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 percent of all beef cattle herds in the U.S. are raised in this region. Unfortunately, most tall fescue is infected with an endophytic fungus known to produce toxic ergot alkaloids, which negatively affect cattle performance. Cattle consuming endophyte-infected fescue experience production losses that exceed $600 million per year.


One of the specific negative effects of grazing infected fescue is increased body temperature in cattle. Fescue-induced heat stress is believed to be caused by several factors. First, ergot alkaloids are known to interfere with blood flow from the core to the peripheral tissues. When this blood flow is constricted, the animal’s ability to dissipate heat through evaporative cooling is drastically impaired. One study showed a 50-percent 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 the animal’s ability to utilize copper. These alkaloids first impede plants’ copper uptake from the soil, thus inhibiting the animal’s ability to fully absorb copper during digestion. Some of the most noticeable symptoms of copper deficiency — and of fescue toxicosis — are a rough hair coat and a significant delay in shedding the winter coat. 

Coupled with decreased peripheral blood flow, this extra hair results in increased body temperature. During the heat and humidity of the summer — particularly further south — the animal’s inability to dissipate body heat results in significant heat stress, which can result in decreased feed intake, decreased weight gain and milk production, and poor breeding efficiency.

The following management techniques can help cattle deal with heat stress, particularly stress caused by fescue.

  1. Provide adequate access to cool, clean drinking water. Access to cool water is essential to helping 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 — and take note: an increase in water temperature from 70° to 95° Fahrenheit will more than double the animal’s water requirements!

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

  3. Rotate cattle to non-fescue pastures. Research has shown that, when cattle are removed from infected fescue pastures, their body temperatures recover in part within three to 12 days. 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, which is a potent source of ergot alkaloids. Avoid seedheads by grazing pastures closely or by mowing regularly if cattle aren’t able to keep up with forage growth.

  5. Provide access to high-quality mineral supplementation. This technique is beneficial in two ways. First, we know that cattle have higher water requirements during periods of heat stress, resulting in higher urine outputs. In these conditions, cattle will quickly lose essential electrolytes, such as sodium and magnesium. 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 also throws these minerals off-balance. As such, supplementing a high-quality mineral and vitamin supplement that provides adequate levels of potassium, magnesium, salt, copper, zinc and other trace minerals and vitamins will go a long way toward balancing the nutritional shortfalls caused by fescue-induced heat stress.

Nutritionally fortifying our cattle will help them be better equipped to deal with the negative effects of heat stress caused by the fescue endophyte. One of the most convenient options is SWEETLIX® CopperHead® Fescue Max minerals. These highly palatable minerals, specially formulated for cattle on fescue forages, contain essential electrolytes and a high-quality trace mineral and vitamin package. SWEETLIX CopperHead Fescue Max minerals include a combination of organic and inorganic sources of copper, zinc, manganese and cobalt for increased bioavailability.


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



Heat stress is a very real concern for cattle owners utilizing fescue pastures during the summer months. You can help your cattle regulate their body temperatures by providing them with cool water and shade and by protecting them from ingesting ergot alkaloids through limiting grazing of fescue seedheads. You can also nutritionally fortify your cattle with a product like 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.