Fescue Forages

Watch out for heat stress on fescue pastures

Tall fescue dominates the transition zone between the temperate and subtropical zones of the United States and accounts for over 40 million acres of forage land. Roughly 20% of the total U.S. beef cattle herd is raised in this region. The majority of tall fescue grown is infected with an endophytic fungus. This endophyte is known to produce toxic ergot alkaloids that negatively affect cattle performance. Cattle consuming endophyte-infected fescue experience production losses exceeding $600 million per year. One of the specific negative effects is increased body temperature in cattle grazing infected fescue.



Fescue induced heat stress is believed to be caused by several factors. The ergot alkaloids are known to interfere with blood flow from the core to the peripheral tissues. Additionally, the ergot alkaloids have been shown to interfere with copper utilization in the animal, resulting in delayed shedding of winter coats.

Ergot alkaloids constrict blood flow in the peripheral tissues. This directly impedes the animal’s ability to dissipate heat through evaporative cooling. One study showed a 50% reduction in blood flow to skin over the ribs of steers fed a high-endophyte diet.

Research has also shown that ergot alkaloids interfere with copper nutrition in the animal. The ergot alkaloids make the plant less able to uptake copper from the soil and make the animal less able to absorb copper during digestion. One of the most noticeable symptoms of copper deficiency (and also fescue toxicosis) is a rough hair coat and significant delays in shedding winter coats.



Figure 1. Adaption and Use of Tall Fescue in the United States. Shaded areas represent areas of major and minor use.


This extra hair coupled with decreased peripheral blood flow results in increased body temperatures. During the heat and humidity of the summer (particularly in more southern regions), the animals’ inability to dissipate its body heat results in significant heat stress. Heat stress is very hard on cattle and results in decreased feed intake, decreased weight gain and milk production and poor breeding efficiency.

There are many management techniques that can be employed to help deal with heat stress, particularly that caused by fescue. Below are a few.

  1. Provide adequate access to cool, clean drinking water. Access to cool water is essential to help the animal cool its body temperature. Locate waterers in shady locations and keep above ground water lines shaded. Managers should check water temperature at the trough. An increase in water temperature from 70° to 95° F will more than double cattle water requirements!

  2. Provide shade. During very hot periods, make sure cattle have shade during the hottest parts of the day. Avoid using pastures that don’t provide this relief.

  3. Rotate cattle to non-fescue pastures. Research has shown that cattle body temperatures will recover somewhat within 3 to 12 days when cattle are removed from infected fescue pastures; however complete recovery from the effects of fescue toxicosis is not likely in the short term.

  4. Keep fescue seedheads clipped. If pasture rotation is not an option, manage pastures to minimize the amount of seedheads consumed by cattle. The endophyte concentrates in the seedhead and is a very potent source of ergot alkaloids. You can avoid seedheads by grazing pastures close or by regular mowing if cattle aren’t able to keep up with forage growth.

  5. Provide access to high quality mineral supplementation. The reasons for this are two-fold. First, we know that cattle have a higher water requirement during periods of heat stress, thus they will have higher urine output. Cattle will quickly lose essential electrolytes such as sodium and magnesium under these conditions. Additionally, we know that the fescue endophyte interferes with copper nutrition. Given that copper interacts with a number of other minerals in the body, the fescue endophyte ends up throwing a number of minerals off balance. Supplementation with a high quality mineral and vitamin supplement with adequate levels of potassium, magnesium, salt, copper, zinc and other trace minerals and vitamins will go a long way towards balancing out the nutritional shortfalls caused by fescue-induced heat stress.

We can nutritionally fortify our cattle to be better equipped to deal with the negative effects of heat stress caused by the fescue endophyte. One of the easiest ways to do this is with SWEETLIX® CopperHead® Fescue Max minerals. These highly palatable minerals are specially formulated for cattle on fescue forages and contain essential electrolytes in addition to a high quality trace mineral and vitamin package. SWEETLIX CopperHead Fescue Max contain a combination of organic and inorganic sources of copper, zinc, manganese and cobalt for increased bioavailability.

Figure 2. Limiting the amount of fescue seedheads consumed by cattle will help limit the levels of harmful ergot alkaloids that interfere with temperature regulation.


Heat stress is a very real concern for cattle owners utilizing fescue pastures during the summer months. You can help cattle regulate their body temperature by providing cool water and shade. You can also limit the amount of ergot alkaloids ingested by limiting grazing of fescue seedheads. Finally, you can nutritionally fortify cattle to better handle heat stress. One such nutritional option is SWEETLIX CopperHead Fescue Max minerals.

Ask for SWEETLIX by name at your local SWEETLIX dealer or call 1-87-SWEETLIX to speak with a SWEETLIX nutritionist for more information.

CopperHead® is a registered trademark of Ridley Block Operations