THE UNIVERSITY OF TENNESSEE AGRICULTURAL EXTENSION SERVICE SP 439-A
Tall Fescue: Endophyte-Infected or Endophyte-Free? Gary Bates, Assistant Professor, Plant and Soil Science
all fescue is the most important Fescue toxicosis forage crop in Tennessee. It is In the late 1970s, it was discovered T grown on approximately 3.5 that the poor performance and toxicosis million acres in the state, and is used as symptoms were associated with cattle the base diet for nearly all beef cattle in grazing tall fescue infected with the fungus Tennessee. An adapted strain of this grass Neotyphodium coenophialum. The terms was discovered growing on a farm in “fescue fungus,” “endophyte,” “fungal Kentucky in 1931. The cultivar “Ken- endophyte” and “fescue endophyte” have tucky-31” was released in the early 1940s, all been used to describe this fungus. and was widely accepted by farmers “Endo” (within) plus “phyte” (plant) throughout the Southeast because of its means a plant living within another plant. wide range of adaptation, ease of estab- This fungus lives and grows between the lishment and persistence. It gained a cells of a tall fescue plant, and produces reputation as a low palatability forage that no signs or symptoms on the plant. Ef- resulted in poor animal gains and various fects of the endophyte on grazing cattle toxicosis symptoms, even though chemi- can be seen as one or more of several cal analysis indicated that tall fescue was clinical signs, including: (1) lower feed as good as any other cool-season grass. It intake, (2) lower weight gains, (3) rough was noted that dry matter intake was less hair coats during the summer, (4) lower in animals grazing tall fescue compared to milk production, (5) reduced reproductive those grazing other grasses. Early expla- performance, (6) more time spent in nations for the poor palatability and intake shade and water, and (7) necrosis of were the coarse leaves and stems, and hooves, tail, etc., commonly referred to as sharp edges on leaves. “fescue foot.” These clinical signs have been documented in various research studies conducted in Tennessee and across the Southeast (Table 1). The toxi- cosis is the result of chemicals or alkaloids produced inside the plant.
Foraging Ahead for 1a Greener Tomorrow Table 1. Effect of the tall fescue endophyte on beef cattle performance.
Endophyte level Performance measurement low high Reduction (%)
Daily gain (lb/day) 2.041 1.06 48
2.142 0.99 53
1.833 0.99 46
2.184 1.41 35
Gain per acre (lb/acre) 6191 449 27
5283 342 35
4624 371 20
Pregnancy rate (%) 955 55 42
Milk production (lb/day) 11.76 6.7 43
1 Chestnut and co-workers. 1991. Tenn. Farm and Home Science. 160:38. 2 Read and Camp. 1986. Agronomy Journal. 78:848. 3 Hoveland and co-workers. 1983. Agronomy Journal. 75:821. 4 Pedersen and co-workers. 1986. New Zealand Journal of Experimental Agriculture. 14:307. 5 Gay and co-workers. 1988. Applied Agricultural Research. 3:182. 6 Schmidt and co-workers. 1984. Alabama Experiment Station Highlights Agricultural Research. 31:17.
In beef cattle, the term “summer Mares seem to be particularly sensi- slump” has been used to refer to fescue tive to the toxins in infected tall fescue. toxicosis, because of the visual symptoms Research has shown that mares grazing that occur during most summers (e.g. endophyte-infected tall fescue have 20-30 rough hair coat, extended time in shade day longer gestation periods and more and water). Because of this, many people foaling problems than mares grazing endo- assume that fescue toxicosis is primarily a phyte-free tall fescue (Fig. 1). However, summer problem. Research has shown limited research has not indicated that the that animal performance is reduced growth rate of yearling horses is affected throughout the year, with the largest de- by the endophyte. creases in weight gains occurring during spring rather than summer.
22 Plant persistence binations of these, resulting in a more Even though the presence of the persistent plant. endophyte in tall fescue results in toxicity This discussion leads to the conclu- symptoms, there are some positive as- sion that there are problems with both pects to endophyte infection. Research infected and non-infected tall fescue. and practical experience have shown that Endophyte-infected tall fescue is persistent endophyte-infected tall fescue is more in a pasture, but results in animal toxico- persistent than endophyte-free fescue in a sis. Grazing endophyte-free tall fescue pasture. This difference became noticeable results in significantly higher animal per- as the first endophyte-free varieties were formance, but the plants are not as hardy used. Stands of endophyte-infected tall and stand life may be reduced. Because of fescue had been grazed for many years this, all producers with tall fescue pastures and were still solid. The new stands of should ask themselves two questions: endophyte-free tall fescue became weedy (1) Are my tall fescue pastures and were often lost after only a few years. infested with the endophyte? The greater persistence of infected tall (2) If my pastures are infested, what fescue is due to its enhanced ability to should I do about it? tolerate stress. The endophyte increases the tolerance of tall fescue to drought, disease, insects, grazing pressure or com-
Figure 1. Effect of the tall fescue endophyte on pregnant mares and foals.
