Transgenic Alfalfa Yields New
Agricultural engineer Richard Koegel expresses juice from transgenic alfalfa
containing the enzyme phytase and xanthophyll, as well as proteins suitable for
Imagine a world of well-fed pigs and poultry without the environmental
hazard posed by their waste.
Such a thought is bringing a smile to Agricultural Research Service and
University of Wisconsin researchers. They've joined forces to solve the
pressing animal waste disposal problem by developing a special type of alfalfa
and a way to harvest its valuable enzymes.
ARS agricultural engineer Richard G. Koegel, who is at the U.S. Dairy Forage
Research Center in Madison, Wisconsin, has designed processes to separate three
important components from alfalfa.
But this isn't ordinary alfalfa. It's genetically altered alfalfa the
university researchers created that yields industrially valuable enzymes not
normally found in alfalfa.
Phytase is one of these components. Hog and poultry producers know the value
of phytase, because it can reduce the need for costly phosphorus supplements in
rations. Phytase frees grain-bound phosphorus so it can be used by nonruminants
such as chickens and pigs.
Improving phosphorus utilization in these animals can decrease its excretion
in their manure. Each year in the United States, hogs and poultry excrete about
30 million tons of manure containing 460,000 tons of phosphorus.
Phytase made by fermentation has been shown to increase animals' phosphorus
uptake by up to 42 percent. Phytase extracted from the transgenic alfalfa is
expected to be cheaper than either traditional supplements or phytase made by
Feed is the most costly part of raising hogs and poultry, and phosphorus
supplements cost about $3 per ton of feed. Alfalfa-produced phytase may cost
only half this much. [For more on phytase, see
Corn Has Low Phytic Acid," Agricultural Research, December
1996, pp. 12-14.]
In addition to phytase, the transgenic alfalfa yields proteins and
xanthophylla pigmenting substance used by the poultry industry to give
yellow color to egg yolks and poultry skin.
"The equipment used to extract alfalfa juice isn't terribly
complicated. But it's critical to produce a uniform, concentrated product
suitable for storage and shipping," says Koegel.
"We beat the fresh alfalfa in a mill with high-speed rotating hammers
to rupture the cell walls and then pass it through a continuous press, which
expresses juice. Farmer cooperatives and commercial livestock-producing
companies are likely to own this equipment."
Although the equipment Koegel is now using is stationary, he says similar
equipment could be designed for field use.
"We are challenged, though, to produce a stable, concentrated product.
Xanthophyll oxidizes and quickly deteriorates if not processed and stored
properly. We're working on methods to extract and concentrate phytase and
xanthophyll at lower cost and with a less energy consumption," says
The alfalfa juice also provides new sources of human dietary protein. Koegel
and others previously designed an extraction system that is now used by several
villages in northern Mexico to enhance the largely grain-based,
protein-deficient diets there.By Linda Cooke
McGraw,Agricultural Research Service Information Staff, 1815 North
University Street, Peoria, IL 61604, phone (309) 681-6530.
Richard G. Koegel is at the
USDA-ARS Dairy Forage Research Center,
1926 Linden Dr. West, Madison, WI 53706; phone (608) 264-5149, fax (608)
"Transgenic Alfalfa Yields New Products" was published in
the April 1998 issue of Agricultural Research magazine. Click here
to see this issue's table of contents.