May 15, 2004
May 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 scientists with the U.S. Department of Agriculture's Agricultural Research Service (ARS).
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 humans.
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 USDA's chief scientific research agency.