endophyte-infected endophyte-free
12 11 11 11 11 11 11 10 10
8 7
6
4
number of animals 4
2 2 2
0 0 mares in foaling mares foals alive foals mares study problems lactating at birth surviving surviving
Putnam and co-workers. 1990. American Journal of Veterinary Research. 52:2071
3 Are my tall fescue pastures infested dures to minimize the losses caused by with the endophyte? the endophyte. This first question is the easiest to answer. Plants exhibit no outward signs of Avoiding the endophyte is the infection. One way to know the infestation method that should provide the highest level of a pasture (percentage of plants animal performance. Because of the re- that are infected) is through microscopic duced persistence of endophyte-free tall examination of tiller samples from the fescue, proper grazing management will be pasture. Past endophyte sampling has required to maintain stands. If a producer indicated that most tall fescue pastures in would rather have a pasture that requires Tennessee are highly infested, unless they less management and is willing to accept were replanted with endophyte-free tall reduced animal performance, then it may fescue. Contact your local Extension office be better to continue to use endophyte- for more information on testing for the infected tall fescue. The decision for or endophyte. against pasture re-establishment should be based on each producer’s priorities. Man- If my pastures are infested, what agement will be critical to improve perfor- should I do about it? mance, no matter which strategy is used. If less than 30 percent of the plants in a pasture are infected with the endo- Re-establishment with endophyte- phyte, there is no need to re-establish with free tall fescue endophyte-free tall fescue. Renovating If it is decided that re-establishment these pastures with red or white clover and with endophyte-free tall fescue is the best annual lespedeza will help prevent any loss option, 25 percent or less of the total in animal performance due to fescue toxi- acreage should be replanted each year. cosis. The management of these stands There are several basic steps in the proce- should be the same as for endophyte-free dure to re-establish with endophyte-free pastures (See Management of endophyte- tall fescue. free tall fescue). 1. Kill the old stand of endophyte-in- In pastures with infestation levels of fected tall fescue. This can be done by 30 percent or higher, research has shown using chemical or mechanical means. that animal performance is significantly Because of concerns about soil loss reduced by the endophyte. There may not and environmental problems with con- be any visible evidence of toxicosis, such ventional tillage, it may be best to use as fescue foot, but weight gains and con- no-till methods to establish the tall ception rates are reduced, which results in fescue. This will require chemical kill of less beef production per acre. There are the infected tall fescue. Graze or cut the two approaches that can be taken to tall fescue for hay until about May 1. reduce the effects of the endophyte on Do not allow the plants to produce grazing animals: seed. Because the fungus is spread 1. Avoid the endophyte by re-establishing through the seed, preventing seed with endophyte-free tall fescue or an- formation will prevent new endophyte- other forage species. infected plants from being established. 2. Continue to use endophyte-infected tall Spray the tall fescue with 1.5 pints of fescue and use management proce- paraquat (Gramoxone Extra®) per acre when the fescue reaches 2-3 inches in
4 height. After green regrowth is seen 4. Drill 15 pounds per acre of an endo- (usually 10-15 days), spray again with phyte-free tall fescue cultivar. Recom- 1 pint of Gramoxone Extra per acre. mended cultivars are: Alta, Kenhy, Add a non-ionic surfactant at the rate Ky-31, Phyter, and AU-Triumph. Be of 1-2 quarts per 100 gallons of spray sure to lime and fertilize according to solution. Two applications of the herbi- soil test recommendations. cide will help ensure that all of the 5. Seed red and/or white clover into the infected tall fescue is killed. For better pasture the following February. If the control of perennial, broadleaf weeds, pasture contains some hillsides that apply glyphosate (Roundup®) at the tend to be droughty during the sum- rate of 1 quart per acre. Add 2 to 4 mer, include annual lespedeza. quarts surfactant per 100 gallons of spray solution. Following these procedures should 2. Drill a sorghum-sudan grass hybrid eliminate the infected tall fescue and pro- or pearl millet into the stubble. This vide successful establishment of endo- will provide grazing or hay production phyte-free tall fescue without a large loss for the summer. in productivity. The process of spring 3. Kill the summer annual. Apply 1 pint killing, summer rotation and fall seeding of Gramoxone Extra per acre from has been the most successful method of August 15 to September 1. This will kill changing from endophyte-infected to the summer annual grass as well as endophyte-free tall fescue. any tall fescue plants that escaped the first two sprays.
