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Tall fescues need endophyte fungus, but not toxins that poison beef herds

The strongest cool-season grass pastures come from varieties of tall fescue infected with a fungus. This infection can be good — or bad.

Duane Dailey 1

January 27, 2017

3 Min Read

It took decades to discover tall fescue internal fungi are not created equal. Fungus that grows between cell walls in tall fescue plants are difficult to see even with high-power microscopes.

Plant scientists now know, and all grassland farmers should know, that the fungus in Kentucky-31 variety tall fescue is a bad one, the worst.

Losses from bad endophyte, which is found in most fescue pastures across the southeastern United States, cost $600 million a year to the beef industry alone.

Sarah Kenyon, University of Missouri Extension regional agronomist, West Plains, gave the lowdown on the difference. Speaking at the annual MU Crop Conference, she outlined the downside of toxic tall fescue.

First the good news: The fungus, called an endophyte because it grows inside the plant, is essential for fescue survival.

The bad news is that the endophyte found in K-31 fescue produces an alkaloid. That toxin costs Missouri beef producers $180 million in lost production. That’s every year.

Kenyon listed causes of losses in cow herds: lower conception rates, reduced milk production, reduced feed intake, rough hair coat, increased core body temperatures in summer and lower blood circulation in winter. The latter allows frozen noses, ears and tails.

The first and most noticeable loss seen was what became known as “fescue foot.” That’s when feet freeze and hooves fall off, leaving bloody stumps. Animals that can't walk must almost always be put down.

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Fescue foot is very visible. Unfortunately, more widespread and less noticed are other losses, especially low conceptions and gains, says Craig Roberts, MU Extension forage specialist. Those are often not seen when they occur.

Roberts is active in the Alliance for Grassland Renewal, which has worked across Missouri and now nationally in spreading the word on toxic fescue replacement.


For four years, the Alliance held schools in Missouri.

Now, they share news with producers in other states that have toxic fescue. Schools will be added in Kansas and Kentucky.

Extension services with Kansas State University and University of Kentucky aid the program.

2017 school dates and locations:

  • March 6, Mound Valley, Kan., at the Community Center.

  • March 7, Mount Vernon, Mo., at the MU Southwest Research Center.

  • March 9, Lexington, Ky., at the UK Veterinary Diagnostic Lab.

  • Each school runs 9 a.m. to 5 p.m.

  • The schools teach how to solve toxin problems.

Endophyte fescue found in the wild can be bred into new fescue varieties. Those endophytes provide plant protection but not toxic alkaloids.

Plant breeders call these beneficial fungi “novel endophytes.” Early on, plant breeders removed the toxic endophyte. Those non-endophyte varieties didn’t survive.

Endophytes, among other things, provide protection to the grass from drought, diseases, insects and overgrazing.

Novel-endophyte fescues give protection. However, they cannot be mismanaged like the toxic varieties.

Grazing cattle find the novel-endophyte fescue tastier. Cattle continue grazing past time that they would be driven away by the alkaloids.

The toxins create heat stress, sending cattle to the shade or into ponds to cool down. Now, farmers must manage pastures with rotational grazing. There are other benefits from controlled grazing.

Advance registration for limited seating is required. Registration details are at http://grasslandrenewal.org.

Instructors include Extension specialists, seed industry leaders and farmers.

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