Amanda Grev, Extension Forage Specialist | Jeff Semler, Principal Agriculture Agent
University of Maryland
Sjoerd W. Duiker, Professor of Soil Management and Applied Soil Physics
Penn State Cooperative Extension
Across the Mid-Atlantic, tall fescue covers millions of acres, making it one of if not the dominant forage in many of our cool-season perennial pastures. Release of the Kentucky 31 (K-31) variety of tall fescue in the 1940s had a large impact on the forage and livestock industry. Today there are approximately 40 million acres of tall fescue pastures across the United States, much of it K-31. However, even with its widespread use this may still be the most mismanaged and misunderstood perennial forage around.
Kentucky 31 tall fescue is infected with a fungal endophyte. This fungus lives between the cells of the plant as part of a symbiotic relationship. The plant provides the endophyte with shelter and nutrients—a place for the fungus to live and reproduce. The endophyte returns the favor by producing alkaloid compounds that provide the plant with insect and drought resistance, grazing tolerance, and overall plant persistence. Regrettably, some of the alkaloids produced by an endophyte-infected plant cause poor animal performance, including low average daily gain, decreased reproductive performance, rough hair coats, elevated body temperatures, etc. Collectively, this poor performance is referred to as fescue toxicosis, and it is the reason many producers have developed a bad taste for tall fescue.
As a result of this, for many people the mere mention of tall fescue brings an automatic dismissal conjuring up bad experiences with poor animal performance. However, while fescue toxicosis can be a very real and valid concern, there can also be a time and a place for it if managed appropriately. Given the prevalence of this type of tall fescue, there are several steps producers can take to reduce fescue toxicosis and mitigate its harmful effects without a complete stand renovation. Some practical methods to achieve this are discussed below.
For several reasons, moving cattle off of fescue during the hot summer months greatly increases animal performance. First, fescue is not productive during the summer months, so moving cattle to a summer pasture simply gives them something to graze. Second, high temperatures can intensify the toxic effect of infected fescue, so moving cattle to a nontoxic pasture can help eliminate this summer slump. Research suggests that 88°F may be a threshold for significantly decreased gain. Additionally, after moving cattle should remain off of infected tall fescue for the entire summer; research also indicates a residual effect of toxicity, suggesting that rotating off of tall fescue for only one to two weeks will not greatly reduce the summer slump.
Using rotation within a grazing system will also help with avoiding close grazing. The highest levels of alkaloids are typically found in the bottom 3 inches of the fescue plant, so by leaving a greater amount of residual (ungrazed) forage you will also be limiting the animals’ exposure to the most toxic forage. As an additional bonus, grazing no shorter than 3-4 inches will also help improve stand persistence long term.
Tall fescue pastures should be grazed when the endophyte concentrations are naturally lower. The endophyte concentrates in the lower parts of the plants until the plant goes reproductive. At that time, the endophyte grows through the stem and eventually, alkaloids concentrate in the seed. Because of this, avoid grazing tall fescue when seedheads appear. Tall fescue produces seedheads during the first spring growth only, so one option is to graze the fescue aggressively in the spring to a 3-4 inch stubble height to keep it from going to seed. Another option is to clip seedheads or mow tall fescue pastures in the spring to make hay.
Timing can also be used to your advantage by stockpiling tall fescue for later grazing. Tall fescue is one of the preferred grasses for stockpiling. It grows well during the late summer and fall and its nutritional value improves in the fall as temperatures drop; thus, its feed quality is often better than other grasses in the winter. Recent research has shown that alkaloid concentrations decrease as much as 85% from December to March, making late winter grazing of stockpiled fescue a great option.
Tall fescue also has great standability in winter due to its relatively rigid leaves and robust root system. Its rigid leaves make it easier for livestock to graze during the winter months, and its robust root system withstands freezing and thawing cycles well. This characteristic also makes fescue an ideal candidate for grazing during wetter soil conditions. Furthermore, it is highly persistent, making it more likely to come back even after mistreatment or when grazed under poor conditions.
Ever heard the phrase “dilution is the solution to pollution?” The toxic effects of infected Kentucky 31 tall fescue can be diluted by adding diversity to a pasture, particularly with legumes. In the Mid-Atlantic region, common grazing legumes for interseeding include red clover, white clover, alfalfa, and birdsfoot trefoil. Each of these legumes differs in its persistence and growth characteristics, but all can be maintained with proper management. Keep in mind that legumes should be inoculated, and red clover and birdsfoot trefoil will require occasional reseeding if they are not allowed to reseed naturally every couple years.
These legumes not only help add species diversity and reduce the total toxin concentration within a pasture, but they also serve as a protein-rich companion to the fescue. Because they have the capability to fix nitrogen, large nitrogen applications are no longer needed. This is important because nitrogen fertilization, especially larger applications, has been shown to raise the alkaloid level. Red clover in particular shows promise as a companion of tall fescue because research has revealed that it produces artery-dilating isoflavones that have the ability to counteract the artery-restricting effect of alkaloids from the toxic tall fescue endophyte. Unfortunately, clovers lose their leaves sometime after a frost, so graze the fescue/clover stands prior to a hard frost and keep the pure fescue stands for stockpiling.
Supplementing with corn or other feeds also reduces the toxic effects of the endophyte on cattle. Although feeding corn at a rate of 1 percent of body weight can be effective, it may interfere with efficient forage fiber digestion. For this reason, feeding corn at a rate of 0.6 percent of body weight offers an economic compromise—it allows efficient digestion of forage fiber, lowers feed costs, and reduces the effects of toxicity. An alternate supplement is corn gluten feed, which can be fed at a higher rate without greatly reducing fiber digestion.
In summary, while these recommendations may not totally eliminate the risk of fescue toxicosis, they do provide some tools to help minimize its effects while capitalizing on the positive attributes of a tall fescue stand. When managed to its advantages, endophyte-infected tall fescue can be one of the many valuable tools in a grazers tool box.
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Roberts, C. (2000), Tall Fescue Toxicosis, University of Missouri Extension. https://extension2.missouri.edu/g4669
Poore, M., Drewnoski, M. (2010), Utilization of Stockpiled Tall Fescue in Winter Grazing Systems for Beef Cattle, Professional Animal Scientist; Apr 2010; 26, 2; Agricultural & Environmental Science Collection pg. 142
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Rogers, J. (2011), Clearing Up Some Tall Fescue Misconceptions, Noble Research Institute