On the Blog

Beware of summer slump

Tall fescue has long been associated with a syndrome known as Summer Slump. An endophyte fungus within the fescue plant produces alkaloids that cause adverse symptoms including: decreased weight gain, weight loss, decreased feed intake, reduced milk production, higher body temperature, increased respiration rates, rough hair coat, unthrifty appearance (See Figure 1), loss of blood flow to extremities, excessive salivation and poor reproductive performance. Symptoms seem to be worst during hot summer months. Luckily, there are several management options available to cattle producers to help lessen the symptoms of Summer Slump:

Figure 1. Calf exhibiting classic Summer Slump symptoms of rough, discolored hair coat; poor weight gain and unthrifty appearance. (photo by University of Tennessee)

Figure 1. Calf exhibiting classic Summer Slump symptoms of rough, discolored hair coat; poor weight gain and unthrifty appearance. (photo by University of Tennessee)

Replacement of Infected Fescue Pastures

When endophyte infection levels are too high, it may be best to replant the pastures with something else. When attempting replacement, take a "spray-and smother" approach. First spray the infected fescue with herbicide, second seed a cover crop to smother, then reseed with the desired new forage crop. The smother crop should be a fast growing annual. It is usually a good idea to renovate small portions of the farm at a time.

Rotation to Non-Fescue Pastures

Rotating cattle off of fescue pastures during hot summer months increases animal performance for several reasons. First, because fescue is a cool-season forage it stops growing during hot summer months. Rotating cattle off fescue onto growing, warm-season pastures simply gives them more to eat. Secondly, high temperatures seem to intensify the negative effects of the endophyte toxins. Moving cattle to non-infected pastures eliminates this interaction. Cattle need to stay off infected-fescue pastures for the entire summer to benefit. Taking cattle off for only a few weeks at a time will not greatly reduce summer slump symptoms.


Interseeding infected fescue pastures with legumes helps dilute the total toxins ingested as well as increasing the overall nutritional content in the pasture. These legumes must be managed to allow reseeding each year. And even with special management, many need to be manually reseeded periodically. It is also important to fertilize for the legume (limiting the amount of nitrogen) in order to allow the legumes to thrive.

Mineral Supplementation

Research has shown that copper levels are lower in endophyte-infected fescue vs. endophyte-free fescue. These differences are most pronounced late in the growing season (See Table 1). These findings support observations of decreased copper status in cattle grazing infected fescue. In research conducted in Virginia, cattle grazing endophyte-infected fescue exhibited decreased copper status as opposed to cattle grazing endophyte-free fescue. However, the magnitude of this decrease was greater than the difference between the forages. This demonstrates that the endophyte not only decreases the total amount of copper present in the fescue, but also, negatively affects bioavailability of copper for the animal. This makes sense when you consider that the typical symptoms for fescue toxicosis closely resemble those for copper deficiency. For all of these reasons, lowered copper status plays a large part in the Summer Slump syndrome. Proper intake of a high copper supplement can help alleviate some of the fescue toxicity symptoms. CRYSTALYX® Brand Supplements offer many highly palatable, self-fed supplement options designed specifically for fescue forages including: CRYSTALYX® Fescue-lyx, CRYSTALYX® Fescue-Phos and CRYSTALYX® Hi-Mag Tasco-Lyx. Visit www.crystalyx.com to view product labels and learn more.

Unfortunately, there is no silver bullet that will allow you to avoid negative effects of fescue endophyte in all situations. However, by using a combination of the management techniques mentioned above, you can greatly reduce the negative impacts of summer slump on your cattle herd.

Table 1. Mineral levels for 50 Tennessee Tall Fescue Samples (taken from Aaron, et. al. University of Tennessee).


Spring 2001

Fall 2001

Spring 2002

Magnesium, %




Potassium, %




Sulfur, %




Copper, ppm




Zinc, ppm