Even though it's known as the queen of forages, alfalfa needs some retooling.
“It's getting harder for alfalfa to compete with the large and consistent supply of good-quality corn silage,” says Neal Martin, director of the U.S. Dairy Forage Research Center (USDFRC), Madison, WI. “So our scientists are working on ways to enhance it.”
Researchers estimate that forage producers will have access to redesigned alfalfa within five to 10 years. Using biotechnology and traditional breeding methods, they're working to improve the crop's fiber digestibility, protein utilization and yield.
Here's a synopsis of their progress:
“The fastest and best way to get the biggest gains in fiber digestibility is by either developing plants with less lignin or plants with a different type of lignin,” says Martin.
To achieve that goal, scientists from the USDFRC and the USDA-ARS Plant Science Unit in St. Paul, MN, are collaborating with researchers from the Samuel Roberts Noble Foundation in Ardmore, OK, and Forage Genetics International, West Salem, WI. They've recently been successful at “down regulating” a gene so less lignin is produced, thereby improving digestibility.
The USDFRC estimates that a 10% increase in alfalfa fiber digestibility would lead to a $350-million increase in U.S. milk and beef production annually, and a 2.8-million-ton annual decrease in manure solids.
Reducing protein degradation during ensiling is another priority, says Martin.
“In order to do that, we're researching ways to make alfalfa act more like red clover during ensiling,” he says.
When alfalfa's ensiled, protein degradation can reach 80-90%, compared with only about 20% for red clover, according to Martin.
Red clover's reduced protein degradation is due to enzymes called polyphenol oxidases (PPOs), which react with substrates to produce reactive molecules called quinones. The PPO-generated quinones combine with plant proteins to reduce protein breakdown.
The researchers are taking PPO-producing genes out of red clover and inserting them into alfalfa.
The next step is to find a mechanism for alfalfa to produce a suitable substrate or to add a substrate with similar activity. Chlorogenic acid, abundant in potato skins and coffee grounds, has been shown to work. So has caffeic acid. When alfalfa with a PPO gene has caffeic acid added during ensiling, it behaves like red clover, with less protein degradation.
The Noble Foundation is also spearheading research to engineer alfalfa to produce condensed tannins in leaves and stems. Condensed tannins bind with plant proteins to slow the rate of protein degradation in the rumen, increasing bypass protein. Tannin-containing forages are also non-bloating.
Scientists at several locations are working to improve alfalfa's yield potential. It's needed, says Mike Velde of Dairyland Seeds, Clinton, WI.
“As herd sizes continue to grow, the ability of dairy producers to harvest enough alfalfa becomes more difficult,” says Velde. “Instead of 5 tons/acre, producers need to be getting 7-8 tons/acre on a consistent basis.”
His company's approach is to develop hybrids with yield-enhancing heterosis.
“We're in the process of identifying high-yielding individual plants,” says Velde. “Once we have the best plants, we cross them in different combinations to identify specific crosses that produce the greatest yields.”
Yield increases are likely to be gradual, he adds.