Fescue Toxicity in Cattle: How It Can Be Managed

If a grass could ever be described as a double-edged sword, it would be tall fescue.


Brought to the United States from England in the late 1800s, tall fescue is incredibly hearty and drought resistant and grows well in a wide array of temperatures. Fescue grass is a cool-season grass that provides large quantities of forage year-round in many places and stays green into the winter months in some areas. However, this grass is often low quality and can be deadly to cattle.


Where are Tall Fescue Grasses Located?

The University of North Carolina and the University of Missouri report that more than 40 million acres of tall fescue exist in the United States today. The dominant variety of tall fescue, called Kentucky-31, runs from the Eastern United States to Oklahoma. Also called the “fescue belt” this area contains roughly 25% of U.S. beef cattle.


What is Fescue Toxicity in Cattle?

K-31 fescue contains a fungal endophyte, Neotyphodium coenophialum, which in part gives the grass its durable traits. However, the fungal endophyte also produces ergot-alkaloid compounds that are toxic to cattle.


Symptoms of fescue toxicity in cattle:

  • Decreased feed intake and lower weight gains

  • Rough hair coats

  • Short tails

  • Slow loss of winter hair in the spring

  • Slow breed back

  • Severe lameness

  • Fescue foot where in some cases hooves fall off

  • Low tolerance for heat stress

The reason this toxin causes so much damage in cattle is that it is a vasoconstrictor, meaning it constricts blood flow.


Effect of Fescue Toxicity on Cattle

When fescue toxicity constricts blood flow in cattle, it impacts the entire body. Think of it this way: it works similar to diabetes in humans who have poor blood circulation and feet issues. When toxic fescue limits blood flow, hair and hooves are restricted in nutrients, causing rough coats, short tails and lameness.


Additionally, this increases the risk of heat stress since animals cannot dissipate heat through the bloodstream. Even with good blood flow, cattle struggle to dissipate heat effectively. Cattle sweat at about 10% the rate of humans. Under heat stress, cattle will begin to pant, drool and push blood to their extremities to cool themselves. However, if cattle have fescue poisoning, they cannot effectively push blood to the surface of their bodies to get rid of heat.


Humans actually do the same thing. When you run, your face gets red because you are pushing blood to the surface of your skin to cool down.


Cow showing symptoms of fescue toxicity with a rough hair coat.

Animals are also more likely to experience disease and infection, as fescue toxicity weakens their immune systems.


Interestingly enough, cows can actually detox themselves from fescue to varying degrees. However, this detoxifying process results in significant oxidative stress, creating its own set of issues that need be addressed.


Oxidative stress is caused by the imbalance of excess free radicals in the body. Free radicals are naturally occurring and are utilized by the immune system to fight disease as well as normal metabolic function. But, during times of stress (environmental, nutritional or, in this case, fescue toxicity), too many free radicals are produced, and they begin harming sensitive tissue and molecules that are necessary for optimal performance in cattle.


How to Manage Fescue Toxicity in Cattle

There are three primary ways to help cattle manage fescue toxicity.

1. Dilute the fescue with warm-season grasses or have fescue free pastures that can be utilized during the summertime.

To lower the levels of toxins and tall fescue in one location, it is important to start seeding pastures with a variety of grasses. This will help dilute the level of toxins cattle ingest. It is suggested to plant legumes, such as clovers and alfalfa. Legumes are warm-season grasses that can help dilute pastures while adding nitrogen back into the soil.


2. Do NOT let fescue grass go to seed.

The most poisonous part of fescue grass is the seed head. It is recommended to graze these fields hard to prevent grass from going to seed. Otherwise, mow it regularly. If you plan to bale fescue, do so before it goes to seed. Otherwise, you will continue to see fescue toxicity into the winter.


3.Antioxidants, essentials oils and trace minerals can help

Antioxidants are proven to help lower oxidative stress. As stated above, oxidative stress causes an imbalance of free radicals. Free radicals are atoms that have an uneven number of electrons. They are on the hunt for an additional electron to balance the atom, and they will steal an electron wherever they can find one, including from cells that promote immune function and tissue growth.



Antioxidants are molecules capable of slowing or preventing the oxidation of other molecules because they can share electrons and reduce free radicals. There are many antioxidant options today -- including natural vitamin E, trace minerals and essential oils. However, the effectiveness of available options varies significantly.


Oxygen radical absorbance capacity (ORAC) is a method used to determine the antioxidant capacity of a given compound. Vitamin E has an ORAC score of 48,200 while Ralco’s essential oils have an ORAC score of 2,349,200 - 40 times greater than vitamin E. Additionally, research shows us essential oils are vasodilators and can help increase blood flow and heat dissipation in cattle under heat stress.


Trace minerals also have antioxidant properties to help lower oxidative stress and support challenges in reproduction and immunity that are amplified with fescue toxicity.


See What Ralco’s Cattle Line Up Can Do for Your Operation

Ralco's proven Summit™ Mineral line-up provides balanced and highly available trace minerals and an essential oil additive called Comfort™ that can be included to help manage oxidative stress, heat stress and fescue toxicity.


To learn more, contact Ralco’s ruminant nutritionist Dr. Jeff Hill by calling 507-337-6916 or emailing RuminantHelp@RalcoAgriculture.com.