Help Control Leafy Spurge
January 21, 2004
Certain sheep that have a healthy
appetite for leafy spurge may help control this aggressive perennial that has
infested more than 5 million acres of U.S. rangeland, according to
Agricultural Research Service
ARS animal geneticist Brent W. Woodward and rangeland scientist Steven S.
Seefeldt, at the agency's U.S. Sheep Experiment Station in Dubois, Idaho, have
teamed together to determine why some sheep seem to have a strong preference
for leafy spurge. Is this taste for the plant--with its sticky, milky sap--in
the animals' genes, or is the dietary inclination something that individual
sheep learn through observation?
It's an important question to answer, because leafy spurge's spread across
western rangelands has greatly reduced plant diversity and productivity.
While cattle and horses generally avoid leafy spurge, some sheep will graze
on it. Hoping to take advantage of this tendency, the ARS scientists have
recently initiated studies to investigate those sheep's apparent appetite for
leafy spurge and other plants with similar chemical profiles.
Finding a genetic component to sheep's preference for leafy spurge wouldn't
be surprising, according to Woodward, since scientists are already finding that
a genetic code is responsible for taste sensitivities in mammals, including
The researchers' ultimate goal is to selectively breed sheep that will pass
along, from generation to generation, an inclination to eat leafy spurge.
Seefeldt envisions employing spurge-loving sheep as biological control
agents to graze on patches of the invasive plant.
Based on initial visual measurements--including the challenging task of
conducting sheep bite counts--the scientists found that there are two different
kinds of eaters. Some sheep consume leafy spurge readily, while others eat it
only if forced, over time, because of lack of other forage.
ARS is the chief scientific research agency of the
U.S. Department of Agriculture.