A row of wilted, chopped, green alfalfa is collected into a wagon before being taken to the silo.  Click the image for additional information about it.

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Helping Stored Alfalfa Keep Its Protein

Cows will soon have a better chance of getting their needed protein. Scientists with the Agricultural Research Service recently discovered an environmentally friendly way to reduce the protein breakdown that occurs when forage crops like alfalfa are processed into silage, the winter feed of many livestock.

Because it's high in protein, alfalfa is an ideal crop for livestock. Unfortunately, when it's processed by storing and fermenting its clippings in silos, up to 85 percent of alfalfa's protein breaks down into nonprotein nitrogen, which can't be used as efficiently by the cows' bodies.

ARS plant physiologist Ronald Hatfield, agricultural engineer Richard Muck and molecular biologist Michael Sullivan have found an answer to the problematic breakdown of protein in--of all things--red clover and potato skins. The scientists work at ARS' U.S. Dairy Forage Research Center in Madison, Wis.

Red clover contains large amounts of an enzyme called polyphenol oxidase, or PPO. When red clover is chopped up, its cells release the PPO. When the PPO is exposed to oxygen, it reacts with caffeic acid naturally present in the clover and forms o-quinone molecules. These molecules bind to the enzymes that cause the breakdown of red clover's protein, thereby keeping more protein intact.

Alfalfa has significantly lower levels of PPO. So to take advantage of this PPO-caffeic acid combination to protect alfalfa's protein, Sullivan and ARS plant pathologist Deborah Samac "borrowed" the PPO gene from red clover and inserted it in alfalfa plants. When the altered alfalfa plants were chopped and treated with caffeic acid, they had 15 percent less protein degradation after two weeks than did untreated alfalfa plants.

Caffeic acid is present in high concentrations in a variety of fruits and vegetables, most notably potato skins, a common agricultural waste product. The scientists are working with different potato processing plants to see how easy it would be to extract large amounts of caffeic acid from leftover skins.

Read more about the research in the December issue of Agricultural Research magazine.

ARS is the USDA's chief scientific research agency.