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United States Department of Agriculture

Agricultural Research Service

Research Project: REDESIGNING FORAGE GERMPLASM AND PRODUCTION SYSTEMS FOR EFFICIENCY, PROFIT, AND SUSTAINABILITY OF DAIRY FARMS Title: Progress report on reduced-lignin alfalfa: part 1, plant modifications

Authors
item Riday, Heathcliffe
item Hatfield, Ronald

Research conducted cooperatively with:
item Forage Genetics International

Submitted to: Forage Focus
Publication Type: Trade Journal
Publication Acceptance Date: August 1, 2009
Publication Date: August 1, 2009
Citation: Riday, H., Hatfield, R.D. 2009. Progress report on reduced-lignin alfalfa: part 1, plant modifications. Forage Focus. May. p. 2-3.

Interpretive Summary: Alfalfa is the most important forage legume in U.S. dairy cow diets because it has a high protein content, it increases feed intake and milk production, and it is an excellent complement to non-forage components of dairy cow diets. But the cell wall lignin in alfalfa (as with other plants) cannot be digested by dairy cattle. Researchers have been studying lignin for many years in an attempt to find ways for cows to more completely digest cell walls. Using reduced-lignin transgenic alfalfa plants produced by Forage Genetics International and the Samuel Roberts Noble Foundation, researchers at the U.S. Dairy Forage Research Center, in collaboration with the Consortium for Alfalfa Improvement, conducted a study to evaluate two key lignin biosynthetic enzymes (referred to as COMT and CCOMT) in alfalfa plants to determine the agronomic effects of downregulating these enzymes in a field setting. Early studies show that agronomically useful lignin-modified cultivars are commercially feasible because, wherever the plants are grown, the reduced lignin trait will be expressed without negatively impacting alfalfa stand performance. This study provides important information to plant breeders as they move forward in developing reduced-lignin alfalfa plants that may improve the efficiency of alfalfa digestion by dairy cattle.

Technical Abstract: Alfalfa is the most important forage legume in U.S. dairy cow diets because it has a high protein content, it increases feed intake and milk production, and it is an excellent complement to non-forage components of dairy cow diets. It is also an excellent source of effective fiber which is essential for maintaining proper rumen function and cow health. With alfalfa, as with other plants, contents inside the cell wall (i.e. protein, soluble sugars, and starch) are completely digestible. Sometimes, however, intact cell walls keep cell contents from being “released” during digestion, making these nutrients unavailable to the cow. Alfalfa would be a better energy source if more carbohydrates within cells were available. Using transgenic alfalfa plants produced by Forage Genetics International and the Samuel Roberts Noble Foundation, researchers at the U.S. Dairy Forage Research Center, in collaboration with the Consortium for Alfalfa Improvement, conducted a study to evaluate two key lignin biosynthetic enzymes (referred to as COMT and CCOMT) in alfalfa plants to determine the agronomic effects of downregulating these enzymes in a field setting. Plants were grown in three field environments (Prairie du Sac, WI; West Salem, WI; and Ardmore, OK) and harvested three to four times a year at each location during 2005 and 2006. Transgenic alfalfa plants have been generated that show decreased lignin content and increased fiber digestibility. Early studies show that agronomically useful lignin-modified cultivars are commercially feasible because, wherever the plants are grown, the reduced lignin trait will be expressed without negatively impacting alfalfa stand performance. Future research will focus on additional or alternative ways to decrease lignin’s impact on digestibility, such as understanding how lignin cross-links to other wall components.

Last Modified: 7/23/2014
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