Farm Progress

The results of a University of Missouri study find liming a pasture does not increase ergovaline.

Duane Dailey, Freelance

February 23, 2017

2 Min Read
LIME HELPS: Spreading lime boosts spring pasture growth. Now, University of Missouri researchers have found it does not boost the toxicity found in many of the state's fescue pastures, which can cause production problems for cattle.fotokostic/iStock/Thinkstock

Adding poultry litter or nitrogen to toxic fescue pastures grows more grass, but also boosts toxins in the grass. However, a three-year study at the University of Missouri shows liming helps grass but doesn't increase ergovaline.

Ergovaline is a toxin that harms grazing cattle in many ways — mostly in lost production. In recent frigid cold, farmers reported cases of fescue foot caused by the toxin. Cattle losing their hooves must be put down.

"Before the study, we didn't know the impact of lime on toxin in infected fescue," says Sarah Kenyon, an MU Extension agronomist in West Plains.

The study
Kenyon completed her graduate degree with a study on a farmer's pasture in her area. The site was a 20-year-old stand of pure fescue with a 98% infection rate. It was "hot" with toxin. Kenyon replicated her tests on 22 plots over three years.

No one had studied lime impact on fescue toxicosis, a major problem for grazing herds. The toxin is estimated to cause $900 million in losses annually in U.S. cow herds.

"A major finding of her [Kenyon's] work is that liming causes no harm. We didn't know that," says Craig Roberts, MU Extension forage specialist. "We did know that nitrogen fertilizer fed the fungus living in the grass."

It was long-known that adding lime is the first step to improve pasture fertility. Calcium boosts pH, which cuts soil acidity. This allows fertility to be released for grass roots.

Impacts of nitrogen
"Nitrogen fertilizer boosts forage yields, as farmers have long known" says Rob Kallenbach, MU Extension agronomist. But there is a flip side, he says. "Nitrogen fertilizer also feeds the fungus, which in turn creates more toxins."

A common control of fescue toxicosis is to withhold nitrogen. That drops yields, which cuts gains on grazing livestock. That loss is on top of loss from fescue toxicosis.

Problems with toxic fescue can be solved by killing the old fescue and reseeding a new variety of novel-endophyte fescue.

Fescue must have an endophyte to survive insects, diseases, drought and overgrazing. The most widely grown grass across the Southeastern United States is Kentucky 31 fescue. It happens to contain the toxic endophyte. Other endophytes found in nature do not make toxin.

Seed producers now use nontoxic novel endophytes. Many of these new fescues are sold by several companies.

Dailey is a retired MU Extension professor. He writes from his home in Columbia.


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