5 Management of endophyte-free endophyte does not move from plant tall fescue to plant, the only way for the infesta- Once the endophyte-free tall fescue tion level of a pasture to increase is for has become established in the pasture, it infected seed to germinate and develop is important to use proper management so into an infected plant. Do not feed the stand will persist as long as possible. endophyte-infected tall fescue hay on Management should be focused on de- an endophyte-free pasture. Seedheads creasing stress and increasing the com- in hay may drop seed which can germi- petitiveness of the endophyte-free tall nate and become established. It is also fescue. important to prevent the spread of 1. Fertilize and lime according to soil infected seed by machinery. Mowers, test recommendations. A pH of 6.5 to rakes, balers, etc. should be cleaned 6.7 and an adequate nutrient supply before being brought into a endophyte- will create an environment in which the free field. endophyte-free tall fescue will be most Another source of possible contami- competitive. nation is cattle movement. Cattle graz- 2. Use proper grazing management. ing infected pastures will consume seed Research has shown that overgrazing, as they graze. Research has shown that especially during the summer and early a small percentage of this seed can fall, can result in stand decline. Rota- survive through the animal’s digestive tional grazing is the best method be- tract, and will be excreted on the cause it allows time for the grass to ground in manure. To prevent this, recover from grazing. A 3- to 4-week animals should not be moved directly period between grazings generally will from infected to non-infected pastures favor stand maintenance. For further if seedheads are present in the infected information on rotational grazing, tall fescue pasture. Place these animals obtain TN5053, “Planning an Intensive in a holding area for at least three days Grazing System,” from your local Ex- and feed a hay other than infected tall tension office. fescue hay. If continuous grazing will be used, it is important that the pastures not be Management of endophyte-infected overgrazed. Continuous close grazing tall fescue can result in severe stand loss, espe- Research has shown that infestation cially during periods of high tempera- levels as low as approximately 20 percent tures or drought. Endophyte-free tall can result in reduced weight gain in steers. fescue pastures should not be grazed If the decision is made to keep endophyte- below about 4 inches. When pasture infected tall fescue, it is possible to im- growth has slowed and overgrazing is prove performance through several man- likely, either feed hay or move cattle to agement procedures. Performance will not another pasture that has more available be as high as if the cattle were grazing forage. endophyte-free tall fescue, but manage- 3. Prevent contamination with infected ment of the cattle and pastures hopefully seed. Once an endophyte-free stand of can reduce the losses to an acceptable tall fescue has been established, it is level. important to prevent any infected seed 1. Renovate pastures with legumes. from contaminating the field. Since the Adding white and/or red clover and
66 annual lespedeza has been shown to 2. Keep pastures grazed or clipped dur- increase weight gain of steers grazing ing spring and summer. In the spring infected fescue. Legumes contain more and early summer, tall fescue pastures crude protein and are more digestible will be actively growing and producing than tall fescue. The presence of le- large amounts of forage. Research has gumes in a tall fescue pasture helps indicated that grazing these pastures reduce the level of toxins ingested close and preventing the forage from through grazing, because the legume maturing will improve animal perfor- substitutes for a portion of the tall mance on highly infested pastures. The fescue in the diet. However, improved best method to accomplish this is to diet quality and dilution of the toxin are use high stocking rates on some pas- not the only two explanations for im- tures, and use other pastures for hay proved performance. Including a le- production. As the spring and summer gume increases weight gain more than progress and forage production slows, expected if these were the only expla- pastures that have been cut for hay can nations. The reason is not clear, but be used for grazing. This should result the fact remains that adding legumes in efficient use of forage, improved to an infested tall fescue pasture will forage quality and improved animal improve animal performance. performance.
77 3. Use a controlled breeding season. Conclusions Even though fescue toxicosis occurs Many producers may feel that there throughout the year, the most evident is no use for endophyte-free tall fescue, and dramatic effects of the endophyte primarily because of earlier difficulties in occur from June through August. This stand maintenance. In many cases, it may is the time when temperatures are the be best if some fields remain in endo- highest and animal performance is the phyte-infected fescue. These may be lowest, hence the term “summer pastures that are difficult to reach with slump.” Calving time and cow breeding equipment for reseeding, or fields that will season should be adjusted so they do be abused for portions of the year. In not occur during summer. these cases, persistence is the most im- 4. Take the necessary steps to ensure a portant characteristic needed in the pas- healthy herd. Providing a complete ture. Animal performance is being lost, mineral mix, adequate protein and however. If production records indicate regular deworming are examples of that weight gains and calving percentages procedures that can be used to im- are unacceptable, the endophyte-infected prove animal performance. Even tall fescue may need to be replaced. though these will not offset fescue Proper management will allow for the toxicosis, they will ensure that animal maintenance of endophyte-free fescue performance will not be reduced by stands. Whether endophyte-free or endo- poor management. For more informa- phyte-infected tall fescue is used, proper tion on techniques for cow and calf management is essential to obtain the management, obtain a copy of the highest level of performance possible. “Tennessee Cow-Calf Handbook” from your local Extension office.
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SP439A-2.5M-9/97 (Rep) E12-2015-00-083-98 A State Partner in the Cooperative Extension System The Agricultural Extension Service offers its programs to all eligible persons regardless of race, color, age, national origin, sex or disability and is an Equal Opportunity Employer. COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS The University of Tennessee Institute of Agriculture, U.S. Department of Agriculture, and county governments cooperating in furtherance of Acts of May 8 and June 30, 1914. Agricultural Extension Service Billy G. Hicks,8 Dean