Down under tactic could save farmers money on selenium


KLAMATH FALLS - By borrowing a strategy from Down Under, Pacific Northwest farmers can save money on selenium treatments for their livestock, according to researchers at Oregon State University. The strategy calls for applying selenium to pastures instead of giving selenium injections directly to cattle.

"Injections or oral treatments of selenium cost $3 to $10 per head. Applying selenium with fertilizer would cost about 33 cents a head," said Randy Dovel, a research agronomist at OSU's Klamath Falls Experiment Station.

Dovel said the selenium formulation he uses is sold commercially in Australia and New Zealand. Like the Pacific Northwest, those countries have selenium-deficient soils that produce selenium-deficient forage. Selenium deficiency causes white muscle disease of cattle and sheep, which affects the animals' reproduction, weight gain and general health.

Studies by Dovel and Ron Hathaway, Klamath County extension livestock agent, showed that about half an ounce of selenium per acre applied to the soil is enough to produce forage without deficiency. Because the amount is so small, New Zealand farmers apply a selenium salt, sodium selenite, mixed with an inert carrier.

"We found that just one pound per acre of the commercial material is all we need," Dovel said. "We mix it with a nitrogen-based fertilizer and apply it at the same time we fertilize."

Research at the Klamath Experiment Station in the 1970s and early 1980s led to wide acceptance or oral supplementation of selenium. The first time selenium fertilizer was discussed in the U.S. was at a national selenium symposium in 1995. Dovel said U.S. farmers hadn't used selenium fertilizer "because of the concern about selenium toxicity." But his studies show toxicity is not a problem at the low rates used.

Dovel tested the affects of application rates from zero to four pounds of supplementation per acre of intermediate wheatgrass. He then measured the selenium concentration in wheatgrass harvested at first cut (June 15), second cut (July 30) and third cut (Sept. 15). In all cases, the amount of selenium in the harvested plants - even at the highest application rate - was 25 times less than rates considered toxic.

"Just one pound of selenium salt per acre is enough. At that rate, there is no selenium carryover to the harvested material the next year," Dovel said. "We will run more experiments before making blanket recommendations about pasture selenium supplementation. But I'm so convinced it works, I'm using it at my place next spring."