and management on farm-scale nutrient cycling, farm crop and milk productivity, and environmental impacts.
Will utilize a multidisciplinary approach combining plant physiology/biochemistry, chemistry, agronomy, microbiology, molecular biology and genetics, and computer modeling. 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 capturing more plant protein in products, i.e., milk and plant bio-products, while generating less nitrogen waste; improving the amount of digestible cell wall biomass; and developing approaches to best maintain and optimize nutritional quality after harvest and during storage. We will also evaluate impacts of forage improvements and management by whole farm modeling. 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 (Objectives 1 and 2). Molecular approaches will be used to introduce a polyphenol oxidase/o-diphenol system into alfalfa to protect proteins during ensiling, including optimizing biochemical pathways in alfalfa to produce the o-diphenol PPO substrates. 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 production of digestible forage biomass (especially carbohydrate) for improved animal performance (Objective 3). Molecular approaches will be used to down-regulate leaf abscission genes which would prevent excessive leaf loss, preserving a highly digestible fraction of alfalfa. The role of sugar nucleotide biosynthetic pathways in cell wall assembly and their influence on digestibility will be evaluated using molecular biology and biochemistry techniques. Approaches to maintain and optimize nutrition of preserved forages will be investigated using engineering, microbiological, and genomic approaches (Objective 4). Novel silage additives to prevent nutrient losses (for example via volatile organic compounds) will be investigated at lab and farm scales; microbial selection will be used to improve silage fermentation profiles, which could have impacts on greenhouse gas emissions; and metagenomics will be used to examine the complex interactions of field, silo, and rumen microbiomes. In order to better assess how changes in forages and forage management/storage impact the whole farm/agroecosystem, better whole-farm computer models will be developed with collaborators inside and outside of ARS (Objective 5). This project plan will increase our knowledge and understanding of current limitations associated with forage utilization and provides avenues to overcome these limitations.