If your pastures are in the “fescue zone” — the central U.S. from southern Iowa down through Arkansas, and from the mid-Atlantic states west to Kansas — your fescue likely has a toxicity problem. Most growers just can't see the impact it has on their animals, says University of Missouri state forage specialist Craig Roberts.

“Actually, there's only a 5-10% chance your fescue pastures don't have a toxicity problem, so I tell growers, ‘You need to manage for it’,” he says.

Nearly all tall fescue pastures planted before 1980 are infected with a microscopic fungus commonly known as the endophyte. It grows inside the plant, producing compounds, commonly alkaloids, that can sicken animals that graze the grass. These toxins cost livestock producers an estimated $900 million in production losses annually.

Roberts is on a crusade of sorts to better educate livestock producers about the impact of tall fescue toxicosis through workshops and field demonstrations.

“The best way to convince them that there is a problem in their pastures is to show them the difference between cows grazing infected and non-infected pastures,” he says. “When they have them side by side, it's easier to pick up on small things, like rougher hair coat or how far down the cattle graze the field.”

Beyond the most obvious physical sign of toxicosis — fescue foot or hoof loss due to lack of blood flow to the foot — there are many less visible symptoms, including narrowed blood vessels, high body temperature, increased respiration, low heart rate and suppressed immune system. All of these changes lead to less milk production, reduced forage intake, low rate of gain and reproductive problems.

“Before you look at possible solutions, you need to determine how infected your pastures are,” says Roberts.

That requires getting an endophyte test, which will tell you what percentage of your field is infected. April is the earliest that pasture samples can be taken, he notes, since the crop is rapidly growing and alkaloid levels usually start to build then. Many university labs conduct these tests, so contact the one nearest you for details.

“Infection levels of 30-35% are considered moderately infected, and a producer should think about eradicating the toxic tall fescue and replanting the pasture to another grass or an endophyte-free tall fescue cultivar,” he says. “The biggest weakness of the endophyte-free tall fescues is that they may not persist as well as other tall fescues.”

Newer varieties that contain a novel, or beneficial, endophyte are non-toxic and produce good forage. One of those varieties, with the MaxQ endophyte, is available now, and more are expected on the market in two years, he notes.

“In the meantime, growers who can't justify totally replanting their pastures have some other options,” says Roberts.

Moving animals to non-toxic summer grazing, such as to alfalfa or bermudagrass, is one way to reduce the amount of toxins they ingest, says Roberts.

“Tall fescue is fairly toxic by late May. When seed heads start to emerge, the toxicity level goes up because there is a higher concentration of the fungus in the seeds.”

By interseeding a legume such as white clover in the tall fescue pasture, you can measurably dilute the toxins and improve animal gain.

“If you're losing a pound of gain due to grazing toxic fescue, you could recapture 25-40% of that pound by interseeding a clover into that pasture,” he says.

Providing supplemental feeds is another good way to dilute the toxins, says Roberts. “Corn gluten and soybean hulls are good byproduct options.”

Other steps for reducing alkaloid levels include: Apply less nitrogen fertilizer on tall fescue pastures, ammoniate tall fescue hay and save stockpiled tall fescue hay for late-winter feeding.

“When pastured animals aren't performing well, I often hear producers say, ‘That's just the way cattle look this time of year.’ The University of Missouri workshops help show them it could very well be a problem in the pasture, and that's something they can better manage,” says Roberts.