Walking through a pasture, feeling the grass and catching the scent of cattle nearby, everything may seem normal. But when noticeable changes appear in the herd, producers’ concerns may start to grow.

Since 1931, when University of Kentucky professor E.N. Fergus discovered tall fescue grass, researchers and producers have worked together to fight a common issue: fescue toxicosis in tall fescue grass or “Kentucky 31.”

Tall fescue can be traced back to one hillside in Menifee County, Ky., on a farm owned by William Suiter. Tall fescue used to be called Suiter’s grass, because he had the only green grass around.” — Michael Trammell, Oklahoma State University (OSU) agronomy extension specialist

He says tall fescue is a bunch grass grown as a cool-season perennial by producers, noting the plant is hardy and able to withstand considerable heat and drought stress.

Shortly after tall fescue was discovered, researchers found toxicity growing within the plant. Between 1931 to 1943, almost $60 million of beef production losses came from Kentucky 31.

“Researchers found some pastures with Kentucky 31 were infected with the fungal endophyte, neotyphodium coenophialum,” Trammell says, “which produces ergot alkaloid chemicals, further infecting the plant.”

The fungal endophyte lives between the cell walls of tall fescue. The fescue will go to reproductive stage, and the endophyte will travel through the stem and colonize into the seed head. The seed drops and growth starts over again.

“The fungal endophyte is transmitted from generation to generation through the seed,” Trammell explains. “Endophytes don’t jump from plant to plant out in the field. The toxicity is all transmitted in the seed.”

When tall fescue is infected and contains the endophyte and ergot alkaloids, the plant can become more vigorous, pest-resistant, drought-resistant and tolerant to adverse soil conditions, he explains.

The fungus is what gives tall fescue the ability to be drought tolerant and persistent. We try to find better varieties for producers and for beef.” — Ronald Trotta, University of Kentucky animal and food sciences assistant professor and fescue toxicosis researcher

Researchers have discovered different varieties and solutions to provide for producers, Trotta adds. New versions include endophyte-free tall fescue, which replaces the fungus but keeps the hardiness of the plant, and novel endophyte tall fescue, which does not produce toxic alkaloids.

Trotta says one problem researchers have is growing new varieties of tall fescue each year and convincing producers to use newly developed or different varieties.

“If you were to tell a farmer to burn their whole pasture to replant and use novel endophyte-free tall fescue varieties, it is too much work,” he says. “It is too much money. The seed costs $5 per pound (lb.) compared to $2/lb. for Kentucky 31 tall fescue.”

If the price is not the issue, the hardiness may be for some producers. The endophyte-free tall fescue varieties are not as drought-tolerant as Kentucky 31, and producers are forced to reseed the new variety, Trotta says.

Either way, some producers are not even aware their pastures have infected tall fescue.

“You can’t physically see infected tall fescue,” Trammell explains. “Producers buy kits to test if pastures are infected. Not every pasture is 100% infected with an endophyte.”

Many cattle accidentally consume fescue toxicosis if producers are unaware of infected pastures, Trammell says, which can lead to health issues and income loss for producers.

Physical indicators cattle have consumed fescue toxicosis include fescue foot, which is loss of the hoof, loss of switch on tails, loss of tips of ears and unregulated body temperatures.

“One of the symptoms we see is cattle do not shed their haircoat,” he adds. “Animals will stand around in water or mud trying to cool off during the summer because they are on summer fescue and did not shed their winter coats.”

Until producers see the physical indicators, the cattle will continue to decrease in weight and can lose up to 1.5 lb. a day if the cattle are grazing infected tall fescue.

Along with the physical indication of cattle grazing infected tall fescue, some internal indicators include heat intolerance, lack of blood flow and low conception rates.

“The ergot alkaloids in fescue bind to specific receptors in blood vessels, causing vasoconstriction,” Trotta says. “This reduces blood flow to critical areas like the gut, decreasing nutrient absorption and activating the immune system.”

In 2024, he received a $300,000 USDA grant to study 5-hydroxutytophan in mitigating fescue toxicosis in beef cattle. Since his study has started, Trotta has found serotonin helps symptoms in cattle that have ingested the toxicity.

Increased serotonin bioavailability is expected to relax blood vessels, improve dry matter intake and reduce immune system activation, which Trotta says will counteract the effects of ergot alkaloids.

“To give more 5-hydroxutytophan, we are increasing the serotonin levels in cattle,” he explains. “The idea being we’ll eventually demonstrate increasing serotonin in cattle causes relaxation in blood vessels and therefore mitigates the vasoconstriction caused by ergot alkaloids.”

Cattle can dissipate heat better and eat better after replacing one of the major symptoms of fescue toxicosis, which is vasoconstriction. If the first problem is fixed, the second problem with dry matter intake can be fixed and growth can increase, he adds.

If producers have tested pastures and have fescue toxicosis, many strategies can be used to manage or dilute the plant, says Lisa Baxter, University of Georgia crop and soil sciences assistant professor and state forage specialist.

“We work a lot with producers on the dilution effect,” Baxter says. “Feeding nontoxic hay, growing white clover in fescue areas or doing seedhead suppression chemically are always good ways to help reduce the amount of fescue toxicosis in pastures.”

Using these practices slows fescue toxicosis growth down, Baxter says. With the increasing temperatures in Georgia and working with producers, fescue toxicosis has slowly disappeared within pastures in the state.

“For long-term decisions, switching to novel endophyte tall fescue or the endophyte-free tall fescue varieties is the best solution for producers,” she adds.

Other ways to manage the plant include mowing seed heads in the infected pasture, using herbicides, rotationally grazing and using feed supplements.

The goal is to help producers manage fescue toxicosis, Trotta says, and while doing that, keep finding solutions to the side effects cattle experience after ingesting the plant.

“Nine million beef cattle in the U.S. are subjected to fescue toxicosis every year by at least 50 lb.,” he says. “Since 2015 $2 billion every year is lost. Of this $2 billion, $1.5 billion is thought to be from reproductive loss.”

Today, fescue toxicosis has affected 13 states from the eastern U.S. to the Central Plains, and of these 13 states, 86 million acres of Kentucky 31 have been found.

“The goal is to find something that physiologically allows the animal to return to normal homeostasis,” Trotta says. “Producers want something they can feed, manage easily and is economically feasible to incorporate into a program.”