Warm Fall Leads to Danger of Grazing Toxic-Fescue Pastures Too Short

New forage research gives reason to not graze toxic fescue grass too short. The bottom 2 inches of infected grass holds highest levels of the alkaloid causing problems for grazing livestock.

The findings guide ways to manage fescue’s toxic impact, says Craig Roberts, University of Missouri Extension forage specialist.

The message for herd owners: Don’t allow cows to grub fescue pastures into the ground.

Sarah Kenyon reports her study findings in a Ph.D. dissertation accepted at the University of Missouri this year. The results will be published in Crop Science, a scientific journal.

Kenyon, an MU Extension agronomist at West Plains, took grass samples twice per growing season for three years. The first was in April prior to boot stage (seed set) and in October prior to frost.

Previous research showed the plants are most toxic after seed set. She found that the most toxic portion is the bottom 2 inches. At seed set the plant is toxic, just not as toxic or edible.

Her findings are new, Roberts said. This will be great help in pasture grazing management.

For her study, Kenyon tested fescue owned by Tom Roberts, Alton, Mo., a cow-calf producer. The fescue is grazed and cut for hay.

In her studies, Kenyon cut fescue tillers into 2-inch segments from root crown to top. Each layer was analyzed separately by Nick Hill of Agrinostics lab in Watkinsville, Ga.

Farmers over the years developed ways to prevent poisoning. They learned that seed heads and stems were high in toxin. Grazing before seed set or clipping heads reduced toxicosis.

Now, farmers will know not to graze down to the root crown, Kenyon says. Leaving a 3-inch stubble reduces problems.

“This research can be used immediately by Missouri farmers,” Roberts said. “It will be taught at MU grazing schools.”

The toxic alkaloid, an ergovaline, is found in Kentucky 31 fescue, the most-used grass in Missouri pastures. For years, farmers knew of problems caused by toxicosis. The most serious symptom shows up in winter as fescue foot. The toxin constricts blood flow to cattle extremities. Ears, tails and feet can freeze. Tails can fall off.

The toxin comes from an endophyte fungus inside the plant. Endophyte, the scientific term, means “inside the plant.” It took years for scientists to find the tiny fungus growing between plant cells.

Fescue foot often causes lost hooves. That prevents cows from walking and grazing. Results are fatal.

Other losses can be serious but obscure. Cows abort or fail to breed. That cuts the calf crop. Calves raised on fescue gain slowly. Mama cows grazing toxic fescue give less milk.

Another symptom is brown hair that won’t shed in summer. Cattle suffering heat stress stand in ponds to cool rather than graze.

In horses, the toxin causes foal death at birth.

The best way to solve toxicosis is to kill the toxic grass and reseed a novel-endophyte fescue. Plant breeders introduced a naturally occurring nontoxic fungus into new varieties. Novel endophytes protect the plants but aren’t toxic.

Nick Hill at Agrinostics leads quality control tests for the Alliance for Grassland Renewal. The Alliance teaches farmers the danger of fescue and how to plant new novel-endophyte varieties.

In the past five years the Alliance held workshops in Missouri. It now adds other states in the fescue belt, which covers the southeastern quarter of the United States.

This year, Alliance workshops are set for March in five states: Missouri, Kentucky, Virginia, North Carolina and South Carolina.

See information on the education page of the Alliance website at www.grasslandrenewal.org.

Kenyon received her Ph.D. from the MU College of Agriculture, Food and Natural Resources, Columbia.


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